International journal of epidemiology最新文献

Background: Inconsistent findings regarding health outcomes associated with Supplemental Nutrition Assistance Program (SNAP) use may be influenced by common biases in observational studies. We used negative control methods to evaluate the association between SNAP and cognition while adjusting for unmeasured bias.

Methods: This observational study analysed data from six waves (2008-18) of the Health and Retirement Study-a biennial cohort survey of US adults aged ≥51 years. The analytic sample included 11 942 community-dwelling participants without dementia. SNAP use and household income were self-reported. Global cognitive function (0-27) was assessed via telephone interview. Group differences in cognitive performance were estimated by using three approaches: multiple linear regression, negative control outcome (NCO), and double negative controls (DNCs).

Results: Linear regression models indicated that SNAP users had lower cognitive scores post-SNAP use, with the deficit increasing from -1.48 [95% confidence interval (CI): -1.77, -1.18] in 2010 to -1.84 (95% CI: -2.24, -1.44) in 2018. On the contrary, both the NCO and DNC adjustment results indicated minimal associations between SNAP use and subsequent cognitive performance. NCO estimates ranged from 0.16 (95% CI: -0.23, 0.55) in 2010 to -0.04 (95% CI: -0.57, 0.50) in 2018. DNC estimates ranged from 0.22 (95% CI: -0.40, 0.84) in 2010 to -0.17 (95% CI: -1.06, 0.73). Sensitivity analyses produced similar results.

Conclusion: After common biases were accounted for by using negative controls, SNAP use had little association with cognitive performance. Valid estimates of potential health benefits or harms associated with SNAP may better inform policies and individual decision-making.

Background: Concerns about the consequences of rapid population aging in the USA and England often neglect the key demographic processes of cohort succession and its influence on population health. In this study, we quantify the extent to which trends between 2004 and 2018 in older US and English adults' cognition functioning are related to population composition changes in three areas: (i) age distribution, (ii) socioeconomic factors, and (iii) chronic disease prevalence.

Methods: Using data from the USA-based Health and Retirement Study (n = 17 305 person-years) and the English Longitudinal Study of Aging (n = 7557 person-years), we apply the Kitagawa-Oaxaca-Blinder two-fold decomposition to estimate the contributions of changes in each country's population composition to changes in overall cognitive functioning between 2004 and 2018.

Results: For both men and women, improvements in cognitive functioning were largely driven by cohort succession increasing the average educational attainment of the two populations. Increases in the proportions of the youngest old adults counteracted the negative contributions of increased proportions of the oldest adults. However, increases in the prevalence of psychological conditions (for US men, US women, and English women) and the prevalence of diabetes and divorce (for US women) emerge as specific risk factors that are detrimental to continued gains in cognitive functioning.

Conclusion: Population aging may not necessarily portend an increasing burden of cognitive diseases when cohorts bring different socioeconomic and health protective and risk factors with them into older adulthood.

Background: Previous studies on the reproducibility of 7-day accelerometer measurements have been limited by small sample sizes and short follow-up periods. We aimed to assess the long-term reproducibility of accelerometer-derived physical activity and sleep, and to illustrate the impact of regression dilution bias on the association between daily step count and coronary heart disease (CHD) in UK Biobank.

Methods: We analysed data from 3138 UK Biobank participants in the main accelerometry sub-study with up to four repeat accelerometer measurements after 3-4 years. Nine physical activity and sleep phenotypes were extracted to capture different movement behaviours. Reproducibility was assessed by using intraclass correlation coefficients (ICCs). The impact on disease associations was illustrated by considering daily step count and incident CHD using Cox regression (87 038 participants; 3879 CHD events), before and after correction for regression dilution.

Results: Among the 3138 participants, 51% were women and the mean (SD) age was 63.1 (9.4) years. Reproducibility was good for overall activity, with an ICC (95% confidence interval) of 0.75 (0.74-0.76), and moderate for other phenotypes, with ICCs ranging from 0.58 (0.56-0.59) for sleep efficiency to 0.69 (0.68-0.70) for sedentary behaviour. In our example, the inverse association between daily step count and CHD showed a 20% lower risk of CHD per usual 4000 steps after correcting for regression dilution compared with 13% before correction.

Conclusion: Accelerometer measurements are moderately reproducible and comparable to measures such as blood pressure. Correction for regression dilution bias is crucial to quantify associations of usual physical activity and sleep with disease risk.

Background: Randomized trials comparing new vaccines against tuberculosis for use in neonates and infants, for whom Bacille Calmette-Guérin vaccination is established practice, are using tuberculosis infection as the primary endpoint in a non-inferiority design. Markers of tuberculosis infection have imperfect sensitivity and specificity. Flaws in the non-inferiority trial design typically bias towards non-inferiority, which may result in falsely declaring non-inferiority.

Methods: We conducted a statistical simulation study to assess the impact of imperfect markers of tuberculosis infection on the interpretation of tuberculosis vaccine trials testing a non-inferiority hypothesis of an infection primary outcome in a two-arm randomized comparison. Data were generated in three 2-year cumulative risk of tuberculosis infection scenarios (2%, 5%, and 8%). The specificity of tests of tuberculosis infection was assumed to range from 100% to 85%, while the sensitivity was assumed to range from 100% to 64%. Log-binomial regression was used to estimate the relative risk of tuberculosis infection.

Results: With 100% sensitivity and specificity, type I error and power were both approximately equal to the expected values (2.5% and 80%, respectively) in all three cumulative tuberculosis risk scenarios. With modest deviations from perfect sensitivity and specificity (95% for both), the risk of falsely declaring non-inferiority was 96.8%, 53.2%, and 27.8% in the 2%, 5%, and 8% cumulative tuberculosis risk infection scenarios, respectively.

Discussion: Tuberculosis vaccine non-inferiority trials using an infection primary outcome must be designed and interpreted accounting for the specificity of the tools used to measure infection, otherwise they risk declaring non-inferiority by default.