Assessment of risk in longitudinal observational studies with time-varying drug exposures for treatment of a chronic disease

Introduction Advancing age, comorbid conditions, and cumulative drug exposures contribute to long-term health outcomes among persons with chronic diseases [1-3]. Historically, observational studies using administrative pharmacy claims characterize drug exposure as either dichotomized variables or as cumulative exposure for drug class, combination regimens, or specific drugs [4]. Measurement bias in prescribed drug exposures measured in administrative