Accounting for Unobservable Exposure Time Bias When Using Medicare Prescription Drug Data
Objective: To describe the prevalence and correlates of unobservable medication exposure time, and to recommend approaches for minimizing bias, in studies using Medicare Part D data.
Sample: 179,065 Medicare patients hospitalized for an AMI in 2007 or 2008.
Methods: We compared two methods for creating medication exposure observation periods using acute care discharge vs. post-acute care discharge dates. We examined options for increasing cohort sizes by requiring different thresholds for observable days, or by using as a covariate, in the observation period. We calculated the extent and health status correlates of unobserved Medicare Part D exposure time and examined its association with receipt of beta-blockers. Read More