NIA FUNDED ALZHEIMER CENTERS ARE MORE EFFICIENT THAN COMMERCIAL CLINICAL RECRUITMENT SITES FOR PERFORMING SECONDARY PREVENTION TRIALS OF DEMENTIA

摘要

Study subject dropout compromises clinical trials by reducing statistical power and potentially biasing findings. We use data from a trial of treatments to delay the progression of mild cognitive impairment to Alzheimer’s disease (AD) (NEJM 2005;352(23):79–88) to determine predictors of study subject dropout and inform the design and implementation of future trials. Time to study discontinuation was modeled by proportional hazards regression with censoring at incident dementia or trial completion. Of 769 subjects, 230 (30%) discontinued prematurely. Risk of dropout was higher among nonwhites (hazard ratio (HR) 2.1, p=0.0007), subjects with less than college education (HR=1.6, p=0.02), subjects with a Hamilton Depression score of six or more (HR=1.3, p=0.04), unmarried men (HR=2.1 relative to married men, p=0.003) and subjects recruited by commercial clinical sites (HR=2.2 relative to subjects recruited by NIA funded AD research centers, p<0.0001). A trial using commercial sites with the discontinuation rates and incident dementia event rates experienced in this trial would require 80% more subjects than a comparably powered trial using NIA funded AD research center sites. Targeted retention efforts and utilization of academic sites could substantively improve the statistical power and validity of future clinical trials of cognitively impaired elderly.