Original ArticlesNIA-Funded Alzheimer Centers Are More Efficient than Commercial Clinical Recruitment Sites for Conducting Secondary Prevention Trials of DementiaEdland, Steven D. PhD* †; Emond, Jennifer A. MS†; Aisen, Paul S. PhD*; Petersen, Ronald C. MD, PhD‡Author Information Departments of *Neurosciences †Family Preventive Medicine, University of California San Diego, La Jolla, CA ‡Department of Neurology, Mayo Clinic College of Medicine, Rochester, MN Supported by the National Institute on Aging grants to the Alzheimer's Disease Cooperative Study (U01 AG010483) and the University of California San Diego Alzheimer's Disease Research Center (P50 AG005131). Reprints: Steven D. Edland, PhD, Department of Neurosciences, University of California San Diego, La Jolla, CA (e-mail: email@example.com). Received for publication July 24, 2009; accepted September 24, 2009 Alzheimer Disease & Associated Disorders: April-June 2010 - Volume 24 - Issue 2 - p 159-164 doi: 10.1097/WAD.0b013e3181c9983f Buy Metrics Abstract Study participant 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 disease (AD) [NEJM 2005;352 (23):79 to 88] to determine predictors of study participant 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 participants, 230 (30%) discontinued prematurely. Risk of dropout was higher among nonwhites [hazard ratio (HR) 2.1, P=0.0007], participants with less than college education (HR=1.6, P=0.02), participants with a Hamilton Depression score of 6 or more (HR=1.3, P=0.04), unmarried males (HR=2.1 relative to married males, P=0.003) and participants recruited by commercial clinical sites (HR=2.2 relative to participants 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 participants 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. © 2010 Lippincott Williams & Wilkins, Inc.