• trial attrition;
  • Alzheimer's disease;
  • Parkinson's disease;
  • caregivers


Participant attrition in randomized trials can reduce statistical power and bias outcomes. However, elective withdrawals are seldom discussed in trial reports. We examined factors associated with elective withdrawals for the first 131 Alzheimer's disease (AD) and Parkinson's disease (PD) caregiver participants that entered Project ASSIST (Assistance, Support and Self-health Initiated through Skill Training), an on-going trial of caregiver skill training interventions. After 20 months of recruitment, 14 (11%) of the 131 ASSIST participants had electively withdrawn before completing the final assessment. Survival analysis demonstrated AD caregivers and non-spousal caregivers dropped out earlier than PD and spousal caregivers, even after controlling for selected baseline covariates. Findings suggest caregiver trial contact strategies may need to be tailored to retain different caregiver groups. © 2006 Wiley Periodicals, Inc. Res Nurs Health 29: 498–506, 2006