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Background Among individuals with vitamin D deficiency, daily vitamin D supplementation appears to lower risk of acute respiratory infection. However, recent trials, in different populations and using different regimens, have yielded null results. We investigated the effect of daily vitamin D supplementation (vs placebo) on risk of upper respiratory infection (URI) in older adults. Methods The VITamin D and OmegA-3 TriaL (VITAL) is a randomized, double-blind, placebo-controlled trial of supplemental vitamin D and/or omega-3 fatty acids in generally healthy men (age ≥50 years) and women (age ≥55 years). This prespecified analysis focuses on vitamin D3 (2000 IU/day) versus placebo in the 15 804 (61%) participants with baseline serum total 25-hydroxyvitamin D level. The primary outcome was self-report of a recent URI at 1-year follow-up. Results Participants had a mean age of 68 years and 51% were women; 76% were non-Hispanic White, 16% Black, and 8% other race/ethnicity. The mean 25-hydroxyvitamin D level at baseline was 31 (standard deviation, 10) ng/mL, with <12 ng/mL in 2.4%. The overall effect of vitamin D supplementation on recent URI was nonsignificant (odds ratio [OR], 0.96 [95% confidence interval {CI},.86–1.06]). In the prespecified subgroup of primary interest (<12 ng/mL and denied taking concurrent vitamin D), which had only 255 participants, vitamin D supplementation was nonsignificant (OR, 0.60 [95% CI,.28–1.30]). Statistical power to assess effect modification in other subgroups was limited. Conclusions In older adults not selected for vitamin D deficiency, supplemental vitamin D did not lower URI risk overall. Whether effects differ in subgroups requires further study. Clinical Trials Registration. NCT01169259. [ABSTRACT FROM AUTHOR]

Partially observed confounder data pose challenges to the statistical analysis of electronic health records (EHR) and systematic assessments of potentially underlying missingness mechanisms are lacking. We aimed to provide a principled approach to empirically characterize missing data processes and investigate performance of analytic methods. Methods: Three empirical sub-cohorts of diabetic SGLT2 or DPP4-inhibitor initiators with complete information on HbA1c, BMI and smoking as confounders of interest (COI) formed the basis of data simulation under a plasmode framework. A true null treatment effect, including the COI in the outcome generation model, and four missingness mechanisms for the COI were simulated: completely at random (MCAR), at random (MAR), and two not at random (MNAR) mechanisms, where missingness was dependent on an unmeasured confounder and on the value of the COI itself. We evaluated the ability of three groups of diagnostics to differentiate between mechanisms: 1)-differences in characteristics between patients with or without the observed COI (using averaged standardized mean differences [ASMD]), 2)-predictive ability of the missingness indicator based on observed covariates, and 3)-association of the missingness indicator with the outcome. We then compared analytic methods including "complete case", inverse probability weighting, single and multiple imputation in their ability to recover true treatment effects. Results: The diagnostics successfully identified characteristic patterns of simulated missingness mechanisms. For MAR, but not MCAR, the patient characteristics showed substantial differences (median ASMD 0.20 vs 0.05) and consequently, discrimination of the prediction models for missingness was also higher (0.59 vs 0.50). For MNAR, but not MAR or MCAR, missingness was significantly associated with the outcome even in models adjusting for other observed covariates. Comparing analytic methods, multiple imputation using a random forest algorithm resulted in the lowest root-mean-squared-error. Conclusion: Principled diagnostics provided reliable insights into missingness mechanisms. When assumptions allow, multiple imputation with nonparametric models could help reduce bias. [ABSTRACT FROM AUTHOR]

Background: We illustrate a method for stratum assignment in small cohort studies that avoids modeling assumptions. Methods: Off-the-shelf software (rgenoud) made stratum assignments to minimize a loss function built on within-stratum and populationadjusted Euclidean distances. Results: In 100 trials using simulated data of 300 records with a binary treatment and four dissimilar covariate treatment predictors, minimizing a loss based on Euclidean distance reduced covariate imbalance by a median of 99%. Stratification by propensity score and weighting records by the inverse of their probability of treatment reduced imbalance by 76%-89% and 83%-94%, respectively. Loss minimization applied to a cohort of 361 children undergoing immunotherapy achieved nearly complete elimination of covariate differences for important treatment predictors. Conclusion: With the availability of semiparametric stratumassignment algorithms, analysts can tailor loss functions to meet design goals. Here, a loss function that emphasized covariate balance performed well under limited testing. [ABSTRACT FROM AUTHOR]

ImportanceObservational studies suggest a role for dietary nutrients such as vitamin E and selenium in cataract prevention. However, the results of randomized clinical trials of vitamin E supplements and cataract have been disappointing and are not yet available for selenium.ObjectiveTo test whether long-term supplementation with selenium and vitamin E affects the incidence of cataract in a large cohort of men.Design, setting, and participantsThe Selenium and Vitamin E Cancer Prevention Trial (SELECT) Eye Endpoints Study was an ancillary study of the Southwest Oncology Group-coordinated SELECT, a randomized placebo-controlled 4-arm trial of selenium and vitamin E conducted among 35,533 men, 50 years and older for African American participants and 55 years and older for all other men, at 427 participating sites in the United States, Canada, and Puerto Rico. A total of 11,267 SELECT participants from 128 SELECT sites participated in the SELECT Eye Endpoints ancillary study.InterventionsIndividual supplements of selenium (200 μg per day from L-selenomethionine) and vitamin E (400 IU per day of all rac-α-tocopheryl acetate).Main outcomes and measuresIncident cataract was defined as a lens opacity, age related in origin, and responsible for a reduction in best-corrected visual acuity to 20/30 or worse based on self-reports confirmed by medical record review. Cataract extraction was defined as the surgical removal of an incident cataract.ResultsDuring a mean (SD) of 5.6 (1.2) years of treatment and follow-up, 389 cases of cataract were documented. There were 185 cataracts in the selenium group and 204 in the no selenium group (hazard ratio, 0.91; 95 % CI, 0.75-1.11; P = .37). For vitamin E, there were 197 cases in the treated group and 192 in the placebo group (hazard ratio, 1.02; 95 % CI, 0.84-1.25; P = .81). Similar results were observed for cataract extraction.Conclusions and relevanceThese data from a large cohort of apparently healthy men indicate that long-term daily supplementation with selenium and/or vitamin E is unlikely to have a large beneficial effect on age-related cataract.Trial registrationClinicalTrials.gov Identifier: NCT00784225.

Purpose: For observational cohort studies that employ matching by propensity scores (PS), preliminary stratification by consequential predictors of outcome better emulates stratified randomization and potentially reduces variance and bias through relaxed dependence on modeling assumptions. We assessed the impact of pre‐stratification in two real‐life examples. For both, prior evidence from placebo‐controlled randomized clinical trials (RCTs) suggested small or no risk reduction, but observational analysis suggested protection, presumably the result of confounding bias. Study Design and Setting: The study populations consisted of Medicare beneficiaries (2014‐18) with type 2 diabetes initiating either (i) empagliflozin versus dipeptidyl peptidase‐4 inhibitors (DPP‐4i) or (ii) empagliflozin versus glucagon‐like peptide‐1 receptor agonists (GLP‐1RA). The outcome was myocardial infarction or stroke. We estimated hazard ratios (HR) and rate differences (RD) after controlling for 143 pre‐exposure covariates via 1:1 PS matching after (1) PS estimation in the total cohort (total‐cohort PS‐matching) and (2) PS estimation separately by baseline cardiovascular disease (stratified PS matching). Results: Stratified PS matching resulted in HRs that exceeded those from total‐cohort PS‐matching by 13% and 9%, respectively, for the comparisons of empagliflozin to DPP‐4i and GLP‐1RA. Against both comparators, HRs and RDs after stratified PS matching were closer to the null, with slightly higher variances (2%–3%) than those after total‐cohort PS matching. Conclusion: Stratified PS matching produced effect estimates closer to the expected trial findings than total‐cohort PS matching. The price paid in increased variance was minimal. [ABSTRACT FROM AUTHOR]

ObjectivesResearch about work-related stressors and cardiovascular disease (CVD) has produced mixed findings. Moreover, a paucity of data exists regarding the long-term associations between job strain and job insecurity and CVD among women.MethodsWe used Cox proportional hazard models to examine the relationship between job strain, job insecurity, and incident CVD over 10 years of follow-up among 22,086 participants in the Women's Health Study (mean age 57±5 years).ResultsDuring 10 years of follow-up there were 170 myocardial infarctions (MI), 163 ischemic strokes, 440 coronary revascularizations, and 52 CVD deaths. In models adjusted for age, race, education, and income, women with high job strain (high demand, low control) were 38% more likely to experience a CVD event than their counterparts who reported low job strain (low demand, high control; Rate Ratio (RR) = 1.38, 95% Confidence Interval (CI) = 1.08-1.77), and women with active jobs (high demand, high control) were 38% more likely to experience a CVD event relative to women who reported low job strain (95% CI = 1.07-1.77). Outcome-specific analyses revealed that high job strain predicted non-fatal myocardial infarction (RR = 1.67, CI = 1.04-2.70), and coronary revascularization (RR = 1.41, CI = 1.05-1.90). No evidence of an association between job insecurity and long-term CVD risk was observed.ConclusionHigh strain and active jobs, but not job insecurity, were related to increased CVD risk among women. Both job strain and job insecurity were significantly related to CVD risk factors. With the increase of women in the workforce, these data emphasize the importance of addressing job strain in CVD prevention efforts among working women.