Quantifying bias reduction with fixed‐duration versus all‐available covariate assessment periods

Purpose Implementing a cohort study in longitudinal healthcare databases requires looking back over some covariate assessment period (CAP) preceding cohort entry to measure confounders. We used simulations to compare fixed‐duration versus all‐available CAPs for confounder adjustment in the presence of differences in available baseline time between exposure groups. Methods We simulated cohorts of 10 000 patients with binary variables for a single...