Estimating the effect of Pravastatin versus usual care under full adherence in the Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial–Lipid Lowering Trial (ALLHAT-LLT)

This study reanalyzes data from the ALLHAT-LLT randomized trial to estimate the causal effect of pravastatin under full adherence, rather than intention-to-treat assignment. Using methods that adjust for nonadherence, the authors find that while the original trial showed no mortality benefit, full adherence to pravastatin was associated with a reduction in all-cause mortality risk. These findings highlight how treatment adherence can substantially influence estimated effectiveness in clinical trials.