To Adjust or Not to Adjust: The Role of Different Covariates in Cardiovascular Observational Studies

Causal diagrams for disease latency bias

BACKGROUND

Disease latency is defined as the time from disease initiation to disease diagnosis. Disease latency bias (DLB) can arise in epidemiological studies that examine latent outcomes, since the exact timing of the disease inception is unknown and might occur before exposure initiation, potentially leading to bias. Although DLB can affect epidemiological studies that examine different types of chronic disease (e.g. Alzheimer's disease, cancer etc), the manner by which DLB can introduce bias into these studies has not been previously elucidated. Information on the specific types of bias, and their structure, that can arise secondary to DLB is critical for researchers, to enable better understanding and control for DLB.

DEVELOPMENT

Here we describe four scenarios by which DLB can introduce bias (through different structures) into epidemiological studies that address latent outcomes, using directed acyclic graphs (DAGs). We also discuss potential strategies to better understand, examine and control for DLB in these studies.

APPLICATION

Using causal diagrams, we show that disease latency bias can affect results of epidemiological studies through: (i) unmeasured confounding; (ii) reverse causality; (iii) selection bias; (iv) bias through a mediator.

CONCLUSION

Disease latency bias is an important bias that can affect a number of epidemiological studies that address latent outcomes. Causal diagrams can assist researchers better identify and control for this bias.

Adherence to a Mediterranean-style diet and severity of menopausal symptoms in perimenopausal and menopausal women from Australia: a cross-sectional analysis

PURPOSE

To explore the independent associations between adherence to a Mediterranean-style diet and severity of menopausal symptoms in perimenopausal and menopausal women living in Australia.

METHODS

Dietary adherence was assessed using the Mediterranean Diet Adherence Screener (MEDAS), the Menopause Rating Scale (MRS) was used to assess the severity of menopausal symptoms, and the 36-item short form survey instrument (SF-36) was used to assess health-related quality of life (HRQoL).

RESULTS

A total of n = 207 participants (50.7 ± 4.3 years; BMI: 28.0 ± 7.4 kg/m2) were included in the final analyses. Participants reported low-moderate adherence to a Mediterranean-style diet (5.2 ± 1.8; range: 1-11). Adherence was not associated with severity of menopausal symptoms. However, low consumption of sugar-sweetened beverages was inversely associated with joint and muscle complaints, independent of all covariates (β = -0.149; CI: -0.118, -0.022; P = 0.042). Adherence to a Mediterranean-style diet was positively associated with the physical function subscale of HRQoL (β = 0.173, CI: 0.001, 0.029; P = 0.031) and a low intake of red and processed meat was positively associated with the general health subscale (β = 0.296, CI: 0.005, 0.014; P = < 0.001).

CONCLUSION

Diet quality may be related to severity of menopausal symptoms and HRQoL in perimenopausal and menopausal women. However, exploration of these findings using longitudinal analyses and robust clinical trials are needed to better elucidate these findings.

The Oral Health Statistics Guidelines for Reporting Observational Studies and Clinical Trials in Oral Health Research: Explanation and Elaboration

Adequate and transparent reporting is necessary for critically appraising research. Yet, evidence suggests that the design, conduct, analysis, interpretation, and reporting of oral health research could be greatly improved. Accordingly, the Task Force on Design and Analysis in Oral Health Research-statisticians and trialists from academia and industry-empaneled a group of authors to develop methodological and statistical reporting guidelines identifying the minimum information needed to document and evaluate observational studies and clinical trials in oral health: the Oral Health Statistics Guidelines. Drafts were circulated to the editors of 85 oral health journals and to task force members and sponsors and discussed at a December 2020 workshop attended by 49 researchers. The final version was subsequently approved by the task force in September 2021, submitted for journal review in 2022, and revised in 2023. The checklist consists of 48 guidelines: 5 for introductory information, 17 for methods, 13 for statistical analysis, 6 for results, and 7 for interpretation; 7 are specific to clinical trials. Each of these guidelines identifies relevant information, explains its importance, and often describes best practices. The checklist was published in multiple journals. The article was published simultaneously in Journal of Dental Research Clinical and Translational Research, the Journal of the American Dental Association, and the Journal of Oral and Maxillofacial Surgery. Completed checklists should accompany manuscripts submitted for publication to these and other oral health journals to help authors, journal editors, and reviewers verify that the manuscript provides the information necessary to adequately document and evaluate the research.

The OHStat Guidelines for Reporting Observational Studies and Clinical Trials in Oral Health Research: explanation and elaboration

Adequate and transparent reporting is necessary for critically appraising research. Yet, evidence suggests that the design, conduct, analysis, interpretation, and reporting of oral health research could be greatly improved. Accordingly, the Task Force on Design and Analysis in Oral Health Research-statisticians and trialists from academia and industry-empaneled a group of authors to develop methodological and statistical reporting guidelines identifying the minimum information needed to document and evaluate observational studies and clinical trials in oral health: the OHstat Guidelines. Drafts were circulated to the editors of 85 oral health journals and to Task Force members and sponsors and discussed at a December 2020 workshop attended by 49 researchers. The final version was subsequently approved by the Task Force in September 2021, submitted for journal review in 2022, and revised in 2023. The checklist consists of 48 guidelines: 5 for introductory information, 17 for methods, 13 for statistical analysis, 6 for results, and 7 for interpretation; 7 are specific to clinical trials. Each of these guidelines identifies relevant information, explains its importance, and often describes best practices. The checklist was published in multiple journals. The article was published simultaneously in JDR Clinical and Translational Research, the Journal of the American Dental Association, and the Journal of Oral and Maxillofacial Surgery. Completed checklists should accompany manuscripts submitted for publication to these and other oral health journals to help authors, journal editors, and reviewers verify that the manuscript provides the information necessary to adequately document and evaluate the research.

The OHStat Guidelines for Reporting Observational Studies and Clinical Trials in Oral Health Research: Explanation and Elaboration

Adequate and transparent reporting is necessary for critically appraising research. Yet, evidence suggests that the design, conduct, analysis, interpretation, and reporting of oral health research could be greatly improved. Accordingly, the Task Force on Design and Analysis in Oral Health Research-statisticians and trialists from academia and industry-empaneled a group of authors to develop methodological and statistical reporting guidelines identifying the minimum information needed to document and evaluate observational studies and clinical trials in oral health: the OHstat Guidelines. Drafts were circulated to the editors of 85 oral health journals and to Task Force members and sponsors and discussed at a December 2020 workshop attended by 49 researchers. The final version was subsequently approved by the Task Force in September 2021, submitted for journal review in 2022, and revised in 2023. The checklist consists of 48 guidelines: 5 for introductory information, 17 for methods, 13 for statistical analysis, 6 for results, and 7 for interpretation; 7 are specific to clinical trials. Each of these guidelines identifies relevant information, explains its importance, and often describes best practices. The checklist was published in multiple journals. The article was published simultaneously in JDR Clinical and Translational Research, the Journal of the American Dental Association, and the Journal of Oral and Maxillofacial Surgery. Completed checklists should accompany manuscripts submitted for publication to these and other oral health journals to help authors, journal editors, and reviewers verify that the manuscript provides the information necessary to adequately document and evaluate the research.

Transactional Sex, HIV, and Bacterial STIs Among U.S. Men Who have Sex with Men

INTRODUCTION

Men who have sex with men (MSM) and are engaged in transactional sex (MSM-TS) experience complex social and structural vulnerabilities that increase their HIV risk. This study aimed to estimate the prevalence of TS and associations between TS and sexually transmitted infection (STI) outcomes among cisgender MSM in the U.S.

METHODS

Using 2017-2021 data from an online survey of U.S. MSM, characteristics of MSM-TS were summarized, and adjusted prevalence ratios (aPRs) calculated for the associations between past-year TS and bacterial STI diagnosis, HIV status, and either antiretroviral or pre-exposure prophylaxis use. Analyses were conducted in 2023.

RESULTS

TS prevalence was 3.7% (n=1,848/49,539). Compared to other MSM, MSM-TS more commonly reported homelessness, being uninsured, condomless anal sex with partners of any HIV status and condomless anal sex with serodifferent partners, and illicit drug use. TS was associated with increased HIV (aPR 1.44, 95% CI 1.25-1.66) and bacterial STI prevalence (aPR 2.40, 95% CI=2.09-2.52) and lower antiretroviral therapy use (among MSM living with HIV; PR 0.92, 95% CI=0.87-0.97).

CONCLUSIONS

Structural and behavioral risks converged among U.S. MSM engaging in TS leading to greater HIV and bacterial STI prevalence in this group. HIV interventions for U.S. MSM-TS should address individual as well as structural risks, including poverty and housing instability.

Comparison of outcomes between off-pump and on-pump coronary artery bypass graft surgery using collaborative targeted maximum likelihood estimation

There are some discrepancies about the superiority of the off-pump coronary artery bypass grafting (CABG) surgery over the conventional cardiopulmonary bypass (on-pump). The aim of this study was estimating risk ratio of mortality in the off-pump coronary bypass compared with the on-pump using a causal model known as collaborative targeted maximum likelihood estimation (C-TMLE). The data of the Tehran Heart Cohort study from 2007 to 2020 was used. A collaborative targeted maximum likelihood estimation and targeted maximum likelihood estimation, and propensity score (PS) adjustment methods were used to estimate causal risk ratio adjusting for the minimum sufficient set of confounders, and the results were compared. Among 24,883 participants (73.6% male), 5566 patients died during an average of 8.2 years of follow-up. The risk ratio estimates (95% confidence intervals) by unadjusted log-binomial regression model, PS adjustment, TMLE, and C-TMLE methods were 0.86 (0.78-0.95), 0.88 (0.80-0.97), 0.88 (0.80-0.97), and 0.87(0.85-0.89), respectively. This study provides evidence for a protective effect of off-pump surgery on mortality risk for up to 8 years in diabetic and non-diabetic patients.

Intraoperative and immediate postoperative transfusion: Clinical-hematological profile of transfunded patients in a university hospital

INTRODUCTION

The transfusion practice by surgery blood reserve, varied among services, must be performed through the rational and restrictive use of blood components because it is a scarce and expensive resource for health care services.

OBJECTIVE

Analyze the use of blood products for surgery blood reserve by means of the study of the clinical-hematological profile of patients submitted to intraoperative and immediate postoperative transfusions.

METHODS

This was an observational, cross-sectional, and retrospective study, conducted by collecting biological, operational, and laboratory variables, involving 680 patients at a university hospital who had elective surgery with surgery blood reserve request sent during the period from October 2021 to October 2022.

RESULTS

The overall transfusion rate was 25.44%, and the mean preoperative hemoglobin level of transfused patients was 9.74 ± 2.50 g/dL, with the mean number of transfusions packed red blood cell units was 1.58 ± 0.77. Patients with higher preoperative hemoglobin levels were less likely to have transfusion (p < 0.001) and patients who had surgical oncologic were more likely to require transfusion (p = 0.048). The transfusion rate of packed red blood cells and platelets concentrates, compared to what was requested, was 15.86% and 5.82%.

CONCLUSION

There is a tendency of transfusions to follow restrictive models, with higher transfusion probability in surgical oncologic. Furthermore, there should be more a conscise use of the surgery blood reserves request.

Opt-in versus universal codeine provision for medical abortion up to 10 weeks of gestation at British Pregnancy Advisory Service: a cross-sectional evaluation

OBJECTIVE

To assess patient experiences of pain management during medical abortion up to 10 weeks' gestation with opt-in versus universal codeine provision.

METHODS

We invited patients who underwent medical abortion up to 10 weeks of gestation to participate in an online, anonymous, English-language survey from November 2021 to March 2022. We performed ordinal regression analyses to compare satisfaction with pain management (5-point Likert scale) and maximum abortion pain score (11-point numerical rating scale) in the opt-in versus universal codeine provision groups.

RESULTS

Of 11 906 patients invited to participate, 1625 (13.6%) completed the survey. Participants reported a mean maximum pain score of 6.8±2.2. A total of 1149 participants (70.7%) reported using codeine for pain management during their abortion. Participants in the opt-in codeine provision group were significantly more likely to be satisfied with their pain management than those in the universal group (aOR 1.48, 95% CI 1.12 to 1.96, p<0.01). Maximum abortion pain scores were lower on average among the opt-in codeine provision group (OR 0.80, 95% CI 0.66 to 0.96, p=0.02); however, this association was not statistically significant in the model adjusted for covariates (aOR 0.85, 95% CI 0.70 to 1.03, p=0.09).

CONCLUSION

Our findings suggest that patients have a better experience with pain management during medical abortion when able to opt-in to codeine provision following counselling versus receiving this medication routinely.

Transactional sex among adults accessing sexual health services in Alabama, 2008-2022: Prevalence, associated risk factors, and associations with HIV, HCV, and STI diagnosis

BACKGROUND

The U.S. Deep South bears a disproportionate burden of HIV and other STIs. Transactional sex may influence these epidemics, but few studies have estimated its prevalence or correlates in the Deep South.

METHODS

We estimated the history of transactional sex among adults accessing an Alabama AIDS Service Organization from 2008-2022, using chi-square tests to examine its sociodemographic and behavioral correlates. We used modified Poisson regression with cluster-robust standard errors to estimate adjusted prevalence ratios (aPR) and 95 % confidence intervals (CI) for the associations between transactional sex and new HIV, hepatitis C (HCV), and STI diagnoses.

RESULTS

Transactional sex was reported at 944/20,013 visits (4.7 %) and associated with older age, being a cisgender woman or gender minority, identifying as white, diverse drug use, and sharing of drug equipment. Compared to others, clients reporting transactional sex had increased prevalence of syphilis (apR 3.60, 95 % CI 1.16-11.19) and HCV (aPR 1.53, 95 % CI 1.24-1.88).

CONCLUSION

Using 14 years of community-based data, this study is the first to estimate the relationship between transactional sex and HIV, HCV, and STIs in Alabama and highlights the need address STI burden and diverse drug use among people who transact sex in the Deep South.

Validity and reliability of the persian version of the world health organization quality of life disabilities module

This study aimed to assess the validity and reliability of the world health organization quality of life questionnaire for people with intellectual disability (WHOQOL-DIS-ID). This was a cross-sectional study of 118 adults with intellectual disability. Internal consistency and temporal reliability were evaluated using Cronbach's alpha and intraclass correlation coefficient (ICC), respectively. Construct validity of the structure was assessed using confirmatory factor analysis. Multiple linear regression analysis was performed to determine the factors associated with the quality of life. Cronbach's alpha for all, but not for discrimination area, as well as ICC for all questions except for 23 and 6, were higher than 0.7. The variables such as periodic check-up, number of friends, entertainment outside the home, parental separation, physical activity, unmet needs score, caregiver's mental health status, and available facilities were the predictors of QOL. The Persian version of the WHOQOL-DIS-ID shows acceptable validity and reliability.

Multiple Sclerosis Risk Among Anti-tumor Necrosis Factor Alpha Users: A Methodological Review of Observational Studies Based on Real-world Data

Epidemiologic studies on the risk of multiple sclerosis (MS) or demyelinating events associated with anti-tumor necrosis factor alpha (TNFα) use among patients with rheumatic diseases or inflammatory bowel diseases have shown conflicting results. Causal directed acyclic graphs (cDAGs) are useful tools for understanding the differing results and identifying the structure of potential contributing biases. Most of the available literature on cDAGs uses language that might be unfamiliar to clinicians. This article demonstrates how cDAGs can be used to determine whether there is a confounder, a mediator or collider-stratification bias and when to adjust for them appropriately. We also use a case study to show how to control for potential biases by drawing a cDAG depicting anti-TNFα use and its potential to contribute to MS onset. Finally, we describe potential biases that might have led to contradictory results in previous studies that examined the effect of anti-TNFα and MS, including confounding, confounding by contraindication, and bias due to measurement error. Clinicians and researchers should be cognizant of confounding, confounding by contraindication, and bias due to measurement error when reviewing future studies on the risk of MS or demyelinating events associated with anti-TNFα use. cDAGs are a useful tool for selecting variables and identifying the structure of different biases that can affect the validity of observational studies.

Effect of Lipid-Lowering Drugs on Renal and Cardiovascular Outcomes in Patients with Chronic Kidney Disease and Dyslipidemia: A Retrospective Cohort Study

The effects of lipid-lowering drugs (LLDs) on cardiovascular and renal outcomes in patients with advanced chronic kidney disease (CKD) and dyslipidemia are not completely understood. We conducted a retrospective cohort study to evaluate the effect of LLDs on end-stage kidney disease (ESKD), major adverse cardiovascular events (MACEs), and mortality in adult patients with CKD stage 3b, 4, or 5, and dyslipidemia. Participants were recruited between January 1, 2008, and December 31, 2018, and classified as LLD or non-LLD users; the final follow-up date was December 31, 2020. The primary outcome was time to ESKD or death due to renal failure. Sub-distribution hazard regression models adjusted for multivariables, including time-varying lipid profile covariates, were used for the analysis. Among the 6,740 participants, 4,280 patients with CKD and dyslipidemia, including 872 using LLDs and 3,408 not using LLDs, completed the primary analysis. The multivariable analyses showed that LLD users had a significantly lower risk of time to the composite renal outcome (adjusted hazard ratio [aHR], 0.76, 95% confidence interval [CI], 0.65-0.89), and MACE incidence (aHR, 0.75, 95% CI, 0.62-0.93) than did non-LLD users. After adjusting for time-varying covariates of the lipid profile, there was a significant difference in the composite renal outcome (aHR, 0.78, 95% CI, 0.65-0.93) and MACEs (aHR, 0.77, 95% CI, 0.60-0.98). Among adult patients with advanced CKD and dyslipidemia, LLD users had a significantly lower risk of composite renal outcomes and MACEs than non-LLD users. In addition to reducing lipid profile, the use of LLD is associated with renal and cardiovascular protective effects.

Adjustment for collider bias in the hospitalized Covid-19 setting

Background

Causal directed acyclic graphs (cDAGs) are frequently used to identify confounding and collider bias. We demonstrate how to use causal directed acyclic graphs to adjust for collider bias in the hospitalized Covid-19 setting.

Materials and methods

According to the cDAGs, three types of modeling have been performed. In model 1, only vaccination is entered as an independent variable. In model 2, in addition to vaccination, age is entered the model to adjust for collider bias due to the conditioning of hospitalization. In model 3, comorbidities are also included for adjustment of collider bias due to the conditioning of hospitalization in different biasing paths intercepting age and comorbidities.

Results

There was no evidence of the effect of vaccination on preventing death due to Covid-19 in model 1. In the second model, where age was included as a covariate, a protective role for vaccination became evident. In model 3, after including chronic diseases as other covariates, the protective effect was slightly strengthened.

Conclusion

Studying hospitalized patients is subject to collider-stratification bias. Like confounding, this type of selection bias can be adjusted for by inclusion of the risk factors of the outcome which also affect hospitalization in the regression model.

Diet Quality and Incident Frailty in Adults 65 Years or Older: The Israeli Longitudinal Study on Aging

OBJECTIVE

To prospectively examine the association between diet quality and frailty incidence in the oldest-old age group.

METHODS

We studied an older adult (65+ years) cohort participating in the Israeli National Health and Nutrition Survey of Older Adults in 2005-2006 (T1 [N=1799]). Survivors of T1 were contacted, and between 2017 and 2019, an extensive interview and a functional assessment were conducted (T2) of 604 past participants. A 24-hour dietary recall, assessed at T1, was used to calculate the Healthy Eating Index (HEI-2015) score. A frailty index based on an accumulation of deficits, including clinical, functional, and cognitive measures, was computed. Frail participants at T1 were excluded from the analysis. Logistic regression models were constructed to assess the association of HEI-2015 score with frailty incidence. Inverse probability weighting was used to minimize selection bias due to attrition.

RESULTS

Of the 479 T2 participants analyzed (mean [SD] age, 84 [5] years; 50% women), 225 (46%) were classified as frail. Frail participants were older, were less educated, and had a lower household income and a higher comorbidity burden at baseline than non-frail participants. After adjustment for sociodemographic and lifestyle factors, a higher HEI-2015 score was associated with decreased odds of incident frailty (odds ratio, 0.57 [95% CI, 0.35 to 0.91] for the upper tertile and 0.66 [95% CI, 0.42 to 1.06] for the middle tertile compared with the lower tertile; Ptrend=.02).

CONCLUSION

In this cohort study of oldest-old participants, improved diet quality was inversely associated with frailty incidence in a dose-dependent manner.

Prevalence of osteosarcopenic obesity and related factors among Iranian older people: Bushehr Elderly Health (BEH) program

Osteosarcopenic obesity is a new syndrome that has been recently discussed in the scientific community. It is a condition that affects the elderly and involves the loss of bone, muscle, and fat tissue. The few studies that have been done on this disease showed that it has a high prevalence among the elderly and can cause various complications. This study was the first one to investigate this syndrome in Iran, and found that its prevalence was 19.83%.

BACKGROUND

Osteosarcopenic obesity syndrome (OSO) is a condition that involves osteopenia/osteoporosis, sarcopenia, and obesity. It leads to a reduction in the quality of life of the elderly and an increase in hospitalization which has attracted the attention of physicians. This study aimed to determine the prevalence and risk factors of osteosarcopenic obesity in people over 60 years of age in Bushehr.

MATERIALS AND METHODS

We used data from the Bushehr study, which included 2426 participants aged ≥ 60 years. We assessed osteoporosis/osteopenia based on T-score; sarcopenia based on hand grip strength, skeletal muscle mass index (SMI), and walking speed; and obesity based on fat mass and BMI for diagnosing OSO. We first examined the factors related to OSO in the univariable analysis and then fitted the multiple logistic regression model, separately for women and men. The result was summarized as adjusted odds ratios with a 95% confidence interval.

RESULTS

In total, 2339 elderly were examined in our study, of which 464 elderly were suffering from osteosarcopenic obesity. The standardized prevalence of OSO was 23.66% (95% CI: 21.15-26.16) in women and 18.53% (95% CI 16.35-20.87) in men. Age was positively linked to osteosarcopenic obesity in both genders and so was diabetes in men. However, education, physical activity, and protein intake were negatively linked to osteosarcopenic obesity in both genders, as well as hypertriglyceridemia and hypertension in women.

CONCLUSION

The prevalence of OSO among men and women of Bushehr city is high and is related to increasing age, low levels of education, physical activity, and protein intake among women and men.

Methanolic extract of S. securidaca flowers, leaves, and seeds' antihyperlipidemic effects on high fat diet-induced hyperlipidemia in Wistar rats

Significant risk factors for atherosclerosis include hyperlipidemia and oxidative stress, which together rank as three of the most significant risk factors for cardiovascular diseases. Securigera securidaca lowers cholesterol levels in diabetic rats' blood. This investigation's objective was to determine how methanolic extracts affected the flowers, leaves, and seeds of plants in rats that were fed a high-fat diet (HFD). Five groups of animals were created (n = 5). A total of 35 days, divided into two intervals, were used for the study. Rats received HFD during the first 15-day interval, while during the second 20-day interval, they also received extracts or the Atorvastatin reference drug. The extract of seeds has a high phenol content as well as DPPH radical antioxidant activity. Extracts were given at a dose of 200 mg/kg; p.o. Methanolic treatment of S. securidaca flowers, leaves, and seeds in HFD-induced hyperlipidemic rats resulted in significant reductions in total cholesterol, triglycerides, LDLC, and VLDL-C levels. HDL-C levels increased significantly because of the leaves. While in hyperlipidemic rats, seeds significantly reduced the activities of the enzymes ALT and ALP. The findings showed that, to a certain extent, seeds, flowers, and leaves may have benefits in reducing hyperlipidemia brought on by HFD in terms of lipid profiles and liver function enzymes. The findings of this study indicate a promising application prospect, but more research is needed to determine the exact mechanism of these novel compounds as antihyperlipidemic agents and to clarify their potential combination effect with synthetic drugs such as Atorvastatin. Combinations can reduce the dose of chemical medications required, which lowers the risk of side effects.

The effect of smoking on latent hazard classes of metabolic syndrome using latent class causal analysis method in the Iranian population

BACKGROUND

The prevalence of metabolic syndrome is increasing worldwide. Clinical guidelines consider metabolic syndrome as an all or none medical condition. One proposed method for classifying metabolic syndrome is latent class analysis (LCA). One approach to causal inference in LCA is using propensity score (PS) methods. The aim of this study was to investigate the causal effect of smoking on latent hazard classes of metabolic syndrome using the method of latent class causal analysis.

METHODS

In this study, we used data from the Tehran Lipid and Glucose Cohort Study (TLGS). 4857 participants aged over 20 years with complete information on exposure (smoking) and confounders in the third phase (2005-2008) were included. Metabolic syndrome was evaluated as outcome and latent variable in LCA in the data of the fifth phase (2014-2015). The step-by-step procedure for conducting causal inference in LCA included: (1) PS estimation and evaluation of overlap, (2) calculation of inverse probability-of-treatment weighting (IPTW), (3) PS matching, (4) evaluating balance of confounding variables between exposure groups, and (5) conducting LCA using the weighted or matched data set.

RESULTS

Based on the results of IPTW which compared the low, medium and high risk classes of metabolic syndrome (compared to a class without metabolic syndrome), no association was found between smoking and the metabolic syndrome latent classes. PS matching which compared low and moderate risk classes compared to class without metabolic syndrome, showed that smoking increases the probability of being in the low-risk class of metabolic syndrome (OR: 2.19; 95% CI: 1.32, 3.63). In the unadjusted analysis, smoking increased the chances of being in the low-risk (OR: 1.45; 95% CI: 1.01, 2.08) and moderate-risk (OR: 1.68; 95% CI: 1.18, 2.40) classes of metabolic syndrome compared to the class without metabolic syndrome.

CONCLUSIONS

Based on the results, the causal effect of smoking on latent hazard classes of metabolic syndrome can be different based on the type of PS method. In adjusted analysis, no relationship was observed between smoking and moderate-risk and high-risk classes of metabolic syndrome.

Association of Maternal Comorbidity Burden With Cesarean Birth Rate Among Nulliparous, Term, Singleton, Vertex Pregnancies

IMPORTANCE

Cesarean birth rate among nulliparous, term, singleton, vertex (NTSV) pregnancies is a standard quality measure in obstetrical care. There are limited data on how the number and type of preexisting conditions affect mode of delivery among primigravidae, and it is also uncertain how maternal comorbidity burden differs across racial and ethnic groups and whether this helps to explain disparities in the NTSV cesarean birth rate.

OBJECTIVE

To determine the association between obstetric comorbidity index (OB-CMI) score and cesarean delivery among NTSV pregnancies and to evaluate whether disparities in mode of delivery exist based on race and ethnicity group after adjusting for covariate factors.

DESIGN, SETTING, AND PARTICIPANTS

This cross-sectional study of deliveries between January 2019 and December 2021 took place across 7 hospitals within a large academic health system in New York and included all NTSV pregnancies identified in the electronic medical record system. Exclusion criteria were fetal demise and contraindication to labor.

EXPOSURE

The OB-CMI score. Covariate factors assessed included race and ethnicity group (American Indian or Alaska Native, Asian or Pacific Islander, Hispanic, non-Hispanic Black, non-Hispanic White, other or multiracial, and declined or unknown), public health insurance, and preferred language.

MAIN OUTCOME AND MEASURES

Cesarean delivery.

RESULTS

A total of 30 253 patients (mean [SD] age, 29.8 [5.4] years; 100% female) were included. Non-Hispanic White patients constituted the largest race and ethnicity group (43.7%), followed by Hispanic patients (16.2%), Asian or Pacific Islander patients (14.6%), and non-Hispanic Black patients (12.2%). The overall NTSV cesarean birth rate was 28.5% (n = 8632); the rate increased from 22.1% among patients with an OB-CMI score of 0 to greater than 55.0% when OB-CMI scores were 7 or higher. On multivariable mixed-effects logistic regression modeling, there was a statistically significant association between OB-CMI score group and cesarean delivery; each successive OB-CMI score group had an increased risk. Patients with an OB-CMI score of 4 or higher had more than 3 times greater odds of a cesarean birth (adjusted odds ratio, 3.14; 95% CI, 2.90-3.40) than those with an OB-CMI score of 0. Compared with non-Hispanic White patients, nearly all other race and ethnicity groups were at increased risk for cesarean delivery, and non-Hispanic Black patients were at highest risk (adjusted odds ratio, 1.43; 95% CI, 1.31-1.55).

CONCLUSIONS AND RELEVANCE

In this cross-sectional study of patients with NTSV pregnancies, OB-CMI score was positively associated with cesarean birth. Racial and ethnic disparities in this metric were observed. Although differences in the prevalence of preexisting conditions were seen across groups, this did not fully explain variation in cesarean delivery rates, suggesting that unmeasured clinical or nonclinical factors may have influenced the outcome.

Impact of Alcohol Consumption on Multiple Sclerosis Using Model-based Standardization and Misclassification Adjustment Via Probabilistic Bias Analysis

BACKGROUND

The etiology of multiple sclerosis (MS) is still not well-demonstrated, and assessment of some risk factors like alcohol consumption has problems like confounding and measurement bias. To determine the causal effect of alcohol consumption on MS after adjusting for alcohol consumption misclassification bias and confounders.

METHODS

In a population-based incident case-control study, 547 patients with MS and 1057 healthy people were recruited. A minimally sufficient adjustment set of confounders was derived using the causal directed acyclic graph. The probabilistic bias analysis method (PBAM) using beta, logit-logistic, and triangular probability distributions for sensitivity/specificity to adjust for misclassification bias in self-reporting alcohol consumption and model-based standardization (MBS) to estimate the causal effect of alcohol consumption were used. Population attributable fraction (PAF) estimates with 95% Monte Carlo sensitivity analysis (MCSA) intervals were calculated using PBAM and MBS analysis. Bootstrap was used to deal with random errors.

RESULTS

The adjusted risk ratio (95% MCSA interval) from the probabilistic bias analysis and MBS between alcohol consumption and MS using the three distribution was in the range of 1.93 (1.07 to 4.07) to 2.02 (1.15 to 4.69). The risk difference (RD) in all three scenarios was 0.0001 (0.0000 to 0.0005) and PAF was in the range of 0.15 (0.010 to 0.50) to 0.17 (0.001 to 0.47).

CONCLUSION

After adjusting for measurement bias, confounding, and random error alcohol consumption had a positive causal effect on the incidence of MS.

Effect of alcohol consumption on breast cancer: probabilistic bias analysis for adjustment of exposure misclassification bias and confounders

PURPOSE

This study was conducted to evaluate the effect of alcohol consumption on breast cancer, adjusting for alcohol consumption misclassification bias and confounders.

METHODS

This was a case-control study of 932 women with breast cancer and 1000 healthy control. Using probabilistic bias analysis method, the association between alcohol consumption and breast cancer was adjusted for the misclassification bias of alcohol consumption as well as a minimally sufficient set of adjustment of confounders derived from a causal directed acyclic graph. Population attributable fraction was estimated using the Miettinen's Formula.

RESULTS

Based on the conventional logistic regression model, the odds ratio estimate between alcohol consumption and breast cancer was 1.05 (95% CI: 0.57, 1.91). However, the adjusted estimates of odds ratio based on the probabilistic bias analysis ranged from 1.82 to 2.29 for non-differential and from 1.93 to 5.67 for differential misclassification. Population attributable fraction ranged from 1.51 to 2.57% using non-differential bias analysis and 1.54-3.56% based on differential bias analysis.

CONCLUSION

A marked measurement error was in self-reported alcohol consumption so after correcting misclassification bias, no evidence against independence between alcohol consumption and breast cancer changed to a substantial positive association.

Prevalence of unpaid caregiving, pain, and depression in older seriously ill patients undergoing elective surgery

INTRODUCTION

Serious illness is a life-limiting condition negatively impacting daily function, quality of life, or excessively straining caregivers. Over 1 million older seriously ill adults undergo major surgery annually, and national guidelines recommend that palliative care be available to all seriously ill patients. However, the palliative care needs of elective surgical patients are incompletely described. Understanding baseline caregiving needs and symptom burden among seriously ill older surgical patients could inform interventions to improve outcomes.

METHODS

Using Health and Retirement Study data (2008-2018) linked to Medicare claims, we identified patients ≥66 years who met an established serious illness definition from administrative data and underwent major elective surgery using Agency for Healthcare Research and Quality (AHRQ) criteria. Descriptive analyses were performed for preoperative patient characteristics, including: unpaid caregiving (no or yes); pain (none/mild or moderate/severe); and depression (no, CES-D < 3, or yes, CES-D ≥ 3). Multivariable regression was performed to examine the association between unpaid caregiving, pain, depression, and in-hospital outcomes, including hospital days (days admitted between discharge date and one-year post-discharge), in-hospital complications (no or yes), and discharge destination (home or non-home).

RESULTS

Of the 1343 patients, 55.0% were female and 81.6% were non-Hispanic White. Mean age was 78.0 (SD 6.8); 86.9% had ≥2 comorbidities. Before admission, 27.3% of patients received unpaid caregiving. Pre-admission pain and depression were 42.6% and 32.8%, respectively. Baseline depression was significantly associated with non-home discharge (OR 1.6, 95% CI 1.2-2.1, p = 0.003), while baseline pain and unpaid caregiving needs were not associated with in-hospital or post-acute outcomes in multivariable analysis.

CONCLUSIONS

Prior to elective surgery, older adults with serious illnesses have high unpaid caregiving needs and a prevalence of pain and depression. Baseline depression alone was associated with discharge destinations. These findings highlight opportunities for targeted palliative care interventions throughout the surgical encounter.

Protective effect of intensive glucose lowering therapy on all-cause mortality, adjusted for treatment switching using G-estimation method, the ACCORD trial

Previous analysis of the action to control cardiovascular risk in diabetes showed an increased risk of mortality among patients receiving intensive glucose lowering therapy using conventional regression method with intention to treat approach. This method is biased when time-varying confounder is affected by the previous treatment. We used 15 follow-up visits of ACCORD trial to compare the effect of time-varying intensive vs. standard treatment of glucose lowering drugs on cardiovascular and mortality outcomes in diabetic patients. The treatment effect was estimated using G-estimation and compared with accelerated failure time model using two modeling strategies. The first model adjusted for baseline confounders and the second adjusted for both baseline and time-varying confounders. While the hazard ratio of all-cause mortality for intensive compared to standard therapy in AFT model adjusted for baseline confounders was 1.17 (95% CI 1.01-1.36), the result of time-dependent AFT model  was compatible with both protective and risk effects. However, the hazard ratio estimated by G-estimation was 0.64 (95% CI 0.39-0.92). The results of this study revealed a protective effect of intensive therapy on all-cause mortality compared with standard therapy in ACCORD trial.

Fast Methods for Drug Approval: Research Perspectives for Pandemic Preparedness

Public heath emergencies such as the outbreak of novel infectious diseases represent a major challenge for drug regulatory bodies, practitioners, and scientific communities. In such critical situations drug regulators and public health practitioners base their decisions on evidence generated and synthesised by scientists. The urgency and novelty of the situation create high levels of uncertainty concerning the safety and effectiveness of drugs. One key tool to mitigate such emergencies is pandemic preparedness. There seems to be, however, a lack of scholarly work on methodology for assessments of new or existing drugs during a pandemic. Issues related to risk attitudes, evidence production and evidence synthesis for drug approval require closer attention. This manuscript, therefore, engages in a conceptual analysis of relevant issues of drug assessment during a pandemic. To this end, we rely in our analysis on recent discussions in the philosophy of science and the philosophy of medicine. Important unanswered foundational questions are identified and possible ways to answer them are considered. Similar problems often have similar solutions, hence studying similar situations can provide important clues. We consider drug assessments of orphan drugs and drug assessments during endemics as similar to drug assessment during a pandemic. Furthermore, other scientific fields which cannot carry out controlled experiments may guide the methodology to draw defeasible causal inferences from imperfect data. Future contributions on methodologies for addressing the issues raised here will indeed have great potential to improve pandemic preparedness.

A practical guide to handling competing events in etiologic time-to-event studies

Competing events are events that preclude the occurrence of the primary outcome. Much has been written on mainly the statistics behind competing events analyses. However, many of these publications and tutorials have a strong statistical tone and might fall short in providing a practical guide to clinician researchers as to when to use a competing event analysis and more importantly which method to use and why. Here we discuss the different target effects in the Fine-Gray and cause-specific methods using simple causal diagrams and provide strengths and limitations of both approaches for addressing etiologic questions. We argue why the Fine-Gray method might not be the best approach for handling competing events in etiological time-to-event studies.

Infarctus du myocarde, accident vasculaire cérébral et psoriasis: une revue systématique des études observationnelles

Patients with psoriasis can have higher rates of hypertension, diabetes mellitus 2, and dyslipidemia. This study aimed to assess the association between psoriasis, myocardial infarction (MI), and stroke. A systematic review was carried out using PubMed/Medline, EMBASE, and LILACS databases searching for observational studies that assessed stroke and/or MI in patients diagnosed with psoriasis vulgaris compared to non-psoriatic patients. A total of 649 articles were identified but only 15 were included in the study. Although there were studies that have observed a significant positive association between psoriasis and MI or stroke, an almost equal number of studies showed no statistically significant association. The relationship between psoriasis and ischemic cardiovascular events is still controversial and it is difficult to establish psoriasis as the etiology of these events.

P-value, compatibility, and S-value

Misinterpretations of P-values and 95% confidence intervals are ubiquitous in medical research. Specifically, the terms significance or confidence, extensively used in medical papers, ignore biases and violations of statistical assumptions and hence should be called overconfidence terms. In this paper, we present the compatibility view of P-values and confidence intervals; the P-value is interpreted as an index of compatibility between data and the model, including the test hypothesis and background assumptions, whereas a confidence interval is interpreted as the range of parameter values that are compatible with the data under background assumptions. We also suggest the use of a surprisal measure, often referred to as the S-value, a novel metric that transforms the P-value, for gauging compatibility in terms of an intuitive experiment of coin tossing.

Longitudinal effects of lipid indices on incident cardiovascular diseases adjusting for time-varying confounding using marginal structural models: 25 years follow-up of two US cohort studies

Background

This study assesses the effect of blood lipid indices and lipid ratios on cardiovascular diseases (CVDs) using inverse probability-of-exposure weighted estimation of marginal structural models (MSMs).

Methods

A pooled dataset of two US representative cohort studies, including 16736 participants aged 42-84 years with complete information at baseline, was used. The effect of each lipid index, including low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), triglyceride (TG), ratios of TC/HDL-C, LDL-C/HDL-C, and TG/HDL-C on coronary heart disease (CHD) and stroke were estimated using weighted Cox regression.

Results

There were 1638 cases of CHD and 1017 cases of stroke during a median follow-up of 17.1 years (interquartile range: 8.5 to 25.7). Compared to optimal levels, the risk of CVD outcomes increased substantially in high levels of TC, LDL-C, TC/HDL-C, and LDL-C/HDL-C. If everyone had always had high levels of TC (≥240 mg/dL), risk of CHD would have been 2.15 times higher, and risk of stroke 1.35 times higher than if they had always had optimal levels (<200 mg/dL). Moreover, if all participants had been kept at very high (≥190 mg/dL) levels of LDL-C, risk of CHD would have been 2.62 times higher and risk of stroke would have been 1.92 times higher than if all participants had been kept at optimal levels, respectively. Our results suggest that high levels of HDL-C may be protective for CHD, but not for stroke. There was also no evidence of an adverse effect of high triglyceride levels on stroke.

Conclusions

Using MSM, this study highlights the effect of TC and LDL-C on CVD, with a stronger effect on CHD than on stroke. There was no evidence for a protective effect of high levels of HDL-C on stroke. Besides, triglyceride was not found to affect stroke.

Adherence to a Mediterranean Diet is associated with physical and cognitive health: A cross-sectional analysis of community-dwelling older Australians

Poor cognitive function is associated with reduced functional independence, risk of institutionalization and reduced health-related quality of life. The ability to independently perform instrumental activities of daily living (iADLs) is compromised in patients with mild cognitive impairment (MCI) or dementia. Emerging evidence suggests that adherence to a Mediterranean diet (MedDiet), may play an important protective role against cognitive decline and dementia risk, whilst preserving functional status. This cross-sectional study aimed to explore the independent associations between MedDiet adherence, cognitive risk, and functional status in community-dwelling older adults living in Australia. MedDiet adherence was assessed using the Mediterranean Diet Adherence Screener (MEDAS); a modified Lawton's iADL scale was used for the assessment of functional status and risk of cognitive impairment was assessed using the AD8 dementia screening intervention. A total of n = 294 participants were included in the final analyses (70.4 ± 6.2 years; Females, n = 201; Males, n = 91; n = 2 unspecified). Adherence to a MedDiet was positively associated with functional ability (β = 0.172; CI: 0.022, 0.132; P = 0.006) independent of age, gender, Body Mass Index (BMI), smoking status, sleep duration, physical activity duration, diabetes status, and level of education. Furthermore, MedDiet adherence was inversely associated with cognitive risk (β = -0.134; CI: -0.198, -0.007; P = 0.035) independent of all covariates. However, our sensitivity analyses further showed that adherence to a MedDiet was not associated with cognitive risk in older adults free from cognitive impairment. We showed that adherence to a MedDiet is associated with healthy physical and cognitive aging. Nevertheless, exploration of these findings in larger cohorts, using longitudinal analyses and controlling for important confounders to ascertain the direction of the relationship is warranted.

Using Causal Diagrams for Biomedical Research

Causal diagrams are used in biomedical research to develop and portray conceptual models that accurately and concisely convey assumptions about putative causal relations. Specifically, causal diagrams can be used for both observational studies and clinical trials to provide a scientific basis for some aspects of multivariable model selection. This methodology also provides an explicit framework for classifying potential sources of bias and enabling the identification of confounder, collider, and mediator variables for statistical analyses. We illustrate the potential serious miscalculation of effect estimates resulting from incorrect selection of variables for multivariable modeling without regard to their type and causal ordering as demonstrated by causal diagrams. Our objective is to improve researchers' understanding of the critical variable selection process to enhance their communication with collaborating statisticians regarding the scientific basis for intended study designs and multivariable statistical analyses. We introduce the concept of causal diagrams and their development as directed acyclic graphs to illustrate the usefulness of this methodology. We present numeric examples of effect estimate calculations and miscalculations based on analyses of the well-known Framingham Heart Study. Clinical researchers can use causal diagrams to improve their understanding of complex causation relations to determine accurate and valid multivariable models for statistical analyses. The Framingham Heart Study dataset and software codes for our analyses are provided in Appendix E1 (available online at http://www.annemergmed.com) to allow readers the opportunity to conduct their analyses.

Interaction Contrasts and Collider Bias

Previous papers have mentioned that conditioning on a binary collider would introduce an association between its causes in at least 1 stratum. In this paper, we prove this statement and, along with intuitions, formally examine the direction and magnitude of the associations between 2 risk factors of a binary collider using interaction contrasts. Among level one of the collider, 2 variables are independent, positively associated, and negatively associated if multiplicative risk interaction contrast is equal to, more than, and less than 0, respectively; the same results hold for the other level of the collider if the multiplicative survival interaction contrast, equal to multiplicative risk interaction contrast minus the additive risk interaction contrast, is compared with 0. The strength of the association depends on the magnitude of the interaction contrast: The stronger the interaction is, the larger the magnitude of the association will be. However, the common conditional odds ratio under the homogeneity assumption will be bounded. A figure is presented that succinctly illustrates our results and helps researchers to better visualize the associations introduced upon conditioning on a collider.

Longitudinal causal effect of modified creatinine index on all-cause mortality in patients with end-stage renal disease: Accounting for time-varying confounders using G-estimation

BACKGROUND

Standard regression modeling may cause biased effect estimates in the presence of time-varying confounders affected by prior exposure. This study aimed to quantify the relationship between declining in modified creatinine index (MCI), as a surrogate marker of lean body mass, and mortality among end stage renal disease (ESRD) patients using G-estimation accounting appropriately for time-varying confounders.

METHODS

A retrospective cohort of all registered ESRD patients (n = 553) was constructed over 8 years from 2011 to 2019, from 3 hemodialysis centers at Kerman, southeast of Iran. According to changes in MCI, patients were dichotomized to either the decline group or no-decline group. Subsequently the effect of interest was estimated using G-estimation and compared with accelerated failure time (AFT) Weibull models using two modelling strategies.

RESULTS

Standard models demonstrated survival time ratios of 0.91 (95% confidence interval [95% CI]: 0.64 to 1.28) and 0.84 (95% CI: 0.58 to 1.23) in patients in the decline MCI group compared to those in no-decline MCI group. This effect was demonstrated to be 0.57 (-95% CI: 0.21 to 0.81) using G-estimation.

CONCLUSION

Declining in MCI increases mortality in patients with ESRD using G-estimation, while the AFT standard models yield biased effect estimate toward the null.

Association of Diet Quality With Longevity and Successful Aging in Israeli Adults 65 Years or Older

IMPORTANCE

To our knowledge, the role of overall diet quality in successful aging has not been conclusively demonstrated.

OBJECTIVE

To prospectively examine the association between diet quality and longevity and successful aging in a population-based cohort of older adults.

DESIGN, SETTING, AND PARTICIPANTS

Participants in "Mabat Zahav" (the Israeli National Health and Nutrition Survey of Older Adults), an older adult cohort (aged ≥65 years) consisting of a random sample of 1770 individuals, were recruited from July 2005 to December 2006 (time 1 [T1]). Survivors of T1 were again contacted and asked to participate in a second interview. From May 2017 to June 2019 (time 2 [T2]), an extensive face-to-face interview and a functional assessment were conducted in each participant's home in a subsample of 604 participants from T1, representing 72.7% of 820 surviving individuals who were able to complete interviews and assessments.

EXPOSURES

A 24-hour dietary recall, assessed at T1, was used to calculate scores from the 2015 version of the Healthy Eating Index (HEI-2015) (scores range from 0 [worst diet] to 100 [best diet]).

MAIN OUTCOMES AND MEASURES

Time to death, with follow-up lasting through June 2019, and successful aging. The latter, based on T2 assessment, was defined as (objectively measured) preserved physical and cognitive function and (subjective) mental well-being and favorable self-rated health. Inverse probability weighting was used in the analysis to minimize attrition bias.

RESULTS

At T1, the study included 1770 participants (mean [SD] age, 74.6 [6.2] years; 943 women [53%]). On average, participants with higher HEI-2015 scores had healthier lifestyles and higher socioeconomic status at T1. During a median follow-up duration of 12.6 years (IQR, 7.6-13.2 years), 893 deaths occurred. Among the 596 T2 participants analyzed (mean [SD] age, 84.1 [4.4] years; 334 [56%] women), 242 (40%) met successful aging criteria. After adjustment for sociodemographic and lifestyle risk factors, a higher HEI-2015 score was inversely associated with mortality (hazard ratios, 0.85; 95% CI, 0.72-0.99 in the upper tertile and 0.83; 95% CI, 0.71-0.98 in the middle tertile vs the lower tertile; P = .04 for trend) and was positively associated with successful aging (odds ratios, 1.73; 95% CI, 1.10-2.72 in the upper tertile and 1.30; 95% CI, 0.83-2.03 in the middle tertile vs the lower tertile; P = .03 for trend).

CONCLUSIONS AND RELEVANCE

In this cohort study of older adults in Israel, improved diet quality was associated with increased longevity and successful aging in a dose-dependent manner. These data contribute to the body of literature that suggests diet quality is associated with aging in the older age group.

Obesity and Diabetic Complications: A Study from the Nationwide Diabetes Report of the National Program for Prevention and Control of Diabetes (NPPCD-2021) Implications for Action on Multiple Scales

BACKGROUND

Obesity plays a major role in the pathogenesis and development of macro- and microvascular complications of type 2 diabetes (T2D) and type 1 diabetes (T1D). We aimed to assess the association between obesity and macrovascular and microvascular complications of diabetes.

METHODS

This study consisted of 111,830 patients (age range: 1-106) with diabetes including 10,641 T1D (3187 obese [38.2% men] and 7454 non-obese [45.5% men]) and 101,189 T2D (51,873 obese [27.5% men] and 49,316 non-obese [33.4% men]) from the National Program for Prevention and Control of Diabetes (NPPCD-2021) in Iran, who attended academic tertiary care outpatient clinics from February 2016 to April 2021. A pooled logistic regression model was used to examine the association between obesity and diabetic complications.

RESULTS

Among patients with T1D, a significant association was found between obesity and cardiovascular disease (CVD), neuropathy, nephropathy and retinopathy (OR= 1.75, 1.56, 1.80 and 1.92, P-value= 0.001, 0.004, 0.001 and <0.001, respectively). In T2D, a statistically significant association was found between obesity and CVD, neuropathy and nephropathy (OR= 1.63, 1.98, 1.21, respectively, P-values <0.001).

CONCLUSION

Obesity was independently associated with CVD, neuropathy and nephropathy in patients with T1D and T2D and with retinopathy only in T1D, to different degrees. The association between obesity and retinopathy and neuropathy was the strongest among T1D and T2D, respectively. Findings from this study suggest that obesity affects diabetic complications differently among the two types of diabetes, in terms of epidemiology and pathophysiology. This signifies the importance of different preventive and therapeutic approaches to obesity in T1D compared to T2D, on a national and global scale.

Contribution of obesity and cardiometabolic risk factors in developing cardiovascular disease: a population-based cohort study

This study aims to assess the effects of central and general adiposity on development of cardiovascular diseases (CVDs) mediated by cardiometabolic risk factors and to analyze their degree of dependency for mediating their effects. To this end, data from the the Tehran Lipid and Glucose Study cohort with 6280 participants were included in this study. The hazard ratios were calculated using a 2-stage regression model in the context of a survival model. Systolic blood pressure (BP), total serum cholesterol, and fasting plasma glucose were designated as mediators. Assessing the interactions revealed that BP was the most important mediator for general ( (HRNIE: 1.11, 95% CI 1.17-1.24) and central obesity (CO) (HRNIE: 1.11, 95% CI 1.07-1.15) with 60% and 36% proportion of the effects mediated in the total population, respectively. The proportion of mediated risk for all three metabolic risk factors was 46% (95% CI 31-75%) for overweight, 66% (45-100%) for general obesity and 52% (39-87%) for central obesity. BP was the most important mediator for overweight and central obesity in men, comprising 29% and 36% of the risk, respectively. The proportion of the risk mediated through all three metabolic risk factors in women was 23% (95% CI 13-50%) for overweight, 36% (21-64%) for general obesity and 52% (39-87%) for central obesity. Based on the results of this study, cardiometabolic mediators have conciliated more than 60% of the adverse effects of high BMI on CVDs in men. Controlling the metabolic risk factors in women does not efficiently contribute to decreasing CVDs as effectively.

Does weight mediate the effect of smoking on coronary heart disease? Parametric mediational g-formula analysis

Background

In settings in which there are time-varying confounders affected by previous exposure and a time-varying mediator, natural direct and indirect effects cannot generally be estimated unbiasedly. In the present study, we estimate interventional direct effect and interventional indirect effect of cigarette smoking as a time-varying exposure on coronary heart disease while considering body weight as a time-varying mediator.

Methods

To address this problem, the parametric mediational g-formula was proposed to estimate interventional direct effect and interventional indirect effect. We used data from the Multi-Ethnic Study of Atherosclerosis to estimate effect of cigarette smoking on coronary heart disease, considering body weight as time-varying mediator.

Results

Over a 11-years period, smoking 20 cigarettes per day compared to no smoking directly (not through weight) increased risk of coronary heart disease by an absolute difference of 1.91% (95% CI: 0.49%, 4.14%), and indirectly decreased coronary heart disease risk by -0.02% (95% CI: -0.05%, 0.04%) via change in weight. The total effect was estimated as an absolute 1.89% increase (95% CI: 0.49%, 4.13%).

Conclusion

The overall absolute impact of smoking to incident coronary heart disease is modest, and we did not discern any important contribution to this effect relayed through changes to bodyweight. In fact, changes in weight because of smoking have no meaningful mediating effect on CHD risk.

Major sex differences in migraine prevalence among occupational categories: a cross-sectional study using UK Biobank

Background

Migraine represents one of the most prevalent neurological conditions worldwide. It is a disabling condition with high impact on the working situation of migraineurs. Interestingly, gender-related differences regarding an association of migraine with important occupational characteristics has been hardly studied.

Methods

The current study scrutinizes gender-specific differences in the prevalence of migraine across a broad spectrum of occupational categories, shedding also light on associations with important job-related features such as shift work, job satisfaction, and physical activity. The study included data from 415 712 participants from the UK Biobank cohort, using the official ICD10 diagnosis of migraine and other health conditions as selection criteria. Prevalence ratios of migraineurs compared to healthy controls among different occupational categories and job-related variables were estimated using log-binomial regression analyses. Statistical models were adjusted for important sociodemographic features such as age, BMI, ethnicity, education and neuroticism. To better highlight specific differences between men and women we stratified by sex.

Results

We detected a differential prevalence pattern of migraine in relation to different job categories between men and women. Especially in men, migraine appears to be more prevalent in highly physically demanding occupations (PR 1.38, 95% CI [0.93, 2.04]). Furthermore, migraine is also more prevalent in jobs that frequently involve shift or night shift work compared to healthy controls. Interestingly, this prevalence is especially high in women (shift work PR 1.45, 95% CI [1.14, 1.83], night shift work PR 1.46, 95% CI [0.93, 2.31]).

Conclusion

Our results show that migraine is genderdependently associated with physically demanding jobs and shift working.

The Effects of Smoking on Metabolic Syndrome and Its Components Using Causal Methods in the Iranian Population

Background

The aim of this study was to estimate the effect of smoking on metabolic syndrome (MS) and its components applying inverse probability-of-treatment weighting (IPTW) and propensity score (PS) matching.

Methods

Using data from Tehran Lipid and Glucose Study, 4857 participants aged over 20 years with information on smoking and confounders in the third phase (2005-2008) were included, and the MS was assessed in the fifth phase (2011-2014). IPTW and PS matching were used to adjust for confounders.

Results

Based on average treatment effect (ATE) estimates, smoking decreased the risk of hypertension (RR: 0.62; 95% CI: 0.43, 0.88), but increased the risk of low HDL cholesterol (1.20; 0.98, 1.48). Similarly, the average treatment effect in the treated (ATT) estimates using IPTW and PS matching suggested that smoking decreased the risk of hypertension (0.63; 0.52, 0.76, and 0.68; 0.54, 0.85), and increased the risk of low HDL cholesterol (1.24; 1.07, 1.43, and 1.28; 1.06, 1.54), respectively.

Conclusions

Smoking seems to increase the risk of low HDL cholesterol but decreases the risk of hypertension.

Population attributable fraction in textbooks: Time to revise

Introduction

The population attributable fraction is an important measure for assessing the impact of intervention on the disease risk in populations, but it is frequently misused in the research literature.

Methods

In this study, we review the definition, calculation, interpretation and assumptions of PAF in 43 textbooks and highlight important shortcomings.

Results

While the Levin formula was proposed as a method of calculation in 29 (67%) textbooks, only in 4 (9%) was the Miettinen formula or its generalization for multilevel exposure recommended to calculate a confounding-adjusted population attributable fraction. Other concepts such as generalized impact fraction and prevented and preventable fractions were briefly discussed in few textbooks.

Discussion

We recommend the authors revise the textbooks in light of our proposed framework for teaching the population attributable fraction.

Estimating the Marginal Causal Effect and Potential Impact of Waterpipe Smoking on Risk of Multiple Sclerosis Using the Targeted Maximum Likelihood Estimation Method: A Large, Population-Based Incident Case-Control Study

There are few if any reports regarding the role of lifetime waterpipe smoking in the etiology of multiple sclerosis (MS). In a population-based incident case-control study conducted in Tehran, Iran, we investigated the association between waterpipe smoking and MS, adjusted for confounders. Cases (n = 547) were patients aged 15-50 years identified from the Iranian Multiple Sclerosis Society between 2013 and 2015. Population-based controls (n = 1,057) were persons aged 15-50 years recruited through random digit telephone dialing. A doubly robust estimation method, the targeted maximum likelihood estimator (TMLE), was used to estimate the marginal risk ratio and odds ratio for the association between waterpipe smoking and MS. The estimated risk ratio and odds ratio were both 1.70 (95% confidence interval: 1.34, 2.17). The population attributable fraction was 21.4% (95% confidence interval: 4.0, 38.8). Subject to the limitations of case-control studies in interpreting associations causally, these results suggest that waterpipe use, or strongly related but undetermined factors, increases the risk of MS. Further epidemiologic studies, including nested case-control studies, are needed to confirm these findings.

The causal effect and impact of reproductive factors on breast cancer using super learner and targeted maximum likelihood estimation: a case-control study in Fars Province, Iran

OBJECTIVES

The relationship between reproductive factors and breast cancer (BC) risk has been investigated in previous studies. Considering the discrepancies in the results, the aim of this study was to estimate the causal effect of reproductive factors on BC risk in a case-control study using the double robust approach of targeted maximum likelihood estimation.

METHODS

This is a causal reanalysis of a case-control study done between 2005 and 2008 in Shiraz, Iran, in which 787 confirmed BC cases and 928 controls were enrolled. Targeted maximum likelihood estimation along with super Learner were used to analyze the data, and risk ratio (RR), risk difference (RD), andpopulation attributable fraction (PAF) were reported.

RESULTS

Our findings did not support parity and age at the first pregnancy as risk factors for BC. The risk of BC was higher among postmenopausal women (RR = 3.3, 95% confidence interval (CI) = (2.3, 4.6)), women with the age at first marriage ≥20 years (RR = 1.6, 95% CI = (1.3, 2.1)), and the history of oral contraceptive (OC) use (RR = 1.6, 95% CI = (1.3, 2.1)) or breastfeeding duration ≤60 months (RR = 1.8, 95% CI = (1.3, 2.5)). The PAF for menopause status, breastfeeding duration, and OC use were 40.3% (95% CI = 39.5, 40.6), 27.3% (95% CI = 23.1, 30.8) and 24.4% (95% CI = 10.5, 35.5), respectively.

CONCLUSIONS

Postmenopausal women, and women with a higher age at first marriage, shorter duration of breastfeeding, and history of OC use are at the higher risk of BC.

Longitudinal Causal Effects of Normalized Protein Catabolic Rate on All-Cause Mortality in Patients With End-Stage Renal Disease: Adjusting for Time-Varying Confounders Using the G-Estimation Method

In this study, we aimed to estimate the causal effect of normalized protein catabolic rate (nPCR) on mortality among end-stage renal disease (ESRD) patients in the presence of time-varying confounding affected by prior exposure using g-estimation. Information about 553 ESRD patients was retrospectively collected over an 8-year period (2011-2019) from hemodialysis facilities in Kerman, Iran. nPCR was dichotomized as <1.2 g/kg/day versus ≥1.2 g/kg/day. Then a standard time-varying accelerated failure time (AFT) Weibull model was built, and results were compared with those generated by g-estimation. After appropriate adjustment for time-varying confounders, weighted g-estimation yielded 78% shorter survival time (95% confidence interval (95% CI): -81, -73) among patients with a continuous nPCR <1.2 g/kg/day than among those who had nPCR ≥1.2 g/kg/day during follow-up, though it was 18% (95% CI: -57, 54) in the Weibull model. Moreover, hazard ratio estimates of 4.56 (95% CI: 3.69, 5.37) and 1.20 (95% CI: 0.66, 2.17) were obtained via weighted g-estimation and the Weibull model, respectively. G-estimation indicated that inadequate dietary protein intake characterized by nPCR increases all-cause mortality among ESRD patients, but the Weibull model provided an effect estimate that was substantially biased toward the null.

No Association Between Maternal Post-partum Depression and Vaccination Uptake of Infants: A Matched Cohort Study in a Large Health Maintenance Organization Database in Israel

BACKGROUND

Maternal post-partum depression is one of the most common medical complications around childbirth. One of its consequences is a possible association with children's receipt of preventive health care, including immunization. This study aimed to explore the association between maternal postpartum depression and children's immunization rates.

METHODS

A retrospective cohort study of Maccabi Healthcare Services (HMO) members comparing immunization rates between children born between 2006 and 2019 to mothers with post-partum depression and children born to mothers with no documented depression. Post-partum depression was assessed by Edinburgh Postnatal Depression Scale, a 10-item questionnaire considered the screening tool of choice in Israel for early Post-partum detection. 1:1 matching was conducted according to criteria: age of the mother ± 2 years, child's year of birth, the newborn baby's gender, the baby's birth order and socioeconomic index. The primary outcome was defined as non-vaccination and the exposure was defined as depression. A sub-analysis was performed, comparing immunization rates of children born to mothers treated with antidepressant medications to rates of children born to untreated mothers.

RESULTS

A total of 709 subjects in the exposed cohort (children born to mothers with post-partum depression symptoms) and 681 subjects in the matched cohort were analyzed. The relative risks among children born to depressed mothers compared with children born to healthy mothers for not receiving any vaccine at 2 months, three doses of pertussis vaccine up to 7 months and four doses of DTaP-Hib-IPV vaccine up to 18 months were 1.15 (95% CI 0.74-1.78), 1.11 (95% CI 0.94-1.31) and 0.82 (95% CI 0.56-1.95), respectively. The relative risks among 139 infants born to treated mothers compared with 570 infants born to untreated mothers for not receiving any vaccine at 2 months, three doses of pertussis vaccine up to 7 months and four doses of DTaP-Hib-IPV vaccine up to 18 months were 1.28 (0.64-2.54), 0.78 (0.57-1.06) and 0.42 (0.17-1.03), respectively.

CONCLUSION

We found no significant association between maternal post-partum depression and uptake of child Immunization.