Retention and Compliance.
A total of n = 3,960 subjects were randomized and completed the baseline COSMOS-Web assessment, and n = 3,562 (90.0%) participants completed at least one yearly follow-up cognitive assessment and comprise the intention-to-treat (ITT) analytic sample. The proportion of randomized participants who make up the ITT analytic sample was similar between groups [n = 1,744 of 1,946 (89.6%) in the dietary flavanol group; n = 1,818 of 2,014 (90.3%) in the placebo group]. Completion of follow-up measurements by COSMOS participants for the primary outcome, ModRey, at years 1, 2, and 3 among the ITT analytic sample was 95.2%, 87.3%, and 82.9%, respectively.Pill compliance (not missing >8 d/mo of study pills) based on self-reported pill counts was high among the ITT sample at each year (years 1, 2, and 3: 91.3%, 88%, and 86.7%, respectively) with no significant differences between randomized groups at year 1 (