Methods matter: population attributable fraction (PAF) in sport and exercise medicine

Global and regional burden estimation of HIV-associated non-Hodgkin's lymphoma: a meta-analysis and modelling analysis protocol

INTRODUCTION

HIV infection is one of the complex aetiologies of non-Hodgkin's lymphoma (NHL). However, the contribution of HIV to burden of NHL across time and region has not yet been comprehensively reported and quantified. Thus, this study aims to evaluate the relative risk of NHL in individuals with HIV infection compared with those without by performing a comprehensive meta-analysis. Additionally, we intend to further estimate quantitatively the degree of HIV contributing to burden of NHL using population attributable fraction (PAF) modelling analysis.

METHODS AND ANALYSIS

This study will screen a mass of records searched from four electronic databases (PubMed, Embase, Cochrane Library and Web of Science). The main outcomes are specific effect values and corresponding 95% CIs for NHL among population with HIV infection compared with those without to quantify the association between HIV infection and NHL. After quality assessment and data extraction, we will undertake a meta-analysis to calculate the pooled risk ratio (RR). Furthermore, PAF calculation based on pooled RR combines with number of age-specific disability-adjusted life year (DALY) and HIV prevalence data (aged ≥15 years old) from 1990 to 2019, at global, regional and country levels. We will calculate the PAF, HIV-associated DALY number and age-standardised rate to quantify the burden of HIV-associated NHL.

ETHICS AND DISSEMINATION

This study is based on published articles; thus, the ethic approval is not essential. In addition, we intend to publish the results on peer-reviewed journals for more discussion. We believe that research on estimating global burden of NHL can provide valuable insights for developing targeted prevention and control strategies, thereby achieving significant benefits.

PROSPERO REGISTRATION NUMBER

CRD 42023404150.

Population modifiable risk factors associated with under-5 acute respiratory tract infections and diarrhoea in 25 countries in sub-Saharan Africa (2014-2021): an analysis of data from demographic and health surveys

Background

Identifying the critical modifiable risk factors for acute respiratory tract infections (ARIs) and diarrhoea is crucial to reduce the burden of disease and mortality among children under 5 years of age in sub-Saharan Africa (SSA) and ultimately achieving the Sustainable Development Goals (SDGs). We investigated the modifiable risk factors of ARI and diarrhoea among children under five using nationally representative surveys.

Methods

We used the most recent demographic and health survey (DHS) data (2014-2021) from 25 SSA countries, encompassing a total of 253,167 children. Countries were selected based on the availability of recent datasets (e.g., DHS-VII or DHS-VIII) that represent the current socioeconomic situations. Generalised linear latent mixed models were used to compute odds ratios (ORs). Population attributable fractions (PAFs) were calculated using adjusted ORs and prevalence estimates for key modifiable risk factors among ARI and diarrhoeal cases.

Findings

This study involved 253,167 children, with a mean age of 28.7 (±17.3) months, and 50.5% were male. The highest PAFs for ARI were attributed to unclean cooking fuel (PAF = 15.7%; 95% CI: 8.1, 23.1), poor maternal education (PAF = 13.4%; 95% CI: 8.7, 18.5), delayed initiation of breastfeeding (PAF = 12.4%; 95% CI: 9.0, 15.3), and poor toilets (PAF = 8.5%; 95% CI: 4.7, 11.9). These four modifiable risk factors contributed to 41.5% (95% CI: 27.2, 52.9) of ARI cases in SSA. The largest PAFs of diarrhoea were observed for unclean cooking fuel (PAF = 17.3%; 95% CI: 13.5, 22.3), delayed initiation of breastfeeding (PAF = 9.2%; 95% CI: 7.5, 10.5), household poverty (PAF = 7.0%; 95% CI: 5.0, 9.1) and poor maternal education (PAF = 5.6%; 95% CI: 2.9, 8.8). These four modifiable risk factors contributed to 34.0% (95% CI: 26.2, 42.3) of cases of diarrhoea in SSA.

Interpretation

This cross-sectional study identified four modifiable risk factors for ARI and diarrhoea that should be a priority for policymakers in SSA. Enhancing home-based care and leveraging female community health workers is crucial for accelerating the reduction in under-5 mortality linked to ARI and diarrhoea in SSA.

Funding

None.

Sleep disordered breathing and neurobehavioral deficits in children and adolescents: a systematic review and meta-analysis

BACKGROUND

Sleep disordered breathing (SDB) is broadly recognized to be associated with neurobehavioral deficits, which have significant impacts on developing-aged children and adolescents. Therefore, our study aimed to quantify the proportion of neurobehavioral impairments attributed to SDB in general children and adolescents by population attributable fraction (PAF).

METHODS

The study was registered at PROSPERO (ID: CRD42023388143). We collected two types of literature on the prevalence of SDB and the risk of SDB-related neurobehavioral deficits from ten electronic databases and registers, respectively. The pooled effect sizes (Pe, Pc, RR) by random-effects meta-analysis were separately substituted into Levin's formula and Miettinen's formula to calculate PAFs.

RESULTS

Three prevalence literature and 2 risk literature, all with moderate/high quality, were included in the quantitative analysis individually. The prevalence of SDB was 11% (95%CI 2%-20%) in children and adolescents (Pe), while the SDB prevalence was 25% (95%CI 7%-42%) in neurobehavioral patients (Pc). SDB diagnosis at baseline was probably associated with about threefold subsequent incidence of neurobehavioral deficits (pooled RR 3.24, 95%CI 1.25-8.41), after multi-adjustment for key confounders. Up to 19.8% or 17.3% of neurobehavioral consequences may be attributed to SDB from Levin's formula and Miettinen's formula, respectively.

CONCLUSIONS

A certain number of neurobehavioral consequences may be attributable to SDB. It is essential for clinicians to identify and treat SDB timely, as well as screen for SDB in patients with neurobehavioral impairments. More longitudinal studies of SDB and neurobehavioral deficits are needed in the future to further certify the association between them.

Estimates of the global burden of non-Hodgkin lymphoma attributable to HIV: a population attributable modeling study

Background

Human immunodeficiency virus (HIV) significantly increases the risk of non-Hodgkin lymphoma (NHL) development, yet the population-level impact on NHL burden is unquantified. We aim to quantify this association and estimate the global burden of HIV-associated NHL.

Methods

In this meta-analysis, we searched five databases (PubMed, EMBASE, Cochrane Library, Web of Science, Scopus) from database inception up to September 13, 2023, identifying cohort, case-control, or cross-sectional studies with an effective control group to assess NHL risk among individuals with HIV infection, with two authors extracting summary data from reports. Global and regional HIV-associated population attributable fraction (PAF) and NHL disease burden were calculated based on the pooled risk ratio (RR). HIV prevalence and NHL incidence were obtained from the Joint United Nations Programme on HIV/AIDS (UNAIDS) and Global Burden of Diseases, Injuries, and Risk Factors Study 2019. Trends in NHL incidence due to HIV were assessed using age-standardised incidence rate (ASIR) and estimated annual percentage change (EAPC). This study was registered with PROSPERO (CRD42023404150).

Findings

Out of 14,929 literature sources, 39 articles met our inclusion criteria. The risk of NHL was significantly increased in the population living with HIV (pooled RR 23.51, 95% CI 17.62-31.37; I2 = 100%, p < 0.0001), without publication bias. Globally, 6.92% (95% CI 2.18%-11.57%) of NHL new cases in 2019 were attributable to HIV infection (30,503, 95% CI 9585-52,209), which marked a more than three-fold increase from 1990 (8340, 95% CI 3346-13,799). The UNAIDS region of Eastern and Southern Africa was the highest affected region, with 44.46% (95% CI 19.62%-58.57%) of NHL new cases attributed to HIV infection. The Eastern Europe and Central Asia region experienced the highest increase in ASIR of NHL due to HIV in the past thirty years, wherein the EAPC was 8.74% (95% CI 7.66%-9.84%), from 2010 to 2019.

Interpretation

People with HIV infection face a significantly increased risk of NHL. Targeted prevention and control policies are especially crucial for countries in Eastern and Southern Africa, Eastern Europe and Central Asia, to achieve the UNAIDS's '90-90-90' Fast-Track targets. Limited studies across diverse regions and heterogeneity between research have hindered precise estimations for specific periods and regions.

Funding

Sichuan Provincial People's Hospital, Chengdu, China; Health Care for Cadres of Sichuan Province, Chengdu, China; Science and Technology Department of Sichuan Province, Chengdu, China.

Economic costs of obesity: a systematic review

INTRODUCTION

Obesity is a growing public health problem leading to substantial economic impact. This study aimed to summarize the economic impact of obesity and to critically analyze the methods used in the cost-of-illness (COI) studies on obesity.

METHODS

We conducted systematic search in PubMed and Scopus from September 1, 2016, to July 22, 2022. Original COI studies estimating the economic cost of obesity and/or overweight in at least one country, published in English were included. To facilitate the comparison of estimates across countries, we converted the cost estimates of different years to 2022 purchasing power parity (PPP) values using each country's consumer price index (CPI) and PPP conversion rate.

RESULTS

Nineteen studies were included. All studies employed a prevalence-based approach using Population Attributable Fraction (PAF) methodology. About half of the included studies (53%) were conducted in high-income countries while the others (47%) were conducted in middle-income countries. The economic burden of obesity ranged between PPP 15 million in Brazil to PPP 126 billion in the USA, in the year 2022. Direct medical costs accounted for 0.7% to 17.8% of the health system expenditure. Furthermore, the total costs of obesity ranged from 0.05% to 2.42% of the country's gross domestic product (GDP). Of the seven studies that estimated both direct and indirect costs, indirect costs accounted for the largest portion of five studies. Nevertheless, a variety in methodology across studies was identified. The number of co-morbidities included in the analysis varied across studies.

CONCLUSIONS

Although there was a variety of methodologies across studies, consistent evidence indicated that the economic burden of obesity was substantial. Obesity prevention and control should be a public health priority, especially among countries with high prevalence of obesity.

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.

Impact of hypertension prevalence trend on mortality and burdens of dementia and disability in England and Wales to 2060: a simulation modelling study

BACKGROUND

Previous estimates of the impact of public health interventions targeting hypertension usually focus on one health outcome. This study aims to consider the effects of change in future hypertension prevalence on mortality, dementia, and disability simultaneously.

METHODS

We modelled three plausible scenarios based on observed trends of hypertension prevalence from 2003 to 2017 in England: observed trends continue (baseline scenario); 2017 prevalence remains unchanged; and 2017 prevalence decreases by 50% by 2060. We used a probabilistic Markov model to integrate calendar trends in incidence of cardiovascular disease, dementia, disability, and mortality to forecast their future occurrence in the population of England and Wales. Assuming the hypertension prevalence trend modifies health transition probabilities, we compared mortality outcomes and the burden of dementia and disability to 2060 for the scenarios.

FINDINGS

If the decline in hypertension prevalence stops, there would be a slight increase in the number of additional deaths to 2060 (22·9 [95% uncertainty interval 19·0-26·6] more deaths per 100 000 population), although the burdens of disability and dementia in absolute terms would change little. Alternatively, if the downward hypertension prevalence trend accelerates (with prevalence falling by 50% between 2017 and 2060), there would be a modest additional reduction in deaths (57·0 [50·4-63·5] fewer deaths per 100 000 population), a small increase in dementia burden (9·0 [5·1-13·2] more cases per 100 000 population), no significant effect on disability burden, and an 8% gain in healthy life expectancy at age 65 years from 2020 to 2060 (5·3 years vs 4·9 years) compared with the baseline scenario.

INTERPRETATION

The major future impact of alternative hypertension prevention strategies appears to be on future life expectancy. The salutary effect of lower population blood pressure distribution on incidence of dementia and disability might not offset expansion of the susceptible population due to reduced mortality.

FUNDING

British Heart Foundation and UK Economic and Social Research Council.

Early childhood lower respiratory tract infection and premature adult death from respiratory disease in Great Britain: a national birth cohort study

BACKGROUND

Lower respiratory tract infections (LRTIs) in early childhood are known to influence lung development and lifelong lung health, but their link to premature adult death from respiratory disease is unclear. We aimed to estimate the association between early childhood LRTI and the risk and burden of premature adult mortality from respiratory disease.

METHODS

This longitudinal observational cohort study used data collected prospectively by the Medical Research Council National Survey of Health and Development in a nationally representative cohort recruited at birth in March, 1946, in England, Scotland, and Wales. We evaluated the association between LRTI during early childhood (age <2 years) and death from respiratory disease from age 26 through 73 years. Early childhood LRTI occurrence was reported by parents or guardians. Cause and date of death were obtained from the National Health Service Central Register. Hazard ratios (HRs) and population attributable risk associated with early childhood LRTI were estimated using competing risks Cox proportional hazards models, adjusted for childhood socioeconomic position, childhood home overcrowding, birthweight, sex, and smoking at age 20-25 years. We compared mortality within the cohort studied with national mortality patterns and estimated corresponding excess deaths occurring nationally during the study period.

FINDINGS

5362 participants were enrolled in March, 1946, and 4032 (75%) continued participating in the study at age 20-25 years. 443 participants with incomplete data on early childhood (368 [9%] of 4032), smoking (57 [1%]), or mortality (18 [<1%]) were excluded. 3589 participants aged 26 years (1840 [51%] male and 1749 [49%] female) were included in the survival analyses from 1972 onwards. The maximum follow-up time was 47·9 years. Among 3589 participants, 913 (25%) who had an LRTI during early childhood were at greater risk of dying from respiratory disease by age 73 years than those with no LRTI during early childhood (HR 1·93, 95% CI 1·10-3·37; p=0·021), after adjustment for childhood socioeconomic position, childhood home overcrowding, birthweight, sex, and adult smoking. This finding corresponded to a population attributable risk of 20·4% (95% CI 3·8-29·8) and 179 188 (95% CI 33 806-261 519) excess deaths across England and Wales between 1972 and 2019.

INTERPRETATION

In this prospective, life-spanning, nationally representative cohort study, LRTI during early childhood was associated with almost a two times increased risk of premature adult death from respiratory disease, and accounted for one-fifth of these deaths.

FUNDING

National Institute for Health and Care Research Imperial Biomedical Research Centre, Royal Brompton and Harefield National Health Service (NHS) Foundation Trust, Royal Brompton and Harefield Hospitals Charity and Imperial College Healthcare NHS Trust, UK Medical Research Council.

Population-level contribution of interpersonal discrimination to psychological distress among Australian Aboriginal and Torres Strait Islander adults, and to Indigenous-non-Indigenous inequities: cross-sectional analysis of a community-controlled First Nations cohort study

BACKGROUND

International and population-specific evidence identifies elevated psychological distress prevalence among those experiencing interpersonal discrimination. We aim to quantify the potential whole-of-population contribution of interpersonal discrimination to psychological distress prevalence and Indigenous-non-Indigenous gaps in Australia.

METHODS

We did a cross-sectional analysis of data from Mayi Kuwayu: the National Study of Aboriginal and Torres Strait Islander Wellbeing. Baseline surveys were completed between June 8, 2018, and Sept 28, 2022. We analysed responses from participants who were aged 18 years or older at survey completion, whose surveys were processed between Oct 1, 2018, and May 1, 2021. Sample weights were developed on the basis of national population benchmarks. We measured everyday discrimination using an eight-item measure modified from the Everyday Discrimination Scale and classified experiences as racial discrimination if participants attributed these experiences to their Indigeneity. Psychological distress was measured using a validated, modified Kessler-5 scale. Applying logistic regression, we calculated unadjusted odds ratios (ORs), to approximate incident rate ratios (IRRs), for high or very high psychological distress in relation to everyday discrimination and everyday racial discrimination across age-gender strata. Population attributable fractions (PAFs), under the hypothetical assumption that ORs represent causal relationships, were calculated using these ORs and population-level exposure prevalence. These PAFs were used to quantify the contribution of everyday racial discrimination to psychological distress gaps between Indigenous and non-Indigenous adults.

FINDINGS

9963 survey responses were eligible for inclusion in our study, of which we analysed 9951 (99·9%); 12 were excluded due to responders identifying as a gender other than man or woman (there were too few responses from this demographic to be included as a category in stratified tables or adjusted analyses). The overall prevalence of psychological distress was 48·3% (95% CI 47·0-49·6) in those experiencing everyday discrimination compared with 25·2% (23·8-26·6) in those experiencing no everyday discrimination (OR 2·77 [95% CI 2·52-3·04]) and psychological distress prevalence was 49·0% (95% CI 47·3-50·6) in those experiencing everyday racial discrimination and 31·8% (30·6-33·1) in those experiencing no everyday racial discrimination (OR 2·06 [95% CI 1·88-2·25]. Overall, 49·3% of the total psychological distress burden among Aboriginal and Torres Strait Islander adults could be attributable to everyday discrimination (39·4-58·8% across strata) and 27·1% to everyday racial discrimination. Everyday racial discrimination could explain 47·4% of the overall gap in psychological distress between Indigenous and non-Indigenous people (40·0-60·3% across strata).

INTERPRETATION

Our findings show that interpersonal discrimination might contribute substantially to psychological distress among Aboriginal and Torres Strait Islander adults, and to inequities compared with non-Indigenous adults. Estimated PAFs include contributions from social and health disadvantage, reflecting contributions from structural racism. Although not providing strictly conclusive evidence of causality, this evidence is sufficient to indicate the psychological harm of interpersonal discrimination. Findings add weight to imperatives to combat discrimination and structural racism at its core. Urgent individual and policy action is required of non-Indigenous people and colonial structures, directed by Aboriginal and Torres Strait Islander peoples.

FUNDING

National Health and Medical Research Council of Australia, Ian Potter Foundation, Australian Research Council, US National Institutes of Health, and Sierra Foundation.

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.

A CHecklist for statistical Assessment of Medical Papers (the CHAMP statement): explanation and elaboration

Misuse of statistics in medical and sports science research is common and may lead to detrimental consequences to healthcare. Many authors, editors and peer reviewers of medical papers will not have expert knowledge of statistics or may be unconvinced about the importance of applying correct statistics in medical research. Although there are guidelines on reporting statistics in medical papers, a checklist on the more general and commonly seen aspects of statistics to assess when peer-reviewing an article is needed. In this article, we propose a CHecklist for statistical Assessment of Medical Papers (CHAMP) comprising 30 items related to the design and conduct, data analysis, reporting and presentation, and interpretation of a research paper. While CHAMP is primarily aimed at editors and peer reviewers during the statistical assessment of a medical paper, we believe it will serve as a useful reference to improve authors' and readers' practice in their use of statistics in medical research. We strongly encourage editors and peer reviewers to consult CHAMP when assessing manuscripts for potential publication. Authors also may apply CHAMP to ensure the validity of their statistical approach and reporting of medical research, and readers may consider using CHAMP to enhance their statistical assessment of a paper.

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.

The association between hormonal contraceptive use and glaucoma in women of reproductive age

AIMS

We aimed to investigate the association between hormonal contraceptive (HC) use and the incidence of glaucoma in females of reproductive age with a focus on duration and type of HCs used.

METHODS

A retrospective cohort study with a case-control analysis (nested case-control) was undertaken using data from IQVIA's electronic medical record (IQVIA, USA) from 2008 to 2018. Within a cohort of 4 871 504 women, cases of glaucoma or ocular hypertension were identified. Subjects were followed to the first diagnosis of glaucoma. Each glaucoma case was matched to four controls by age, body mass index and follow up time. The main outcome measure was the first diagnosis of glaucoma defined by the first ICD-9/10 code for glaucoma or ocular hypertension.

RESULTS

Among 4 871 504 women identified, there were 2366 cases of glaucoma and 9464 controls. Regular users of hormonal contraceptives had an elevated risk of glaucoma compared to non-users with an adjusted incident rate ratio (aIRR) of 1.57 (95% CI: 1.29-1.92). Current users were of greatest risk (aIRR of 2.38, 95% CI: 1.81-3.13), whereas the aIRR among past users was 1.08 (95% CI: 0.82-1.43). The aIRR for glaucoma increased from 0.82 (95% CI: 0.70-0.95) among those with one or two prescriptions in the 2 years prior to the first diagnosis of glaucoma to 1.54 (95% CI: 1.32-1.81) among those with greater than four prescriptions.

CONCLUSIONS

This nested case-control study demonstrated an elevated risk, albeit low, of glaucoma in females of reproductive age who use regular hormonal contraception. Future studies are needed to confirm these findings.

Estimation of Generalized Impact Fraction and Population Attributable Fraction of Hypertension Based on JNC-IV and 2017 ACC/AHA Guidelines for Cardiovascular Diseases Using Parametric G-Formula: Tehran Lipid and Glucose Study (TLGS)

Purpose

An area of interest to health policymakers is the effect of interventions aimed at risk factors on decreasing the number of new cardiovascular disease (CVD) cases. The aim of this study was to estimate the generalized impact fraction (GIF) and population attributable fraction (PAF) of hypertension (HTN) for CVD in Tehran.

Patients and Methods

In this population-based cohort study, 8071 participants aged ≥30 years were followed for a median of 16 years. A survival model was used to estimate the 10- and 18-year risk of CVD. JNC-IV and 2017 ACC/AHA guidelines were used to categorize blood pressure (BP). PAF and GIF were estimated in different scenarios using the parametric G-formula.

Results

Of 7378 participants included in analyses, 22.7% and 52.3% were classified as hypertensive according to the JNC-IV and 2017 ACC/AHA guidelines, respectively. According to the 2017 ACC/AHA, the 10-year risk of CVD was 5.1% (4.3–6.0%), 8.9% (6.7–12.0%), and 7.1% (6.1–8.4%) for normal BP, elevated BP, and stage 1 HTN, respectively, and 20.8% (18.8–23.0%) for stage 2 of the 2017 ACC/AHA and JNC-IV. The PAF of stage 2 vs stage 1 and vs normal BP for CVD was 17.4% (11.5–21.8%) and 20.4% (14.6–26.4%), respectively. The GIF of 30% reduction in the prevalence of stage 2 HTN to stage 1 and to normal BP for CVD was 5.1% (3.4–6.6%) and 6.1% (4.4–8.0%), respectively. Based on JNC-IV, the PAF and GIF of 30% for CVD were 17.8% (12.7–22.9%) and 5.4% (4.0–6.9%), respectively.

Conclusion

By reducing the prevalence of HTN by 30%, a remarkable number of new CVD cases would be prevented. In an Iranian population, the comparison of HTN cases with normal BP showed no association between stage 1 HTN and CVD, whereas elevated BP was a significant risk factor for the incidence of CVD.

Effect of Smoking on Breast Cancer by Adjusting for Smoking Misclassification Bias and Confounders Using a Probabilistic Bias Analysis Method

Purpose

The aim of this study was to determine the association between smoking and breast cancer after adjusting for smoking misclassification bias and confounders.

Methods

In this case–control study, 1000 women with breast cancer and 1000 healthy controls were selected. Using a probabilistic bias analysis method, the association between smoking and breast cancer was adjusted for the bias resulting from misclassification of smoking secondary to self-reporting as well as a minimally sufficient adjustment set of confounders derived from a causal directed acyclic graph (cDAG). Population attributable fraction (PAF) for smoking was calculated using Miettinen’s formula.

Results

While the odds ratio (OR) from the conventional logistic regression model between smoking and breast cancer was 0.64 (95% CI: 0.36–1.13), the adjusted ORs from the probabilistic bias analysis were in the ranges of 2.63–2.69 and 1.73–2.83 for non-differential and differential misclassification, respectively. PAF ranges obtained were 1.36–1.72% and 0.62–2.01% using the non-differential bias analysis and differential bias analysis, respectively.

Conclusion

After misclassification correction for smoking, the non-significant negative-adjusted association between smoking and breast cancer changed to a significant positive-adjusted association.