Attributable fraction for multiple risk factors: Methods, interpretations, and examples

Post-traumatic stress, depression, and anxiety during the 2021 Myanmar conflict: a nationwide population-based survey

Background

The UN warns that Myanmar faces the 'triple crises' of mass conflict, uncontrolled COVID-19, and economic collapse. Therefore, we aimed to assess the population mental health burden, healthcare needs, and the associated risk factors in Myanmar.

Methods

We established a nationwide random sample and recruited 1038 adults via random digit dialling from July 3-Aug 9, 2021, during the ongoing conflict since Feb 1, 2021, and surge in SARS-CoV-2 infections. Probable post-traumatic stress disorder (PTSD) was assessed using the PTSD Checklist-Civilian Version. Probable depression and anxiety were assessed using the Patient Health Questionnaire-2 and the Generalized Anxiety Disorder-2. We calculated population attributable fractions for probable mental disorders using multivariable logistic regression models. Based on the mental health burden and healthcare-seeking patterns, we projected the need for mental health services.

Findings

During the 'triple crises', a third of adults in Myanmar (34.9%, 95% CI 32.0-37.7) reported a probable mental disorder. Prevalence of probable PTSD, depression, and anxiety were 8.1% (6.6-9.7), 14.3% (12.0-16.6), and 22.2% (19.7-24.7), respectively. We estimated that up to 79.9% (43.8-97.9) of probable PTSD was attributable to political stress. This corresponds to 2.1 million (1.1-3.2 million) fewer adults with probable PTSD if political stress was removed from the population. The mental health burden could translate into roughly 5.9 million adults seeking mental health services.

Interpretation

The mental health burden in Myanmar is substantial, and population mental health might only be restored when the three crises have ended. An accelerated peace process is critical to protecting Myanmar's population mental health.

Funding

This research was supported the Research Grants Council of the Hong Kong Special Administrative Region, China (Project No. HKU 17606122) and the Michele Tansella Award.

Interaction and joint association of gestational diabetes mellitus and subsequent weight gain rate on macrosomia

BACKGROUND & AIMS

Gestational diabetes mellitus (GDM) and gestational weight gain are two crucial modifiable nutritional factors during pregnancy in preventing macrosomia, warranting appropriate management of both glycemic levels and weight gain to prevent macrosomia, particularly in individuals with GDM. Unfortunately, current general weight targets appear not to apply to individuals with GDM, suggesting that weight gain, specifically following an oral glucose tolerance test (OGTT), may affect risk of macrosomia dependent on GDM status. Therefore, this study aims to evaluate the interaction and joint association of GDM and post-OGTT weight gain rate (PWGR) in relation to macrosomia.

METHODS

This was a population-based cohort study of 59,421singleton pregnant women in South China during 2017-2020. Among them, 9856 were diagnosed with GDM while 49,565 did not have the condition. All participants underwent an OGTT between 20 and 28 weeks of pregnancy, typically occurring between 24 and 28 weeks. PWGR was defined as the average rate of change in maternal weight with gestational weeks following OGTT, which was estimated using a repeated linear mixed effects model including a random intercept and slope for each individual. The relative risk (RR) of macrosomia associated with GDM and PWGR was estimated using a multivariate generalized linear model.

RESULTS

There was a significant interaction between GDM and PWGR in increasing the risk of macrosomia. The combination of GDM and a 1-SD increase in PWGR was associated with a 2.26-fold higher risk of macrosomia (95% CI 1.92 to 2.65), with the interaction of these two factors contributing to 58.0% (95% CI 31.4%-84.7%) of this association. Moreover, we observed a significant heterogeneity in susceptibility to macrosomia due to increased PWGR between GDM and non-GDM populations, with the highest PWGR quartile having respective RRs of 2.27 (95% CI 1.62 to 3.18) and 1.41 (95% CI 1.18 to 1.69) compared to the lowest quartile category, which was corresponded to 55.9% (95% CI 38.3%-68.6%) and 29.1% (95% CI 15.3%-40.8%) preventable proportions of macrosomia cases in these populations.

CONCLUSIONS

GDM and PWGR had a synergistic effect in increasing the risk of macrosomia. Furthermore, individuals with GDM exhibited a heightened susceptibility to macrosomia due to elevated PWGR. These findings emphasize the importance of appropriate weight interventions during late pregnancy and suggest the need for different weight targets between these two populations, with a stricter PWGR potentially being more effective for the GDM population.

Have We Been Underestimating Modifiable Dementia Risk? An Alternative Approach for Calculating the Combined Population Attributable Fraction for Modifiable Dementia Risk Factors

Estimating the fraction of dementia cases in a population attributable to a risk factor or combination of risk factors (the population attributable fraction (PAF)) informs the design and choice of dementia risk-reduction activities. It is directly relevant to dementia prevention policy and practice. Current methods employed widely in the dementia literature to combine PAFs for multiple dementia risk factors assume a multiplicative relationship between factors and rely on subjective criteria to develop weightings for risk factors. In this paper we present an alternative approach to calculating the PAF based on sums of individual risk. It incorporates individual risk factor interrelationships and enables a range of assumptions about the way in which multiple risk factors will combine to affect dementia risk. Applying this method to global data demonstrates that the previous estimate of 40% is potentially too conservative an estimate of modifiable dementia risk and would necessitate subadditive interaction between risk factors. We calculate a plausible conservative estimate of 55.7% (95% confidence interval: 55.2, 56.1) based on additive risk factor interaction.

COVID-19 Vaccination Willingness and Reasons for Vaccine Refusal

Importance

Hong Kong was held as an exemplar for pandemic response until it recorded the world's highest daily COVID-19 mortality, which was likely due to vaccine refusal. To prevent this high mortality in future pandemics, information on underlying reasons for vaccine refusal is necessary.

Objectives

To track the evolution of COVID-19 vaccination willingness and uptake from before vaccine rollout to mass vaccination, to examine factors associated with COVID-19 vaccine refusal and compare with data from Singapore, and to assess the population attributable fraction for vaccine refusal.

Design, Setting, and Participants

This cohort study used data from randomly sampled participants from 14 waves of population-based studies in Hong Kong (February 2020 to May 2022) and 2 waves of population-based studies in Singapore (May 2020 to June 2021 and October 2021 to January 2022), and a population-wide registry of COVID-19 vaccination appointments. Data were analyzed from February 23, 2021, to May 30, 2022.

Exposures

Trust in COVID-19 vaccine information sources (ie, health authorities, physicians, traditional media, and social media); COVID-19 vaccine confidence on effectiveness, safety, and importance; COVID-19 vaccine misconceptions on safety and high-risk groups; political views; and COVID-19 policies (ie, workplace vaccine mandates and vaccine pass).

Main Outcomes and Measures

Primary outcomes were the weighted prevalence of COVID-19 vaccination willingness over the pandemic, adjusted incidence rate ratios, and population attributable fractions of COVID-19 vaccine refusal. A secondary outcome was change in daily COVID-19 vaccination appointments.

Results

The study included 28 007 interviews from 20 waves of longitudinal data, with 1114 participants in the most recent wave (median [range] age, 54.2 years [20-92] years; 571 [51.3%] female). Four factors-mistrust in health authorities, low vaccine confidence, vaccine misconceptions, and political views-could jointly account for 82.2% (95% CI, 62.3%-100.0%) of vaccine refusal in adults aged 18 to 59 years and 69.3% (95% CI, 47.2%-91.4%) of vaccine refusal in adults aged 60 years and older. Workplace vaccine mandates were associated with 62.2% (95% CI, 9.9%-139.2%) increases in daily COVID-19 vaccination appointments, and the Hong Kong vaccine pass was associated with 124.8% (95% CI, 65.9%-204.6%) increases in daily COVID-19 vaccination appointments.

Conclusions and Relevance

These findings suggest that trust in health authorities was fundamental to overcoming vaccine hesitancy. As such, engendering trust in health care professionals, experts, and public health agencies should be incorporated into pandemic preparedness and response.

Cancers attributable to infectious agents in Italy

OBJECTIVES

To provide an evidence-based, comprehensive assessment of the current burden of infection-related cancers in Italy.

METHODS

We calculated the proportion of cancers attributable to infectious agents (Helicobacter pylori [Hp]; hepatitis B virus [HBV] and hepatitis C virus [HCV]; human papillomavirus [HPV]; human herpesvirus-8 [HHV8]; Epstein-Barr virus [EBV]; and human immunodeficiency virus [HIV]) to estimate the burden of infection-related cancer incidence (2020) and mortality (2017). Data on the prevalence of infections were derived from cross-sectional surveys of the Italian population, and relative risks from meta-analyses and large-scale studies. Attributable fractions were calculated based on the counterfactual scenario of a lack of infection.

RESULTS

We estimated that 7.6% of total cancer deaths in 2017 were attributable to infections, with a higher proportion in men (8.1%) than in women (6.9%). The corresponding figures for incident cases were 6.5%, 6.9% and 6.1%. Hp was the first cause of infection-related cancer deaths (3.3% of the total), followed by HCV (1.8%), HIV (1.1%), HBV (0.9%), HPV, EBV and HHV8 (each ≤0.7%). Regarding incidence, 2.4% of the new cancer cases were due to Hp, 1.3% due to HCV, 1.2% due to HIV, 1.0% due to HPV, 0.6% due to HBV and <0.5% due to EBV and HHV8.

CONCLUSIONS

Our estimate of 7.6% of cancer deaths and 6.9% of incident cases that were attributable to infections in Italy is higher than those estimated in other developed countries. Hp is the major cause of infection-related cancer in Italy. Prevention, screening and treatment policies are needed to control these cancers, which are largely avoidable.

Race‐related population attributable fraction of preventable risk factors of dementia: A Latino population‐based study

Background

Risk factors for dementia have distinct frequency and impact in relation to race. Our aim was to identify differences in modifiable risk factors of dementia related to races and estimate their population attributable fraction (PAF).

Methods

An epidemiological cohort was used to estimate the prevalence of 10 modifiable risk factors for dementia among five races—White, Black, Brown, Asian, and Indigenous. Sample weighting was used to estimate the prevalence and PAF of each risk factor in each race.

Results

A total of 9070 individuals were included. Overall adjusted PAF was the lowest in Indigenous (38.9%), and Asian individuals (41.2%). Race‐related prevalence of individual risk factors was widely variable in our population, but hearing loss was the most important contributor to the overall PAF in all races.

Conclusions

Public policies aiming to reduce preventable risk factors for dementia should take into consideration the race of the target populations.

HIGHLIGHTS

Preventable risk factors for dementia vary according to race.

Hearing loss presented the highest prevalence among all races studied.

Indigenous and Asian individuals presented the lowest population attributable fractions.

Black and Brown individuals were more vulnerable to social determinants.

Pathway-specific population attributable fractions

INTRODUCTION

A population attributable fraction represents the relative change in disease prevalence that one might expect if a particular exposure was absent from the population. Often, one might be interested in what percentage of this effect acts through particular pathways. For instance, the effect of a sedentary lifestyle on stroke risk may be mediated by blood pressure, body mass index and several other intermediate risk factors.

METHODS

We define a new metric, the pathway-specific population attributable fraction (PS-PAF), for mediating pathways of interest. PS-PAFs can be informally defined as the relative change in disease prevalence from an intervention that shifts the distribution of the mediator to its expected distribution if the risk factor were eliminated, and sometimes more simply as the relative change in disease prevalence if the mediating pathway were disabled. A potential outcomes framework is used for formal definitions and associated estimands are derived via relevant identifiability conditions. Computationally efficient estimators for PS-PAFs are derived based on these identifiability conditions.

RESULTS

Calculations are demonstrated using INTERSTROKE-an international case-control study designed to quantify disease burden attributable to a number of known causal risk factors. The applied results suggest that mediating pathways from physical activity through blood pressure, blood lipids and body size explain comparable proportions of stroke disease burden, but a large proportion of the disease burden due to physical inactivity may be explained by alternative pathways.

CONCLUSION

PS-PAFs measure disease burden attributable to differing mediating pathways and can generate insights into the dominant mechanisms by which a risk factor affects disease at a population level.

Simulation study on the validity of the average risk approach in estimating population attributable fractions for continuous exposures

BACKGROUND

The population attributable fraction (PAF) is an important metric for estimating disease burden associated with causal risk factors. In an International Agency for Research on Cancer working group report, an approach was introduced to estimate the PAF using the average of a continuous exposure and the incremental relative risk (RR) per unit. This 'average risk' approach has been subsequently applied in several studies conducted worldwide. However, no investigation of the validity of this method has been done.

OBJECTIVE

To examine the validity and the potential magnitude of bias of the average risk approach.

METHODS

We established analytically that the direction of the bias is determined by the shape of the RR function. We then used simulation models based on a variety of risk exposure distributions and a range of RR per unit. We estimated the unbiased PAF from integrating the exposure distribution and RR, and the PAF using the average risk approach. We examined the absolute and relative bias as the direct and relative difference in PAF estimated from the two approaches. We also examined the bias of the average risk approach using real-world data from the Canadian Population Attributable Risk of Cancer study.

RESULTS

The average risk approach involves bias, which is underestimation or overestimation with a convex or concave RR function (a risk profile that increases more/less rapidly at higher levels of exposure). The magnitude of the bias is affected by the exposure distribution as well as the value of RR. This approach is approximately valid when the RR per unit is small or the RR function is approximately linear. The absolute and relative bias can both be large when RR is not small and the exposure distribution is skewed.

CONCLUSIONS

We recommend that caution be taken when using the average risk approach to estimate PAF.

Alcohol drinking and head and neck cancer risk: the joint effect of intensity and duration

BACKGROUND

Alcohol is a well-established risk factor for head and neck cancer (HNC). This study aims to explore the effect of alcohol intensity and duration, as joint continuous exposures, on HNC risk.

METHODS

Data from 26 case-control studies in the INHANCE Consortium were used, including never and current drinkers who drunk ≤10 drinks/day for ≤54 years (24234 controls, 4085 oral cavity, 3359 oropharyngeal, 983 hypopharyngeal and 3340 laryngeal cancers). The dose-response relationship between the risk and the joint exposure to drinking intensity and duration was investigated through bivariate regression spline models, adjusting for potential confounders, including tobacco smoking.

RESULTS

For all subsites, cancer risk steeply increased with increasing drinks/day, with no appreciable threshold effect at lower intensities. For each intensity level, the risk of oral cavity, hypopharyngeal and laryngeal cancers did not vary according to years of drinking, suggesting no effect of duration. For oropharyngeal cancer, the risk increased with durations up to 28 years, flattening thereafter. The risk peaked at the higher levels of intensity and duration for all subsites (odds ratio = 7.95 for oral cavity, 12.86 for oropharynx, 24.96 for hypopharynx and 6.60 for larynx).

CONCLUSIONS

Present results further encourage the reduction of alcohol intensity to mitigate HNC risk.