Limitations
REGRESSION
This analysis has some important limitations similar to the last follow-up report. First, participants may have stopped the randomization drug once they were unblinded. The unblinding also may have lead to biases. Second, we were not able to conduct a passive outcome ascertainment for all ALLHAT participants due to data availability (Canadian participants were omitted from mortality and combined mortality and morbidity analyses, and VA participants and those without a Medicare number were omitted from the combined mortality or morbidity analyses), resulting in a reduced sample size. Therefore, the individuals in the morbidity and mortality cohorts may not be representative of the general population. However, there were no noted significant differences in the measured baseline demographic distribution for this cohort compared with the full study. Third, posttrial antihypertensive medication use is unknown between study completion (2002) and 2006, and crossover or regression to more similar medications is possible, which could dilute the original treatment distinctions among the 3 randomization groups. A previous study examined posttrial antihypertensive medications based on Medicare Part D–linked data from 2007 and found significant mixing of antihypertensive classes.