Evidence synthesis for constructing directed acyclic graphs (ESC-DAGs): a novel and systematic method for building directed acyclic graphs

Synthesizing Subject-matter Expertise for Variable Selection in Causal Effect Estimation: A Case Study

BACKGROUND

Causal graphs are an important tool for covariate selection but there is limited applied research on how best to create them. Here, we used data from the Coronary Drug Project trial to assess a range of approaches to directed acyclic graph (DAG) creation. We focused on the effect of adherence on mortality in the placebo arm, since the true causal effect is believed with a high degree of certainty.

METHODS

We created DAGs for the effect of placebo adherence on mortality using different approaches for identifying variables and links to include or exclude. For each DAG, we identified minimal adjustment sets of covariates for estimating our causal effect of interest and applied these to analyses of the Coronary Drug Project data.

RESULTS

When we used only baseline covariate values to estimate the cumulative effect of placebo adherence on mortality, all adjustment sets performed similarly. The specific choice of covariates had minimal effect on these (biased) point estimates, but including nonconfounding prognostic factors resulted in smaller variance estimates. When we additionally adjusted for time-varying covariates of adherence using inverse probability weighting, covariates identified from the DAG created by focusing on prognostic factors performed best.

CONCLUSION

Theoretical advice on covariate selection suggests that including prognostic factors that are not exposure predictors can reduce variance without increasing bias. In contrast, for exposure predictors that are not prognostic factors, inclusion may result in less bias control. Our results empirically confirm this advice. We recommend that hand-creating DAGs begin with the identification of all potential outcome prognostic factors.

Alcohol consumption and accelerated biological ageing in middle-aged and older people: A longitudinal study from two cohorts

BACKGROUND AND AIMS

The relationship between alcohol consumption and age-related diseases is inconsistent. Biological age (BA) serves as both a precursor and a predictor of age-related diseases; however, longitudinal associations between alcohol consumption and BA in middle-aged and older people remain unclear. We measured whether there was a longitudinal association between drinking frequency and pure alcohol intake with BA among middle-aged and older people.

DESIGN AND SETTING AND PARTICIPANTS

This study involved two prospective cohort studies, set in Southwestern China and the United Kingdom. A total of 8046 participants from the China Multi-Ethnic Cohort study (CMEC) and 5412 participants from the UK Biobank (UKB), aged 30-79 years, took part, with complete data from two waves of clinical biomarkers.

MEASUREMENTS

BA was calculated by the Klemera Doubal's method. Accelerated BA equalled BA minus chronological age. Drinking frequency and pure alcohol intake were obtained through self-reported questionnaires. Drinking frequency in the past year was classified as current non-drinking, occasional (monthly drinking) and regular (weekly drinking).

FINDINGS

Compared with consistent current non-drinkers, more frequent drinkers [CMEC: β = 0.46, 95% confidence interval (CI) = 0.13-0.80; UKB: β = 0.65, 95% CI = 0.01-1.29)], less frequent drinkers (CMEC: β = 0.62, 95% CI = 0.37-0.87; UKB: β = 0.54, 95% CI = -0.01-1.09), consistent occasional drinkers (CMEC: β = 0.51, 95% CI = 0.23-0.79; UKB: β = 0.63, 95% CI = 0.13-1.13) and consistent regular drinkers (CMEC: β = 0.56, 95% CI = 0.17-0.95; UKB: β = 0.46, 95% CI = 0.00-0.91) exhibited increased accelerated BA. A non-linear relationship between pure alcohol intake and accelerated BA was observed among consistent regular drinkers.

CONCLUSIONS

In middle-aged and older people, any change in drinking frequency and any amount of pure alcohol intake seem to be positively associated with acceleration of biological ageing, compared with maintaining abstinence.

Urea Level and Depression in Patients with Chronic Kidney Disease

Depression is common in patients with chronic kidney disease (CKD). Experimental studies suggest the role of urea toxicity in depression. We assessed both the incidence of antidepressant prescriptions and depressive symptoms (measured by CESD (Center for Epidemiologic Depression) scale) in 2505 patients with CKD (Stage 3-4) followed up over 5 years in the Chronic Kidney Disease Renal Epidemiology and Information Network (CKD-REIN) cohort. We used a joint model to assess the association between the serum urea level and incident antidepressant prescriptions, and mixed models for the association between the baseline serum urea level and CESD score over the 5-year follow-up. Among the 2505 patients, 2331 were not taking antidepressants at baseline. Of the latter, 87 started taking one during a median follow-up of 4.6 years. After adjustment for confounding factors, the hazard ratio for incident antidepressant prescription associated with the serum urea level (1.28 [95%CI, 0.94,1.73] per 5 mmol/L increment) was not significant. After adjustment, the serum urea level was associated with the mean change in the CESD score (β = 0.26, [95%CI, 0.11,0.41] per 5 mmol/L increment). Depressive symptoms burden was associated with serum urea level unlike depression events. Further studies are needed to draw firm conclusions and better understand the mechanisms of depression in CKD.

Adherence to a Healthy Diet and Risk of Multiple Carotid Atherosclerosis Subtypes: Insights from the China MJ Health Check-Up Cohort

AIM

Early-stage phenotypes of carotid atherosclerosis (CAS), such as increased carotid intima-media thickness (cIMT), and advanced-stage phenotypes, such as carotid plaque (CP), are at risk for adverse ischemic stroke events. There is limited evidence regarding the causal association between dietary patterns and the risk of CAS in Chinese adults. We therefore examined multiple dietary patterns associated with the risk of CAS and identified the optimal dietary pattern for preventing CAS.

METHODS

We analyzed data collected from the prospective MJ Health Check-up Study (2004-2020), including 13,989 participants 18-80 years of age without CAS. The dietary intake was measured using validated food frequency questionnaires, and dietary pattern scores were calculated for four a priori and four a posteriori dietary patterns. The Cox model was used to estimate the adjusted hazard ratios (HRs) relating various dietary pattern scores to the risk of CAS.

RESULTS

During 43,903.4 person-years of follow-up, 3732 incidents of increased cIMT and 2861 incident CP events were documented. Overall, the seven dietary patterns, except for the high-protein diet, exhibited significant associations with the risk of increased cIMT and CP. Comparing the highest and lowest quartiles, the a posteriori high-fiber dietary pattern (HFIDP) score demonstrated the strongest inverse associations with the risk of increased cIMT (HR 0.65 [95% confidence interval (CI) 0.59-0.71]) and CP (HR 0.65 [95% CI 0.59-0.73]); conversely, another a posteriori high-fat dietary pattern (HFADP; i.e., incorporating high-fat and processed foods) demonstrated the strongest positive associations with the risk of increased cIMT (HR 1.96 [95% CI 1.75-2.20]) and CP (HR 1.83 [95% CI 1.61-2.08]) (all p for trend < 0.01).

CONCLUSIONS

Multiple dietary patterns are significantly associated with the risk of early- and advanced-stage phenotypes of CAS. Notably, a high adherence to an HFIDP and low adherence to an HFADP may confer the greatest risk reduction for CAS.

Causal Inference in Oncology: Why, What, How and When

Oncologists are faced with choosing the best treatment for each patient, based on the available evidence from randomized controlled trials (RCTs) and observational studies. RCTs provide estimates of the average effects of treatments on groups of patients, but they may not apply in many real-world scenarios where for example patients have different characteristics than the RCT participants, or where different treatment variants are considered. Causal inference defines what a treatment effect is and how it may be estimated with RCTs or outside of RCTs with observational - or 'real-world' - data. In this review, we introduce the field of causal inference, explain what a treatment effect is and what important challenges are with treatment effect estimation with observational data. We then provide a framework for conducting causal inference studies and describe when in oncology causal inference from observational data may be particularly valuable. Recognizing the strengths and limitations of both RCTs and observational causal inference provides a way for more informed and individualized treatment decision-making in oncology.

Association of waist circumference and BMI with premature death in young and middle-aged population

Introduction

Premature death is a global health indicator, significantly impacted by obesity, especially in young and middle-aged population. Both body mass index (BMI) and waist circumference (WC) assess obesity, with WC specifically indicating central obesity and showing a stronger relationship with mortality. However, despite known associations between BMI and premature death, as well as the well-recognized correlation between WC and adverse health outcomes, the specific relationship between WC and premature death remains unclear. Therefore, focusing on young and middle-aged individuals, this study aimed to reliably estimate independent and combined associations between WC, BMI and premature death, thereby providing causal evidence to support strategies for obesity management.

Methods

This study involved 49,217 subjects aged 18-50 years in the United States from 1999 to 2018 National Health and Nutrition Examination Survey (NHANES). Independent and combined associations between WC and BMI with premature death across sex and age stratum were examined by Cox regression. Survey weighting and inverse probability weighting (IPW) were further considered to control selection and confounding bias. Robustness assessment has been conducted on both NHANES and China Health and Retirement Longitudinal Study (CHARLS) data.

Results

A linear and positive relationship between WC and all-cause premature death was found in both males and females, with adjusted HRs of 1.019 (95%CI = 1.004-1.034) and 1.065 (95%CI = 1.039-1.091), respectively. Nonlinear relationships were found with respect to BMI and all-cause premature death. For females aged 36-50 with a BMI below 28.6 kg/m2, the risk of premature death decreased as BMI increased, indicated by adjusted HRs of 0.856 (95%CI = 0.790-0.927). Joint analysis showed among people living with obesity, a larger WC increased premature death risk (HR = 1.924, 95%CI = 1.444-2.564).

Discussion

WC and BMI exhibited prominent associations with premature death in young and middle-aged population. Maintaining an appropriate WC and BMI bears significant implications for preventing premature death.

[Hypothetical Alcohol Consumption Interventions and Hepatic Steatosis: A Longitudinal Study in a Large Cohort]

Objective

Non-alcoholic fatty liver disease (NAFLD) and alcohol-associated fatty liver disease (ALD) are the most common chronic liver diseases. Hepatic steatosis is an early histological subtype of both NAFLD and ALD. Excessive alcohol consumption is widely known to lead to hepatic steatosis and subsequent liver damage. However, reported findings concerning the association between moderate alcohol consumption and hepatic steatosis remain inconsistent. Notably, alcohol consumption as a modifiable lifestyle behavior is likely to change over time, but most previous studies covered alcohol intake only once at baseline. These inconsistent findings from existing studies do not inform decision-making concerning policies and clinical guidelines, which are of greater interest to health policymakers and clinician-scientists. Additionally, recommendations on the types of alcoholic beverages are not available. Usually, assessing the effects of two or more hypothetical alcohol consumption interventions on hepatic steatosis provides answers to questions concerning the population risk of hepatic steatosis if everyone changes from heavy drinking to abstinence, or if everyone keeps on drinking moderately, or if everyone of the drinking population switches from red wine to beer? Thus, we simulated a target trial to estimate the effects of several hypothetical interventions, including changes in the amount of alcohol consumption or the types of alcoholic beverages consumed, on hepatic steatosis using longitudinal data, to inform decisions about alcohol-related policymaking and clinical care.

Methods

This longitudinal study included 12687 participants from the UK Biobank (UKB), all of whom participated in both baseline and repeat surveys. We excluded participants with missing data related to components of alcohol consumption and fatty liver index (FLI) in the baseline and the repeat surveys, as well as those who had reported liver diseases or cancer at the baseline survey. We used FLI as an outcome indicator and divided the participants into non-, moderate, and heavy drinkers. The surrogate marker FLI has been endorsed by many international organizations' guidelines, such as the European Association for the Study of the Liver. The calculation of FLI was based on laboratory and anthropometric data, including triglyceride, gamma-glutamyl transferase, body mass index, and waist circumference. Participants responded to questions about the types of alcoholic beverages, which were defined in 5 categories, including red wine, white wine/fortified wine/champagne, beer or cider, spirits, and mixed liqueurs, along with the average weekly or monthly amounts of alcohol consumed. Alcohol consumption was defined as pure alcohol consumed per week and was calculated according to the amount of alcoholic beverages consumed per week and the average ethanol content by volume in each alcoholic beverage. Participants were categorized as non-drinkers, moderate drinkers, and heavy drinkers according to the amount of their alcohol consumption. Moderate drinking was defined as consuming no more than 210 g of alcohol per week for men and 140 g of alcohol per week for women. We defined the following hypothetical interventions for the amount of alcohol consumed: sustaining a certain level of alcohol consumption from baseline to the repeat survey (e.g., none to none, moderate to moderate, heavy to heavy) and changing from one alcohol consumption level to another (e.g., none to moderate, moderate to heavy). The hypothetical interventions for the types of alcoholic beverages were defined in a similar way to those for the amount of alcohol consumed (e.g., red wine to red wine, red wine to beer/cider). We applied the parametric g-formula to estimate the effect of each hypothetical alcohol consumption intervention on the FLI. To implement the parametric g-formula, we first modeled the probability of time-varying confounders and FLI conditional on covariates. We then used these conditional probabilities to estimate the FLI value if the alcohol consumption level of each participant was under a specific hypothetical intervention. The confidence interval was obtained by 200 bootstrap samples.

Results

For the alcohol consumption from baseline to the repeat surveys, 6.65% of the participants were sustained non-drinkers, 63.68% were sustained moderate drinkers, and 14.74% were sustained heavy drinkers, while 8.39% changed from heavy drinking to moderate drinking. Regarding the types of alcoholic beverages from baseline to the repeat surveys, 27.06% of the drinkers sustained their intake of red wine. Whatever the baseline alcohol consumption level, the hypothetical interventions for increasing alcohol consumption from the baseline alcohol consumption were associated with a higher FLI than that of the sustained baseline alcohol consumption level. When comparing sustained non-drinking with the hypothetical intervention of changing from non-drinking to moderate drinking, the mean ratio of FLI was 1.027 (95% confidence interval [CI]: 0.997-1.057). When comparing sustained non-drinking with the hypothetical intervention of changing from non-drinking to heavy drinking, the mean ratio of FLI was 1.075 (95% CI: 1.042-1.108). When comparing sustained heavy drinking with the hypothetical intervention of changing from heavy drinking to moderate drinking, the mean ratio of FLI was 0.953 (95% CI: 0.938-0.968). The hypothetical intervention of changing to red wine in the UKB was associated with lower FLI levels, compared with sustained consumption of other types of alcoholic beverages. For example, when comparing sustaining spirits with the hypothetical intervention of changing from spirits to red wine, the mean ratio of FLI was 0.981 (95% CI: 0.948-1.014).

Conclusions

Regardless of the current level of alcohol consumption, interventions that increase alcohol consumption could raise the risk of hepatic steatosis in Western populations. The findings of this study could inform the formulation of future practice guidelines and health policies. If quitting drinking is challenging, red wine may be a better option than other types of alcoholic beverages in Western populations.

Effect of fluoridated water on invasive NHS dental treatments for adults: the LOTUS retrospective cohort study and economic evaluation

Background

Most water fluoridation studies were conducted on children before the widespread introduction of fluoride toothpastes. There is a lack of evidence that can be applied to contemporary populations, particularly adolescents and adults.

Objective

To pragmatically assess the clinical and cost effectiveness of water fluoridation for preventing dental treatment and improving oral health in a contemporary population of adults, using a natural experiment design.

Design

Retrospective cohort study using routinely collected National Health Service dental claims (FP17) data.

Setting

National Health Service primary dental care: general dental practices, prisons, community dental services, domiciliary settings, urgent/out-of-hours and specialised referral-only services.

Participants

Dental patients aged 12 years and over living in England (n = 6,370,280).

Intervention and comparison

Individuals exposed to drinking water with a fluoride concentration ≥ 0.7 mg F/l between 2010 and 2020 were matched to non-exposed individuals on key characteristics using propensity scores.

Outcome measures

Primary: number of National Health Service invasive dental treatments (restorations/'fillings' and extractions) received per person between 2010 and 2020. Secondary: decayed, missing and filled teeth, missing teeth, inequalities, cost effectiveness and return on investment.

Data sources

National Health Service Business Services Authority dental claims data. Water quality monitoring data.

Primary outcome

Predicted mean number of invasive dental treatments was 3% lower in the optimally fluoridated group than in the sub/non-optimally fluoridated group (incidence rate ratio 0.969, 95% CI 0.967 to 0.971), a difference of -0.173 invasive dental treatments (95% CI -0.185 to -0.161). This magnitude of effect is smaller than what most stakeholders we engaged with (n = 50/54) considered meaningful.

Secondary outcomes

Mean decayed, missing and filled teeth were 2% lower in the optimally fluoridated group, with a difference of -0.212 decayed, missing and filled teeth (95% CI -0.229 to -0.194). There was no statistically significant difference in the mean number of missing teeth per person (0.006, 95% CI -0.008 to 0.021). There was no compelling evidence that water fluoridation reduced social inequalities in treatments received or missing teeth; however, decayed, missing and filled teeth data did not demonstrate a typical inequalities gradient. Optimal water fluoridation in England in 2010-20 was estimated to cost £10.30 per person (excluding original setup costs). Mean National Health Service treatment costs for fluoridated patients 2010-20 were 5.5% lower per person, by £22.26 (95% CI -£23.09 to -£21.43), and patients paid £7.64 less in National Health Service dental charges per person (2020 prices).

Limitations

Pragmatic, observational study with potential for non-differential errors of misclassification in fluoridation assignment and outcome measurement and residual and/or unmeasured confounding. Decayed, missing and filled teeth data have not been validated. Water fluoridation cost estimates are based on existing programmes between 2010 and 2020, and therefore do not include the potentially significant capital investment required for new programmes.

Conclusions

Receipt of optimal water fluoridation between 2010 and 2020 resulted in very small health effects, which may not be meaningful for individuals, and we could find no evidence of a reduction in social inequalities. Existing water fluoridation programmes in England produced a positive return on investment between 2010 and 2020 due to slightly lower National Health Service treatment costs. These relatively small savings should be evaluated against the projected costs and lifespan of any proposed capital investment in water fluoridation, including new programmes.

Future work

National Health Service dental data are a valuable resource for research. Further validation and measures to improve quality and completeness are warranted.

Trial registrations

This trial is registered as ISRCTN96479279, CAG: 20/CAG/0072, IRAS: 20/NE/0144.

Funding

This award was funded by the National Institute for Health and Care Research (NIHR) Public Health Research programme (NIHR award ref: NIHR128533) and is published in full in Public Health Research; Vol. 12, No. 5. See the NIHR Funding and Awards website for further award information.

Gender differences in the perception of leptospirosis severity, behaviours, and Leptospira exposure risk in urban Brazil: a cross-sectional study

Background

Vulnerability to climate hazards and infectious diseases are not gender-neutral, meaning that men, women, boys, girls, and other gender identities experience different health risks. Leptospirosis, a zoonotic climate sensitive infectious disease, is commonly transmitted to humans via contact with animals and the environment, particularly soil and flood water. Gender differences in leptospiral infection risk are reported globally, with men consistently found to be at higher risk than women. However, the drivers of this difference in risk are poorly understood. Previous studies suggest that the interplay of knowledge, perceptions, and behaviours may shape differential infection risk among genders.

Methodology/Principal Findings

To examine gender differences in Leptospira exposure risk we conducted a cross-sectional serosurvey among adult participants (n = 761) in four urban, marginalised, informal settlements in the city of Salvador, Brazil. We found that seroprevalence was 14.6% and 9.4% across men and women respectively. We then applied causal inference methodology to a two-part sex-disaggregated analysis to investigate: 1) the association of perceptions and behaviours with Leptospira seropositivity and 2) the association of perceptions with behaviours. We found that men who perceived leptospirosis as extremely serious had lower odds of seropositivity, walking through sewage water, or walking barefoot, suggesting an important link between perceptions, behaviours, and exposure risk. These associations were not found in women, and these behaviours were not associated with seropositivity in men or women.

Conclusions

Our results highlight perceived severity of disease as a potential driver of behaviour in men, and perceptions of disease may be an important target for health education programs. Furthermore, our study identifies evidence gaps in the understanding of infection risks in women. As the first sex-disaggregated study investigating Leptospira infection risks, we advocate for a gendered lens in future studies to further understand risks specific to different gender identities.

Association between TB delay and TB treatment outcomes in HIV-TB co-infected patients: a study based on the multilevel propensity score method

BACKGROUND

HIV-tuberculosis (HIV-TB) co-infection is a significant public health concern worldwide. TB delay, consisting of patient delay, diagnostic delay, treatment delay, increases the risk of adverse anti-TB treatment (ATT) outcomes. Except for individual level variables, differences in regional levels have been shown to impact the ATT outcomes. However, few studies appropriately considered possible individual and regional level confounding variables. In this study, we aimed to assess the association of TB delay on treatment outcomes in HIV-TB co-infected patients in Liangshan Yi Autonomous Prefecture (Liangshan Prefecture) of China, using a causal inference framework while taking into account individual and regional level factors.

METHODS

We conducted a study to analyze data from 2068 patients with HIV-TB co-infection in Liangshan Prefecture from 2019 to 2022. To address potential confounding bias, we used a causal directed acyclic graph (DAG) to select appropriate confounding variables. Further, we controlled for these confounders through multilevel propensity score and inverse probability weighting (IPW).

RESULTS

The successful rate of ATT for patients with HIV-TB co-infection in Liangshan Prefecture was 91.2%. Total delay (OR = 1.411, 95% CI: 1.015, 1.962), diagnostic delay (OR = 1.778, 95% CI: 1.261, 2.508), treatment delay (OR = 1.749, 95% CI: 1.146, 2.668) and health system delay (OR = 1.480 95% CI: (1.035, 2.118) were identified as risk factors for successful ATT outcome. Sensitivity analysis demonstrated the robustness of these findings.

CONCLUSIONS

HIV-TB co-infection prevention and control policy in Liangshan Prefecture should prioritize early treatment for diagnosed HIV-TB co-infected patients. It is urgent to improve the health system in Liangshan Prefecture to reduce delays in diagnosis and treatment.

Exploring a Potential Interaction Between the Effect of Specific Maternal Smoking Patterns and Comorbid Antenatal Depression in Causing Postpartum Depression

Purpose

To explore a potential interaction between the effect of specific maternal smoking patterns and the presence of antenatal depression, as independent exposures, in causing postpartum depression (PPD).

Methods

This case-control study of participants with singleton term births (N = 51220) was based on data from the 2017-2018 Pregnancy Risk Assessment Monitoring System. Multivariable log-binomial regression models examined the main effects of smoking patterns and self-reported symptoms of antenatal depression on the risk of PPD on the adjusted risk ratio (aRR) scale and tested a two-way interaction adjusting for covariates selected in a directed acyclic graph (DAG). The interaction effects were measured on the additive scale using relative excess risk due to interaction (RERI), the attributable proportion of interaction (AP), and the synergy index (SI). Causal effects were defined in a counterfactual framework. The E-value quantified the potential impact of unobserved/unknown covariates, conditional on observed covariates.

Results

Among 6841 women in the sample who self-reported PPD, 35.7% also reported symptoms of antenatal depression. Out of 3921 (7.7%) women who reported smoking during pregnancy, 32.6% smoked at high intensity (≥10 cigarettes/day) in all three trimesters and 36.6% had symptoms of antenatal depression. The main effect of PPD was the strongest for women who smoked at high intensity throughout pregnancy (aRR 1.65; 95% CI: 1.63, 1.68). A synergistic interaction was detected, and the effect of all maternal smoking patterns was augmented, particularly in late pregnancy for Increasers and Reducers.

Conclusion

Strong associations and interaction effects between maternal smoking patterns and co-occurring antenatal depression support smoking prevention and cessation interventions during pregnancy to lower the likelihood of PPD.

Statistical modelling of determinants of child stunting using secondary data and Bayesian networks: a UKRI Global Challenges Research Fund (GCRF) Action Against Stunting Hub protocol paper

INTRODUCTION

Several factors have been implicated in child stunting, but the precise determinants, mechanisms of action and causal pathways remain poorly understood. The objective of this study is to explore causal relationships between the various determinants of child stunting.

METHODS AND ANALYSIS

The study will use data compiled from national health surveys in India, Indonesia and Senegal, and reviews of published evidence on determinants of child stunting. The data will be analysed using a causal Bayesian network (BN)-an approach suitable for modelling interdependent networks of causal relationships. The model's structure will be defined in a directed acyclic graph and illustrate causal relationship between the variables (determinants) and outcome (child stunting). Conditional probability distributions will be generated to show the strength of direct causality between variables and outcome. BN will provide evidence of the causal role of the various determinants of child stunning, identify evidence gaps and support in-depth interrogation of the evidence base. Furthermore, the method will support integration of expert opinion/assumptions, allowing for inclusion of the many factors implicated in child stunting. The development of the BN model and its outputs will represent an ideal opportunity for transdisciplinary research on the determinants of stunting.

ETHICS AND DISSEMINATION

Not applicable/no human participants included.

Causal diagramming for assessing human system risk in spaceflight

For over a decade, the National Aeronautics and Space Administration (NASA) has tracked and configuration-managed approximately 30 risks that affect astronaut health and performance before, during and after spaceflight. The Human System Risk Board (HSRB) at NASA Johnson Space Center is responsible for setting the official risk posture for each of the human system risks and determining-based on evaluation of the available evidence-when that risk posture changes. The ultimate purpose of tracking and researching these risks is to find ways to reduce spaceflight-induced risk to astronauts. The adverse effects of spaceflight begin at launch and continue throughout the duration of the mission, and in some cases, across the lifetime of the astronaut. Historically, research has been conducted in individual risk "silos" to characterize risk, however, astronauts are exposed to all risks simultaneously. In January of 2020, the HSRB at NASA began assessing the potential value of causal diagramming as a tool to facilitate understanding of the complex causes and effects that contribute to spaceflight-induced human system risk. Causal diagrams in the form of directed acyclic graphs (DAGs) are used to provide HSRB stakeholders with a shared mental model of the causal flow of risk. While primarily improving communication among those stakeholders, DAGs also allow a composite risk network to be created that can be tracked and configuration managed. This paper outlines the HSRB's pilot process for this effort, the lessons learned, and future goals for data-driven risk management approaches.

Causal relationships between pain, medical treatments, and knee osteoarthritis: A graphical causal model to guide analyses

OBJECTIVE

Randomized controlled trials (RCTs) are a gold standard for estimating the benefits of clinical interventions, but their decision-making utility can be limited by relatively short follow-up time. Longer-term follow-up of RCT participants is essential to support treatment decisions. However, as time from randomization accrues, loss to follow-up and competing events can introduce biases and require covariate adjustment even for intention-to-treat effects. We describe a process for synthesizing expert knowledge and apply this to long-term follow-up of an RCT of treatments for meniscal tears in patients with knee osteoarthritis (OA).

METHODS

We identified 2 post-randomization events likely to impact accurate assessment of pain outcomes beyond 5 years in trial participants: loss to follow-up and total knee replacement (TKR). We conducted literature searches for covariates related to pain and TKR in individuals with knee OA and combined these with expert input. We synthesized the evidence into graphical models.

RESULTS

We identified 94 potential covariates potentially related to pain and/or TKR among individuals with knee OA. Of these, 46 were identified in the literature review and 48 by expert panelists. We determined that adjustment for 50 covariates may be required to estimate the long-term effects of knee OA treatments on pain.

CONCLUSION

We present a process for combining literature reviews with expert input to synthesize existing knowledge and improve covariate selection. We apply this process to the long-term follow-up of a randomized trial and show that expert input provides additional information not obtainable from literature reviews alone.

The Role of Social Support and Acculturation Factors on Postpartum Mental Health Among Latinas in the MADRES Pregnancy Cohort

We examined the associations between social support and postpartum mental health in 137 U.S. and foreign-born Latinas in the MADRES pregnancy cohort. We also examined whether language, years in the U.S., and country of birth moderates these relationships. Participants were administered PROMIS support measures 1 month postpartum; the Perceived Stress and Postpartum Distress Measure 3, 6, and 12 months postpartum; and the CESD scale 12 months postpartum. Perceived stress was lower at 6 months postpartum for women reporting higher emotional (p = 0.01), informational (p = 0.03), and instrumental support (p < 0.001); and lower at 12 months postpartum for women reporting higher emotional support (p = 0.01). Distress at 6 months was lower in women reporting higher emotional support (p = 0.03). Interactions suggest that associations were stronger for mothers that speak Spanish, spent fewer years in the U.S., and were born in Central America.

Exploring the Influence of Social Class and Sex on Self-Reported Health: Insights from a Representative Population-Based Study

This study investigates the intricate interplay between social class, sex, and self-reported health (SRH) using data from the European Health Survey of Spain 2020 (EESE2020). Employing a cross-sectional design and a representative sample of 22,072 individuals, the analysis explores the persistence of disparities after adjusting for covariates, focusing on health-related variables. The study employs logistic regression models and directed acyclic graphs (DAGs) to delineate the direct effects of social class and sex on SRH, identifying a minimum adjustment set to control for confounding variables. Results reveal a gradient effect of social class on SRH, emphasizing the enduring impact of socioeconomic factors. Sex-based disparities in SRH diminish after considering additional health-related variables, highlighting the importance of a holistic approach. DAGs serve as transparent tools in disentangling complex relationships, guiding the identification of essential covariates. The study concludes that addressing health inequalities requires comprehensive strategies considering both individual health behaviours and socio-economic contexts. While recognizing limitations, such as the cross-sectional design, the findings contribute to a nuanced understanding of health disparities, informing evidence-based interventions and policies for a more equitable healthcare system.

Directed acyclic graph for epidemiological studies in childhood food allergy: Construction, user's guide, and application

Understanding modifiable prenatal and early life causal determinants of food allergy is important for the prevention of the disease. Randomized clinical trials studying environmental and dietary determinants of food allergy may not always be feasible. Identifying risk/protective factors for early-life food allergy often relies on observational studies, which may be affected by confounding bias. The directed acyclic graph (DAG) is a causal diagram useful to guide causal inference from observational epidemiological research. To date, research on food allergy has made little use of this promising method. We performed a literature review of existing evidence with a systematic search, synthesized 32 known risk/protective factors, and constructed a comprehensive DAG for early-life food allergy development. We present an easy-to-use online tool for researchers to re-construct, amend, and modify the DAG along with a user's guide to minimize confounding bias. We estimated that adjustment strategies in 57% of previous observational studies on modifiable factors of childhood food allergy could be improved if the researchers determined their adjustment sets by DAG. Future researchers who are interested in the causal inference of food allergy development in early life can apply the DAG to identify covariates that should and should not be controlled in observational studies.

Identifying potential action points for improving sleep and mental health among employees: A network analysis

BACKGROUND

Mental health issues are severe public health problems, inevitably affected by, also affecting, sleep. We used network analysis to estimate the relationship among various aspects of sleep and mental health simultaneously, and identify potential action points for improving sleep and mental health among employees.

METHODS

We used data from the baseline survey of the Chinese Cohort of Working Adults that recruited 31,105 employees between October 1st and December 31st, 2021. The mental health included anxiety (measured by the Generalized Anxiety Disorder-7), depression (Patient Health Questionnaire-9]), loneliness (Short Loneliness Scale), well-being (Short Scales of Flourishing and Positive and Negative Feelings), and implicit health attitude (Lay Theory of Health Measures). Seven dimensions of sleep were assessed by the Pittsburgh Sleep Quality Index. An undirected network model and two directed network approaches, including Bayesian Directed Acyclic Graphs (DAGs) and Evidence Synthesis for Constructing-DAGs (ESC-DAGs), were applied to investigate associations between variables and identify key variables.

RESULTS

Depression, daytime dysfunction, and well-being were the "bridges" connecting the domains of sleep and mental health in the undirected network, and were in the main pathway connecting most variables in the Bayesian DAG. Anxiety constituted a gateway that activated other sleep and mental health variables, with sleep duration and implicit health attitude forming end points of the pathway. Similar directed pathways were confirmed in the ESC-DAG.

CONCLUSION

Our network study suggests anxiety, depression, well-being, and daytime dysfunction may be potential action points in preventing the development of poor sleep and mental health outcomes for employees.

Dietary patterns and metabolic dysfunction-associated fatty liver disease in China's multi-ethnic regions

BACKGROUND

The prevalence of metabolic dysfunction-associated fatty liver disease (MAFLD) has been rising rapidly in western China. Diet acts as an effective therapy for MAFLD. However, there has been scarce research on the association between a posteriori diet patterns (DPs) and MAFLD in this region.

METHOD

We identified three a posteriori DPs which were "Sichuan Basin pattern" characterized by a high intake of fish/seafood, poultry, fresh fruit and vegetables, indicating a balanced and modern DP; the "Yunnan-Guizhou Plateau dietary pattern" characterized mainly by a high intake of animal oil and salt, indicating an agricultural and poor DP; and the "Qinghai-Tibet Plateau dietary pattern" characterized by a high intake of coarse grains, wheat products, tubers and tea, respectively, indicating a high-altitude DP. Then, we performed marginal structural models that combined logistic regression and inverse probability exposure weighting (IPEW) to examine the associations between MAFLD and these a posteriori DPs.

RESULT

We found the "Yunnan-Guizhou Plateau dietary pattern" revealed stronger positive association (OR = 1.50, 95% CI 1.40-1.60) with MAFLD than that of the "Qinghai-Tibet Plateau dietary pattern" (OR = 1.21, 95% CI 1.14-1.30). In contrast, the "Sichuan Basin dietary pattern" showed no significant association with MAFLD. In the further stratified analysis, we found those above associations were stronger in ethnic minorities and rural residents than their counterparts.

CONCLUSION

Our study implied the unfavourable effects of "Yunnan-Guizhou Plateau dietary pattern" on MAFLD and provided evidence that reducing the intake of oil and sodium may be optimal for MAFLD control in the multi-ethnic region in western China.

In-Hospital Formula Feeding Hindered Exclusive Breastfeeding: Breastfeeding Self-Efficacy as a Mediating Factor

Breastfeeding self-efficacy (BSE), defined as a mother's confidence in her ability to breastfeed, has been confirmed to predict the uptake of exclusive breastfeeding (EBF). Early experiences during the birth hospital stay, especially in-hospital formula feeding (IHFF), can impact both EBF and maternal breastfeeding confidence. Therefore, our objective was to examine the association between IHFF and EBF outcomes and investigate whether this association is influenced by BSE. The study included 778 infants from a larger cohort study conducted in 2021, with a one-year follow-up in rural areas of Sichuan Province, China. We used a causal mediation analysis to estimate the total effect (TE), natural direct (NDE), and nature indirect effects (NIE) using the paramed command in Stata. Causal mediation analyses revealed that IHFF was negatively associated with EBF (TE odds ratio = 0.47; 95% CI, 0.29 to 0.76); 28% of this association was mediated by BSE. In the subgroup analysis, there were no significant differences in the effects between parity subgroups, as well as between infant delivery subgroups. Our study found that IHFF hindered later EBF and that BSE mediated this association. Limiting the occurrence of in-hospital formula feeding or improving maternal breastfeeding self-efficacy is likely to improve exclusive breastfeeding outcomes.

Mediation and longitudinal analysis to interpret the association between clozapine pharmacokinetics, pharmacogenomics, and absolute neutrophil count

Clozapine is effective at reducing symptoms of treatment-resistant schizophrenia, but it can also induce several adverse outcomes including neutropenia and agranulocytosis. We used linear mixed-effect models and structural equation modelling to determine whether pharmacokinetic and genetic variables influence absolute neutrophil count in a longitudinal UK-based sample of clozapine users not currently experiencing neutropenia (N = 811). Increased daily clozapine dose was associated with elevated neutrophil count, amounting to a 133 cells/mm3 rise per standard deviation increase in clozapine dose. One-third of the total effect of clozapine dose was mediated by plasma clozapine and norclozapine levels, which themselves demonstrated opposing, independent associations with absolute neutrophil count. Finally, CYP1A2 pharmacogenomic activity score was associated with absolute neutrophil count, supporting lower neutrophil levels in CYP1A2 poor metabolisers during clozapine use. This information may facilitate identifying at-risk patients and then introducing preventative interventions or individualised pharmacovigilance procedures to help mitigate these adverse haematological reactions.

Estimating the effect of physical activity on cognitive function within the UK Biobank cohort

BACKGROUND

Physical activity (PA) has been associated with benefits for cognitive function (CF), but previous estimates of the strength of this relationship may have been biased due to limitations in statistical modelling practices that are common among observational studies. We aimed to address this by using a rigorously constructed conceptual causal model to guide an empirical analysis estimating the effect of PA on CF in the UK Biobank cohort of middle-aged and older adults.

METHODS

This study analysed a subsample of 334 227 adults from the UK Biobank prospective cohort study. PA was measured subjectively by self-report and by device using accelerometry, and CF was measured using objective cognitive tests. Composite CF measures were derived to represent general and domain-specific performance. Effect coefficients were estimated using regression models, adjusting for a wide range of confounders specified by the assumed causal model, including genetic risk factors, and relevant health, sociodemographic and behavioural variables from across the lifespan.

RESULTS

Results indicated very small effect sizes (standardized mean difference estimates all <0.01) of inconsistent direction, for both cross-sectional and longitudinal analyses.

CONCLUSIONS

The expected protective effect of PA on CF was not observed. This may reflect selection bias within UK Biobank, or the relatively young age of the sample at follow-up.

Is COPD mortality in South China causally linked to the long-term PM1 exposure? Evidence from a large community-based cohort

BACKGROUND

Long-term ambient particulate matter (PM) exposure has been found associated with chronic obstructive pulmonary disease (COPD) mortality in an increasing body of research. However, limited evidence was available on the potential causal links between PM1 and COPD mortality, especially in highly exposed areas.

OBJECTIVES

To examine the COPD mortality risk following long-term ambient PM1 exposure in south China.

METHODS

The cohort included 580,757 participants recruited during 2009-2015. Satellite-based annual concentrations of PM1 were estimated at a spatial resolution of 1 km × 1 km and assigned to each participant based on their residential addresses. We analyzed the potential causal links between time-varying PM1 exposure and COPD mortality using marginal structural cox models within causal frameworks. Stratified analyses were also performed to identify the potential susceptible groups.

RESULTS

The annual average PM1 concentration continuously decreased over time. After adjusting for confounders, each 1 μg/m3 increase in PM1 concentration corresponded to an 8.1 % (95% confidence interval: 6.4-9.9 %) increment in the risk of COPD mortality. The impact of PM1 was more pronounced among the elderly and those with low exercise frequency, with a 1.9-6.9 % higher risk than their counterparts. We further observed a 0.1-9.7 % greater risk among those who lived in lower greenness settings. Additionally, we observed higher effect estimates in participants with long-term low PM1 exposure compared to the general population.

CONCLUSIONS

COPD mortality risk significantly increased following long term ambient PM1 exposure, particularly among groups with certain demographics or long-term low exposure.

Perinatal outcomes in singleton live births after blastocyst transfer: an analysis of 60,926 in vitro fertilization cycles from the United Kingdom

OBJECTIVE

To compare perinatal outcomes between singleton live births after blastocyst-stage and cleavage-stage fresh embryo transfer using data from all United Kingdom licensed fertility clinics.

DESIGN

A cohort study.

SETTING

Not applicable.

PATIENT(S)

A total of 60,926 in vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI) cycles resulting in a singleton live birth after blastocyst-stage and cleavage-stage fresh embryo transfer between 2012 and 2018.

INTERVENTION(S)

Baseline characteristics between IVF/ICSI blastocyst and cleavage-stage transfer groups were compared using the χ2 test for categorical/dichotomized variables and the Mann-Whitney test for continuous variables. Statistical significance was set at <.05. Association between perinatal outcomes and blastocyst transfer compared with cleavage-stage transfer was assessed using multinomial logistic regression, adjusting for confounders selected using directed acyclic graphs (95% confidence interval [CI], adjusted relative risk ratio [aRRR]). A subgroup analysis included cycles in women undergoing their first IVF/ICSI cycle.

MAIN OUTCOMES MEASURE(S)

Gestational age at birth and birth weight.

RESULT(S)

The blastocyst group comprised 42,677 IVF/ICSI cycles and cleavage-stage group 18,249 cycles. There was likely little to no difference in the risk of preterm (aRRR, 1.07; 95% CI, 1.00-1.15) and very preterm birth (aRRR, 1.05; 95% CI, 0.91-1.21) in singleton live births after fresh blastocyst and cleavage-stage transfer. Risks of low birth weight (aRRR, 1.02; 95% CI, 0.95-1.09), very low birth weight (aRRR 0.96; 95% CI, 0.83-1.11), high birth weight (aRRR, 0.97; 95% CI, 0.90-1.04), and very high birth weight (aRRR, 0.91; 95% CI, 0.77-1.08) were likely similar between the groups. The findings were consistent in the subgroup analysis.

CONCLUSION(S)

Fresh blastocyst transfer does not appear to have a negative impact on gestational age at birth and birth weight in singleton live births compared with fresh cleavage-stage transfer.

Key predictors of psychological distress and wellbeing in Australian frontline healthcare workers during COVID-19 (Omicron wave)

Introduction

The COVID-19 pandemic has led to significant challenges for frontline healthcare workers' (FHW), raising many mental health and wellbeing concerns for this cohort. To facilitate identification of risk and protective factors to inform treatment and interventions, this study investigated key predictors of psychological distress and subjective wellbeing in FHWs.

Methods

During the Omicron wave of the COVID-19 pandemic (January 2022), Victorian (Australia) doctors, nurses, allied health and non-medical staff from Emergency Departments, Intensive Care units, Aged Care, Hospital In The Home, and COVID Wards completed a cross-sectional survey consisting of the Kessler 6 item (Psychological Distress), Personal Wellbeing Index (Subjective Wellbeing), Coronavirus Health Impact Survey tool (COVID-19 related factors) and occupational factors. Multivariable linear regressions were used to evaluate unadjusted and adjusted associations. Relative weight analysis was used to compare and identify key predictors.

Results

Out of 167 participants, 18.1% screened positive for a probable mental illness and a further 15.3% screened positive for low wellbeing. Key risk factors for greater psychological distress included COVID infection worries, relationship stress and younger age. For both psychological distress and lower wellbeing, health status and supervisor support were key protective factors, while infection risks were key risk factors. Only positive changes in relationship quality was protective of lower wellbeing.

Conclusion

This study highlights the significance of social determinants and individual level factors alongside work related factors, in influencing FHWs' mental health and wellbeing during public health crises, such as the COVID-19 pandemic. Findings suggest that future interventions and supports should take a more holistic approach that considers work, social and individual level factors when supporting FHWs' mental health and wellbeing.

The effect of geographical variation in income measures on measles-mumps-rubella uptake and coverage in England; a protocol for an ecological study

Measles is a vaccine-preventable disease whose vaccine was introduced in England in 1988, however, Measles outbreaks have still been occurring in the country. Consequently, the World Health Organization (WHO) removed the elimination status of Measles in 2019 from England and the whole United Kingdom. Noticeably, MMR vaccination coverage in England is below the recommended threshold with geographical variations across local authorities (LA). The research into the effect of income disparities on MMR vaccine coverage was insufficiently examined. Therefore, an ecological study will be conducted aiming at determining whether there is a relationship between income deprivation measures and MMR vaccine coverage in upper-tier local authorities in England. This study will be using 2019 publicly available vaccination data for children who were eligible for the MMR vaccine by their second and fifth birthday in 2018/2019. The effect of spatial clustering of income level on vaccination coverage will also be assessed. Vaccination coverage data will be obtained from "Cover of Vaccination Evaluated Rapidly (COVER)". Income deprivation score, Deprivation gap, and Income Deprivation Affecting Children Index will be obtained from Office for National Statistics and Moran's Index will be generated using RStudio. Rural/urban LA classification and mothers' education will be included as possible confounding factors. Additionally, the live births rate per mothers' age group will be included as a proxy for the mothers' age variation in different LA. Multiple linear regression will be used after testing the relevant assumptions, using SPSS software. Moran's I together with income deprivation score will be analysed through regression and mediation analysis. This study will help in determining whether income level is a determinant of MMR vaccination uptake and coverage in LA in England which would help policymakers in designing targeted campaigns, thus preventing measles outbreaks in the future.

How does facilitation in healthcare work? Using mechanism mapping to illuminate the black box of a meta-implementation strategy

BACKGROUND

Healthcare facilitation, an implementation strategy designed to improve the uptake of effective clinical innovations in routine practice, has produced promising yet mixed results in randomized implementation trials and has not been fully researched across different contexts.

OBJECTIVE

Using mechanism mapping, which applies directed acyclic graphs that decompose an effect of interest into hypothesized causal steps and mechanisms, we propose a more concrete description of how healthcare facilitation works to inform its further study as a meta-implementation strategy.

METHODS

Using a modified Delphi consensus process, co-authors developed the mechanistic map based on a three-step process. First, they developed an initial logic model by collectively reviewing the literature and identifying the most relevant studies of healthcare facilitation components and mechanisms to date. Second, they applied the logic model to write vignettes describing how facilitation worked (or did not) based on recent empirical trials that were selected via consensus for inclusion and diversity in contextual settings (US, international sites). Finally, the mechanistic map was created based on the collective findings from the vignettes.

FINDINGS

Theory-based healthcare facilitation components informing the mechanistic map included staff engagement, role clarification, coalition-building through peer experiences and identifying champions, capacity-building through problem solving barriers, and organizational ownership of the implementation process. Across the vignettes, engagement of leaders and practitioners led to increased socialization of the facilitator's role in the organization. This in turn led to clarifying of roles and responsibilities among practitioners and identifying peer experiences led to increased coherence and sense-making of the value of adopting effective innovations. Increased trust develops across leadership and practitioners through expanded capacity in adoption of the effective innovation by identifying opportunities that mitigated barriers to practice change. Finally, these mechanisms led to eventual normalization and ownership of the effective innovation and healthcare facilitation process.

IMPACT

Mapping methodology provides a novel perspective of mechanisms of healthcare facilitation, notably how sensemaking, trust, and normalization contribute to quality improvement. This method may also enable more efficient and impactful hypothesis-testing and application of complex implementation strategies, with high relevance for lower-resourced settings, to inform effective innovation uptake.

Associations between major dietary patterns and blood pressure among Southwest Chinese: A cross-sectional analysis based on the China Multi-Ethnic Cohort (CMEC) study

BACKGROUND AND AIMS

In the less developed multi-ethnic regions (LEMRs) of Southwest China, the associations between dietary patterns and blood pressure (BP) values remain unclear. We aimed to investigate such associations and related effect modifiers.

METHODS AND RESULTS

This study included 81,433 participants from the China Multi-Ethnic Cohort Study. Dietary intakes during the year before the interview were measured with the Quantitative Food Frequency Questionnaire. Three major dietary patterns that were highly in line with geographical and ethnic distributions of the study population, i.e., "Sichuan Basin," "Yunnan-Guizhou Plateau," and "Qinghai-Tibet Plateau," were derived using principal component factor analysis. The multilinear regression model combined with inverse probability of exposure weighting was used to estimate the associations between dietary patterns and BP values. Comparing the highest with the lowest quintiles, the Sichuan Basin dietary pattern (characterized by urban lifestyles) was associated with 2.67 mmHg lower systolic blood pressure (SBP) (95% CI: -3.07 to -2.27) and 0.89 mmHg lower diastolic blood pressure (95% CI: -1.12 to -0.65). In contrast, both the Yunnan-Guizhou Plateau (characterized by agricultural lifestyles) and the Qinghai-Tibet Plateau dietary patterns (characterized by nomadic lifestyles) showed positive associations with BP. In the stratified analysis, the associations between dietary patterns and SBP were significantly stronger in women than in men for all three kinds of dietary patterns.

CONCLUSION

Both major dietary patterns and their associations with BP showed a substantial disparity in LEMRs of Southwest China. Dietary patterns in regions of higher socioeconomic status are more conducive to reducing the rising of BP, especially for women and urban residents, which might provide insights into the BP control in LEMRs of Southwest China.

Age-varying relationships between family support and depressive symptoms in Chinese community-dwelling older adults

BACKGROUND

Adequate family support is an important factor in reducing the risk of depressive symptoms in older adults. We aimed to explore the age-varying relationships of family support and depressive symptoms in community-dwelling older adults.

METHODS

A total of 22,163 person-waves of older adults aged 60 to 85 years from the China Health and Retirement Longitudinal Survey were included. Depressive symptoms were assessed by the Center for Epidemiological Studies Depression Scale. Family support was divided into instrumental family support and emotional family support. A Time-Varying Effects Model was utilized to analyze the age-varying relationships.

RESULTS

There were age-varying relationships between family support and depressive symptoms in community-dwelling older adults. Around age 70 was an important turning point of age. In instrumental family support, access to living care can reduce the risk of depressive symptoms in almost all age groups. At least medium-level financial support was required to be protective against depressive symptoms, and high-level financial support was necessary after age 70. In emotional family support, meeting children with high frequency was significantly associated with a lower risk of depressive symptoms before age 70. Contacting children with low or medium frequency added the risk of depressive symptoms before age 70.

LIMITATIONS

Limited sample size of participants aged 80 years and above, lack of assessment for expectations of family support.

CONCLUSIONS

Providing the appropriate type and intensity of family support for older adults at a suitable age was encouraged. Future research should further verify and explicate the age-varying relationships longitudinally.

Maternal Dietary Inflammatory Potential and Offspring Birth Outcomes in a Chinese Population

BACKGROUND

Chronic inflammation perturbations during pregnancy may impact fetal growth; however, research on the association between dietary inflammation and birth outcomes is limited and inconsistent.

OBJECTIVES

This study seeks to assess whether the dietary inflammatory potential is related to birth outcomes among pregnant women in China.

METHODS

A total of 7194 mothers aged 17-46 y and their infants in China were included in this cross-sectional study. Dietary intake was assessed by a FFQ, which yielded scores on the energy-adjusted dietary inflammatory index (E-DII). Birth outcomes included birth weight, gestational age, birth weight z score, low birth weight (LBW), macrosomia, preterm birth, small-for-gestational-age (SGA), large-for-gestational-age (LGA), and birth defects. Generalized estimating equation and restricted cubic spline fit each outcome on continuous or quartiles of E-DII after adjusting for covariates.

RESULTS

The maternal E-DII ranged from -5.35 to 6.77. Overall, birth weight and gestation age (mean ± SD) were 3267.9 ± 446.7 g and 39.6 ± 1.3 wk, respectively, and the birth weight z score was 0.02 ± 1.14. A total of 3.2% of infants were born with LBW, 6.1% with macrosomia, 3.0% were preterm birth, 10.7% were born SGA, 10.0% were born LGA, and 2.0% were born with birth defects. E-DII was associated with a 9.8 g decrease in birth weight (95% CI: -16.9, -2.6) and a 1.09-fold (95% CI: 1.01, 1.18), 1.11-fold (95% CI: 1.02, 1.21), and 1.12-fold (95% CI: 1.02, 1.24) greater risk of LBW, preterm birth, and birth defects, respectively. The maternal E-DII score was nonlinearly associated with gestational age (P for linearity = 0.009, P for curvature = 0.044).

CONCLUSIONS

Among pregnant Chinese women, proinflammatory diets during pregnancy were related to reduced offspring birth weight and an increased risk of LBW, preterm birth, and birth defects. These findings might inform potential prevention strategies for pregnant women in China.

Controlling time-varying confounding in difference-in-differences studies using the time-varying treatments framework

This article clarifies how the biostatistical literature on time-varying treatments (TVT) can provide tools for dealing with time-varying confounding in difference-in-differences (DiD) studies. I use a simulation study to compare the bias and standard error of inverse probability weighting estimators from the TVT framework, a DiD framework, and hybrid approaches that combine ideas from both frameworks. I simulated longitudinal data with treatment effect heterogeneity over multiple time points using linear and logistic models. Simulation settings looked at both time-invariant confounders and time-varying confounders affected by prior treatment. Estimators that combined ideas from both frameworks had lower bias than standard TVT and DiD estimators when assumptions were unmet. The TVT framework provides estimation tools that can complement DiD tools in a wide range of applied settings. It also provides alternate estimands for consideration in policy settings.

Parental feeding practices as potential moderating or mediating factors in the associations between children's early and later growth

BACKGROUND

Given inconsistent results in the literature, our objective was to examine the role of early parental feeding practices in children's growth.

METHODS

Analyses were based on 1245 children from the EDEN mother-child cohort. Parental feeding practices were assessed at the 2-year follow-up by using the Comprehensive Feeding Practices Questionnaire. International Obesity Task Force BMI z-scores were derived from weight and height assessed at 2, 4, 6, and 8 years. Associations between parental feeding practices and child BMI z-scores at 4, 6 and 8 years were assessed by multivariable linear regressions, notably adjusted for 2-year BMI z-score. Analyses were stratified by child sex when relevant. Moreover, interaction and mediation analyses were respectively performed to assess whether parental feeding practices could moderate or mediate the associations between early and later growth.

RESULTS

For a given BMI z-score at 2 years, parental restriction for weight at 2 years was positively associated with child BMI z-scores from 4 to 8 years (at 8 years: β [95% CI] = 0.09 [0.01; 0.16]). Among boys only, high use of food as a reward was positively associated with later BMI z-scores (at 8 years: β [95% CI] = 0.15 [0.03; 0.27]). Parental feeding practices were not moderating factors in the associations between early and later growth. Parental restriction for weight was a mediating factor in the associations between 2-year BMI z-score and BMI z-scores up to 8 years (mediation: 2.69% [0.27%; 5.11%] of the total effect at 8 years).

CONCLUSIONS

Restriction for weight reasons, often used by parents in response to the child's high appetite in infancy, appears to lie on the pathway between early and later BMI, but not restriction for health, suggesting that parental way of restricting the child's food intake matters.

Directed acyclic graphs in perioperative observational research-A systematic review and critique against best practice recommendations

The Directed Acyclic Graph (DAG) is a graph representing causal pathways for informing the conduct of an observational study. The use of DAGs allows transparent communication of a causal model between researchers and can prevent over-adjustment biases when conducting causal inference, permitting greater confidence and transparency in reported causal estimates. In the era of 'big data' and increasing number of observational studies, the role of the DAG is becoming more important. Recent best-practice guidance for constructing a DAG with reference to the literature has been published in the 'Evidence synthesis for constructing DAGs' (ESC-DAG) protocol. We aimed to assess adherence to these principles for DAGs constructed within perioperative literature. Following registration on the International Prospective Register of Systematic Reviews (PROSPERO) and with adherence to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) reporting framework for systematic reviews, we searched the Excerpta Medica dataBASE (Embase), the Medical Literature Analysis and Retrieval System Online (MEDLINE) and Cochrane databases for perioperative observational research incorporating a DAG. Nineteen studies were included in the final synthesis. No studies demonstrated any evidence of following the mapping stage of the protocol. Fifteen (79%) fulfilled over half of the translation and integration one stages of the protocol. Adherence with one stage did not guarantee fulfilment of the other. Two studies (11%) undertook the integration two stage. Unmeasured variables were handled inconsistently between studies. Only three (16%) studies included unmeasured variables within their DAG and acknowledged their implication within the main text. Overall, DAGs that were constructed for use in perioperative observational literature did not consistently adhere to best practice, potentially limiting the benefits of subsequent causal inference. Further work should focus on exploring reasons for this deviation and increasing methodological transparency around DAG construction.

Development and application of an evidence-based directed acyclic graph to evaluate the associations between metal mixtures and cardiometabolic outcomes

Objectives

Specifying causal models to assess relationships among metal mixtures and cardiometabolic outcomes requires evidence-based models of the causal structures; however, such models have not been previously published. The objective of this study was to develop and evaluate a directed acyclic graph (DAG) diagraming metal mixture exposure and cardiometabolic outcomes.

Methods

We conducted a literature search to develop the DAG of metal mixtures and cardiometabolic outcomes. To evaluate consistency of the DAG, we tested the suggested conditional independence statements using linear and logistic regression analyses with data from the San Luis Valley Diabetes Study (SLVDS; n=1795). We calculated the proportion of statements supported by the data and compared this to the proportion of conditional independence statements supported by 1,000 DAGs with the same structure but randomly permuted nodes. Next, we used our DAG to identify minimally sufficient adjustment sets needed to estimate the association between metal mixtures and cardiometabolic outcomes (i.e., cardiovascular disease, fasting glucose, and systolic blood pressure). We applied them to the SLVDS using Bayesian kernel machine regression, linear mixed effects, and Cox proportional hazards models.

Results

From the 42 articles included in the review, we developed an evidence-based DAG with 74 testable conditional independence statements (43 % supported by SLVDS data). We observed evidence for an association between As and Mn and fasting glucose.

Conclusions

We developed, tested, and applied an evidence-based approach to analyze associations between metal mixtures and cardiometabolic health.

Factors associated with successful reintegration for male offenders: a systematic narrative review with implicit causal model

Objectives

This systematic review explored factors associated with successful reintegration into the community for male offenders and investigated which factors may be causally related to reintegration.

Methods

Database searches were conducted in November 2021; a narrative synthesis and associated causal model with directed acyclic graph (DAG) was used to analyse the factors of reintegration.

Results

Thirty-four studies met the inclusion criteria. Risk-Need-Responsivity-based interventions had the strongest evidence for reducing post-release offending. Fourteen good-quality studies met the inclusion criteria. The DAG shows six exposure variables (prison visits, witnessing victimisation, recovery perception, risk assessment, in-prison treatment, and pre-prison health) which link to several post-release outcomes (criminal justice outcomes, drug use, mental health, housing, and reintegration barriers) and confounding variables (demographics, offending history, prior reintegration barriers, substance misuse and attitudes).

Conclusions

The review identified factors that may be causally related to reintegration for male offenders and warrant further empirical investigation.

The effect of time-varying capacity utilization on 14-day in-hospital mortality: a retrospective longitudinal study in Swiss general hospitals

BACKGROUND

High bed-occupancy (capacity utilization) rates are commonly thought to increase in-hospital mortality; however, little evidence supports a causal relationship between the two. This observational study aimed to assess three time-varying covariates-capacity utilization, patient turnover and clinical complexity level- and to estimate causal effect of time-varying high capacity utilization on 14 day in-hospital mortality.

METHODS

This retrospective population-based analysis was based on routine administrative data (n = 1,152,506 inpatient cases) of 102 Swiss general hospitals. Considering the longitudinal nature of the problem from available literature and expert knowledge, we represented the underlying data generating mechanism as a directed acyclic graph. To adjust for patient turnover and patient clinical complexity levels as time-varying confounders, we fitted a marginal structure model (MSM) that used inverse probability of treatment weights (IPTWs) for high and low capacity utilization. We also adjusted for patient age and sex, weekdays-vs-weekend, comorbidity weight, and hospital type.

RESULTS

For each participating hospital, our analyses evaluated the ≥85th percentile as a threshold for high capacity utilization for the higher risk of mortality. The mean bed-occupancy threshold was 83.1% (SD 8.6) across hospitals and ranged from 42.1 to 95.9% between hospitals. For each additional day of exposure to high capacity utilization, our MSM incorporating IPTWs showed a 2% increase in the odds of 14-day in-hospital mortality (OR 1.02, 95% CI: 1.01 to 1.03).

CONCLUSIONS

Exposure to high capacity utilization increases the mortality risk of inpatients. Accurate monitoring of capacity utilization and flexible human resource planning are key strategies for hospitals to lower the exposure to high capacity utilization.

Association of dietary patterns with obesity and metabolically healthy obesity phenotype in Chinese population: a cross-sectional analysis of China Multi-Ethnic Cohort Study

Metabolically healthy obesity (MHO) might be an alternative valuable target in obesity treatment. We aimed to assess whether alternative Mediterranean (aMED) diet and Dietary Approaches to Stop Hypertension (DASH) diet were favourably associated with obesity and MHO phenotype in a Chinese multi-ethnic population. We conducted this cross-sectional analysis using the baseline data of the China Multi-Ethnic Cohort study that enrolled 99 556 participants from seven diverse ethnic groups. Participants with self-reported cardiometabolic diseases were excluded to eliminate possible reverse causality. Marginal structural logistic models were used to estimate the associations, with confounders determined by directed acyclic graph (DAG). Among 65 699 included participants, 11·2 % were with obesity. MHO phenotype was present in 5·7 % of total population and 52·7 % of population with obesity. Compared with the lowest quintile, the highest quintile of DASH diet score had 23 % decreased odds of obesity (OR = 0·77, 95 % CI 0·71, 0·83, P_trend < 0·001) and 27 % increased odds of MHO (OR = 1·27, 95 % CI 1·10, 1·48, P_trend = 0·001) in population with obesity. However, aMED diet showed no obvious favourable associations. Further adjusting for BMI did not change the associations between diet scores and MHO. Results were robust to various sensitivity analyses. In conclusion, DASH diet rather than aMED diet is associated with reduced risk of obesity and presents BMI-independent metabolic benefits in this large population-based study. Recommendation for adhering to DASH diet may benefit the prevention of obesity and related metabolic disorders in Chinese population.

Population-Level Analysis of Appropriateness of End-of-Life Care for Children with Neurologic Conditions

OBJECTIVE

The objective of this study was to measure the appropriateness of end-of-life care for children who died with neurologic conditions.

STUDY DESIGN

Based on linked routinely collected databases, we conducted a population-level decedent retrospective cohort study of children with neurologic conditions who died in Belgium between 2010 and 2017. We measured a set of 22 face-validated quality indicators. The set concerns 12 indicators of potentially appropriate end-of-life care (eg, specialized comfort medication, physician contact, continuous care) and 10 indicators of potentially inappropriate end-of-life care (eg, diagnostic tests, phlebotomy). We performed ANOVA for predictors (age, sex, disease category, nationality, having siblings, year of death) for scales of appropriate and inappropriate care.

RESULTS

Between 2010 and 2017, 139 children with neurologic conditions died in Belgium. For potentially appropriate care, in the last 30 days, 76% of children received clinical care, 55% had continuous care relationships, 17% had contact with a general physician, 8% of children received specialized comfort medication, and 14% received care from a palliative care team. For potentially inappropriate care, in the last 14 days, 45% had blood drawn and 27% were admitted to intensive care unit.

CONCLUSIONS

Our study found indications of appropriate as well as inappropriate end-of-life care for children who died with neurologic conditions. These findings reveal a substantial margin for potential quality improvement, in regard to palliative care provision, multidisciplinary care, financial support, specialized comfort medication, clinical follow-up, general physician contact, diagnostics, and blood drawing.

The association between early-life gut microbiota and childhood respiratory diseases: a systematic review

Data from animal models suggest a role of early-life gut microbiota in lung immune development, and in establishing susceptibility to respiratory infections and asthma in humans. This systematic review summarises the association between infant (ages 0-12 months) gut microbiota composition measured by genomic sequencing, and childhood (ages 0-18 years) respiratory diseases (ie, respiratory infections, wheezing, or asthma). Overall, there was evidence that low α-diversity and relative abundance of particular gut-commensal bacteria genera (Bifidobacterium, Faecalibacterium, Ruminococcus, and Roseburia) are associated with childhood respiratory diseases. However, results were inconsistent and studies had important limitations, including insufficient characterisation of bacterial taxa to species level, heterogeneous outcome definitions, residual confounding, and small sample sizes. Large longitudinal studies with stool sampling during the first month of life and shotgun metagenomic approaches to improve bacterial and fungal taxa resolution are needed. Standardising follow-up times and respiratory disease definitions and optimising causal statistical approaches might identify targets for primary prevention of childhood respiratory diseases.

Maternal diet during pregnancy and child neurodevelopment up to age 3.5 years: the nationwide Étude Longitudinale Française depuis l'Enfance (ELFE) birth cohort

BACKGROUND

Dietary guidelines available to pregnant women are made to improve maternal health and fetal development. But their adequacy to sustain offspring neurodevelopment has remained understudied.

OBJECTIVES

We assessed the association between compliance with nutritional guidelines during pregnancy and neurodevelopment in preschool children.

METHODS

The analyses were based on data for 6780 to 11,278 children from the Étude Longitudinale Française depuis l'Enfance (ELFE) study, a nationwide birth cohort. Maternal diet during the last 3 mo of pregnancy was evaluated at delivery by using a validated 125-item FFQ. From this FFQ, food group consumption, a diet quality score (adapted National Health and Nutrition Program Guideline Score), and a nutrient intake score (Probability of Adequate Nutrient intake based Diet quality index) were calculated and dietary patterns were derived by principal component analysis. Child neurodevelopment was reported by parents at 1 and 3.5 y with the Child Development Inventory (CDI-1, CDI-3.5) and at 2 y with the MacArthur-Bates Communicative Development Inventories (MB-2), and assessed by a trained investigator at 3.5 y with the Picture Similarities test (British Ability Scales, PS-3.5). Associations between maternal diet and child neurodevelopment were assessed by multivariable linear regression models on standardized variables.

RESULTS

Higher nutrient intake score was associated with higher neurodevelopmental scores from 1 to 3.5 y (β = 0.04; 95% CI: 0.02, 0.06 for CDI-1; β = 0.03; 95% CI: 0.01, 0.05 for MB-2; and β = 0.03; 95% CI: 0.01, 0.05 for CDI-3.5). Higher fruit and vegetables or fish intake and lower pork-meat products intake were related to higher CDI-3.5 scores (β = 0.03; 95% CI: 0.01, 0.05 for fruit and vegetables; β = 0.03; 95% CI: 0.01, 0.05 for fish; and β = -0.02; 95% CI: -0.04, 0.00 for pork-meat products). A higher score on the processed food pattern was associated with poorer neurodevelopmental score at 1 y (β = -0.05; 95% CI: -0.06, -0.03).

CONCLUSIONS

Higher diet quality during pregnancy was associated with higher parent-reported neurodevelopmental scores in early childhood. The negative association of pork-meat products consumption with early neurodevelopmental scores needs to be further confirmed.

Time of coronary revascularization: methodology of a mediation analysis study

BACKGROUND

The advantage of coronary artery bypass grafting (CABG) over percutaneous coronary intervention (PCI), established in trials, may not be generalizable to populations in which the method of treatment determines the time to treatment. We sought to describe the methodology of a population-based observational study for assessing how changes in time to treatment may affect the comparative effectiveness of these 2 methods of coronary revascularization.

METHODS

We propose a framework of causal mediation analysis to compare the outcomes of choosing CABG over PCI, if patients selected for either method waited the same amount of time had they undergone a PCI. We will include patients who underwent a first-time, nonurgent isolated CABG or single-session PCI for multivessel or left main coronary artery disease from January 2001 to December 2016, in British Columbia. We will use absolute risk difference as a measure of the total effect of choosing CABG over PCI and partition it into the direct effect of the treatment choice and the effect mediated by the treatment-specific timing.

INTERPRETATION

Understanding how time to treatment mediates the relation between method of revascularization and outcomes will have implications for treatment selection, resource allocation and planning benchmarks. Findings on the benefits and risks of performing PCI or CABG within a certain time will guide multidisciplinary teams in determining the appropriate revascularization method for individual patients.

Adverse childhood experiences and prenatal depression in the maternal and development risks from environmental and social stressors pregnancy cohort

The aim of this study was to examine the association between adverse childhood experiences (ACEs) and risk for depression among 480 predominantly low-income Hispanic/Latina women in the Maternal and Development Risks from Environmental and Social Stressors pregnancy cohort. Models were fitted to evaluate associations between ACEs and prenatal probable depression measured by the Center for Epidemiologic Studies-Depression Scale adjusting for recruitment site, age, income, race/ethnicity, marital status and parity. The ACEs Questionnaire parameterised experiences as counts (0-10), categories (0, 1-3 and 4+ ACEs) and domains. Participants had a significantly higher likelihood of prenatal probable depression per unit increase in ACEs count or if they reported 4+ ACEs relative to 0 ACEs. Higher likelihood of probable depression was also associated with higher counts of each ACEs domains: abuse, neglect and household dysfunction. Findings suggest systematic screening for depressive symptoms in those with a history of childhood adversities may be important in prenatal care practice.Impact StatementWhat is already known on this subject? Experiencing depression during pregnancy has been associated with later adverse maternal mental and physical health outcomes. Emerging studies indicate that adverse childhood experiences (ACEs) may maintain or increase the predisposition to prenatal depression.What do the results of this study add? Although prenatal depressive symptoms are prevalent among racial/ethnic minority samples including Hispanic/Latinas, research determining whether the association between ACEs and prenatal depression varies by nativity is scarce. Overall, ACEs were common among Maternal and Developmental Risks from Environmental and Social Stressors (MADRES) participants and were associated with a higher likelihood of probable depression during pregnancy. These patterns did not significantly differ among the foreign-born versus U.S.-born Hispanic/Latina women, although the associations were stronger among U.S.-born Hispanic/Latina women.What are the implications of these findings for clinical practice and/or further research? Research should continue to focus on the effects of ACEs in communities that have been historically excluded in perinatal mental health services such as pregnant women from racial and ethnic minority groups. It may be important for clinicians to routinely screen for mental health during pregnancy as an adverse, psychological environment may impact both women and children. These findings suggest a need for improvement in systematic screening for depressive symptoms in those with a history of childhood adversities.

Socioeconomic position, bronchiolitis and asthma in children: counterfactual disparity measures from a national birth cohort study

BACKGROUND

The debated link between severe respiratory syncytial virus (RSV) infection in early life and asthma has yet to be investigated within a social inequity lens. We estimated the magnitude of socioeconomic disparity in childhood asthma which would remain if no child were admitted to hospital for bronchiolitis, commonly due to RSV, during infancy.

METHODS

The cohort, constructed from national administrative health datasets, comprised 83853 children born in Scotland between 1 January 2007 and 31 June 2008. Scottish Index for Multiple Deprivation (SIMD) was used to capture socioeconomic position. Emergency admissions for bronchiolitis before age 1 year were identified from hospital records. Yearly indicators of asthma/wheeze from ages 2 to 9 years were created using dispensing data and hospital admission records.

RESULTS

Using latent class growth analysis, we identified four trajectories of asthma/wheeze: early-transient (2.2% of the cohort), early-persistent (2.0%), intermediate-onset (1.8%) and no asthma/wheeze (94.0%). The estimated marginal risks of chronic asthma (combining early-persistent and intermediate-onset groups) varied by SIMD, with risk differences for the medium and high deprivation groups, relative to the low deprivation group, of 7.0% (95% confidence interval: 3.7-10.3) and 13.0% (9.6-16.4), respectively. Using counterfactual disparity measures, we estimated that the elimination of bronchiolitis requiring hospital admission could reduce these risk differences by 21.2% (4.9-37.5) and 17.9% (10.4-25.4), respectively.

CONCLUSIONS

The majority of disparity in chronic asthma prevalence by deprivation level remains unexplained. Our paper offers a guide to using causal inference methods to study other plausible pathways to inequities in asthma using complex, linked administrative data.

The Association Between Exposure to COVID-19 and Mental Health Outcomes Among Healthcare Workers

Due to the unprecedented impact of the COVID-19 pandemic on health care systems, there has been great interest in the mental wellbeing of healthcare workers. While most studies investigated mental health outcomes among frontline vs. non-frontline healthcare workers, little is known about the impact of various work-related variables. The present study aimed to examine the association between work-related [i.e., having contact with COVID-19 patients, being redeployed due to the pandemic and availability of sufficient personal protective equipment (PPE)] and subjective (i.e., worries about getting infected or infecting others) exposures and self-reported mental health outcomes (i.e., psychological distress, depressive symptoms, and posttraumatic stress symptoms). Between February and May 2021, 994 healthcare workers employed at a variety of healthcare settings in the Netherlands filled out an online survey as part of the COVID-19 HEalth caRe wOrkErS (HEROES) study. Mental health outcomes were measured using the General Health Questionnaire-12, the Patient Health Questionnaire-9, and the Primary Care PTSD Screen for DSM-5. Approximately 13% reported depressive symptoms, 37% experienced psychological distress, and 20% reported posttraumatic stress symptoms. Multilevel linear models consisted of three levels: individual (work-related and subjective exposures), healthcare center (aggregated redeployment and availability of sufficient PPE), and regional (cumulative COVID-19 infection and death rates). Worries about infection were associated with all three mental health outcomes, whereas insufficient PPE was associated with psychological distress and depressive symptoms. There were no differences in outcomes between healthcare centers or provinces with different COVID-19 infection and death rates. Our findings highlight the importance of adequate PPE provision and the subjective experience of the COVID-19 pandemic. These factors should be part of interventions aimed at mitigating adverse mental health outcomes among healthcare workers during the COVID-19 pandemic.

Reflection on modern methods: constructing directed acyclic graphs (DAGs) with domain experts for health services research

Directed acyclic graphs (DAGs) are a useful tool to represent, in a graphical format, researchers’ assumptions about the causal structure among variables while providing a rationale for the choice of confounding variables to adjust for. With origins in the field of probabilistic graphical modelling, DAGs are yet to be widely adopted in applied health research, where causal assumptions are frequently made for the purpose of evaluating health services initiatives. In this context, there is still limited practical guidance on how to construct and use DAGs. Some progress has recently been made in terms of building DAGs based on studies from the literature, but an area that has received less attention is how to create DAGs from information provided by domain experts, an approach of particular importance when there is limited published information about the intervention under study. This approach offers the opportunity for findings to be more robust and relevant to patients, carers and the public, and more likely to inform policy and clinical practice. This article draws lessons from a stakeholder workshop involving patients, health care professionals, researchers, commissioners and representatives from industry, whose objective was to draw DAGs for a complex intervention—online consultation, i.e. written exchange between the patient and health care professional using an online system—in the context of the English National Health Service. We provide some initial, practical guidance to those interested in engaging with domain experts to develop DAGs.

Mediators of socioeconomic inequalities in preterm birth: a systematic review

BACKGROUND

Rates of preterm birth are substantial with significant inequalities. Understanding the role of risk factors on the pathway from maternal socioeconomic status (SES) to preterm birth can help inform interventions and policy. This study therefore aimed to identify mediators of the relationship between maternal SES and preterm birth, assess the strength of evidence, and evaluate the quality of methods used to assess mediation.

METHODS

Using Scopus, Medline OVID, "Medline In Process & Other Non-Indexed Citation", PsycINFO, and Social Science Citation Index (via Web of Science), search terms combined variations on mediation, socioeconomic status, and preterm birth. Citation and advanced Google searches supplemented this. Inclusion criteria guided screening and selection of observational studies Jan-2000 to July-2020. The metric extracted was the proportion of socioeconomic inequality in preterm birth explained by each mediator (e.g. 'proportion eliminated'). Included studies were narratively synthesised.

RESULTS

Of 22 studies included, over one-half used cohort design. Most studies had potential measurement bias for mediators, and only two studies fully adjusted for key confounders. Eighteen studies found significant socioeconomic inequalities in preterm birth. Studies assessed six groups of potential mediators: maternal smoking; maternal mental health; maternal physical health (including body mass index (BMI)); maternal lifestyle (including alcohol consumption); healthcare; and working and environmental conditions. There was high confidence of smoking during pregnancy (most frequently examined mediator) and maternal physical health mediating inequalities in preterm birth. Significant residual inequalities frequently remained. Difference-of-coefficients between models was the most common mediation analysis approach, only six studies assessed exposure-mediator interaction, and only two considered causal assumptions.

CONCLUSIONS

The substantial socioeconomic inequalities in preterm birth are only partly explained by six groups of mediators that have been studied, particularly maternal smoking in pregnancy. There is, however, a large residual direct effect of SES evident in most studies. Despite the mediation analysis approaches used limiting our ability to make causal inference, these findings highlight potential ways of intervening to reduce such inequalities. A focus on modifiable socioeconomic determinants, such as reducing poverty and educational inequality, is probably necessary to address inequalities in preterm birth, alongside action on mediating pathways.

Associations between Smoking and Alcohol and Follicular Lymphoma Incidence and Survival: A Family-Based Case-Control Study in Australia

The association between smoking and alcohol consumption and follicular lymphoma (FL) incidence and clinical outcome is uncertain. We conducted a population-based family case-control study (709 cases: 490 controls) in Australia. We assessed lifetime history of smoking and recent alcohol consumption and followed-up cases (median = 83 months). We examined associations with FL risk using unconditional logistic regression and with all-cause and FL-specific mortality of cases using Cox regression. FL risk was associated with ever smoking (OR = 1.38, 95%CI = 1.08−1.74), former smoking (OR = 1.36, 95%CI = 1.05−1.77), smoking initiation before age 17 (OR = 1.47, 95%CI = 1.06−2.05), the highest categories of cigarettes smoked per day (OR = 1.44, 95%CI = 1.04−2.01), smoking duration (OR = 1.53, 95%CI = 1.07−2.18) and pack-years (OR = 1.56, 95%CI = 1.10−2.22). For never smokers, FL risk increased for those exposed indoors to >2 smokers during childhood (OR = 1.84, 95%CI = 1.11−3.04). For cases, current smoking and the highest categories of smoking duration and lifetime cigarette exposure were associated with elevated all-cause mortality. The hazard ratio for current smoking and FL-specific mortality was 2.97 (95%CI = 0.91−9.72). We found no association between recent alcohol consumption and FL risk, all-cause or FL-specific mortality. Our study showed consistent evidence of an association between smoking and increased FL risk and possibly also FL-specific mortality. Strengthening anti-smoking policies and interventions may reduce the population burden of FL.