7 research outputs found
Impact of Selection Bias on Estimation of Subsequent Event Risk.
BACKGROUND: Studies of recurrent or subsequent disease events may be susceptible to bias caused by selection of subjects who both experience and survive the primary indexing event. Currently, the magnitude of any selection bias, particularly for subsequent time-to-event analysis in genetic association studies, is unknown. METHODS AND RESULTS: We used empirically inspired simulation studies to explore the impact of selection bias on the marginal hazard ratio for risk of subsequent events among those with established coronary heart disease. The extent of selection bias was determined by the magnitudes of genetic and nongenetic effects on the indexing (first) coronary heart disease event. Unless the genetic hazard ratio was unrealistically large (>1.6 per allele) and assuming the sum of all nongenetic hazard ratios was <10, bias was usually <10% (downward toward the null). Despite the low bias, the probability that a confidence interval included the true effect decreased (undercoverage) with increasing sample size because of increasing precision. Importantly, false-positive rates were not affected by selection bias. CONCLUSIONS: In most empirical settings, selection bias is expected to have a limited impact on genetic effect estimates of subsequent event risk. Nevertheless, because of undercoverage increasing with sample size, most confidence intervals will be over precise (not wide enough). When there is no effect modification by history of coronary heart disease, the false-positive rates of association tests will be close to nominal
Sociodemographic factors, military service, lifestyle, and cardiovascular disease risk factors in twins with and without obstructive sleep apnea.
Sociodemographic factors, military service, lifestyle, and cardiovascular disease risk factors in twins with and without obstructive sleep apnea.</p
Within-pair and between-pair relationships between the Apnea-Hypopnea Index (AHI) as a continuous variable and total severity score ≥100, in twins discordant for AHI (at least 5-point difference).
The pairwise analysis is also shown for AHI status as a categorical variable.</p
Multivariable analysis of the relationship between the Apnea-Hypopnea Index (AHI), both as a dichotomous variable (AHI ≥15) and as a continuous variable, and total severity score ≥100, in the overall sample with twins treated as individuals.
Multivariable analysis of the relationship between the Apnea-Hypopnea Index (AHI), both as a dichotomous variable (AHI ≥15) and as a continuous variable, and total severity score ≥100, in the overall sample with twins treated as individuals.</p
Myocardial perfusion imaging data in twins with and without obstructive sleep apnea.
Myocardial perfusion imaging data in twins with and without obstructive sleep apnea.</p
Participant flow diagram and construction of the analytical sample.
Participant flow diagram and construction of the analytical sample.</p
Association of a total severity score ≥100, a measure of abnormal myocardial perfusion obtained using positron emission tomography myocardial perfusion imaging, with indicators of obstructive sleep apnea classified in tertiles of their distribution, including the Apnea/Hypopnea Index (AHI), the Respiratory Disturbance Index (RDI), the oxygen desaturation index (ODI), and the cumulative proportion (%) of sleep spent with oxygen saturation (SaO2) < 90%.
P values test the difference between first and third tertile.</p