Factors affecting withdrawal and donation attrition in the brains for dementia research cohort.

Objectives: To measure two forms of attrition in a cohort of volunteer brain donors: Withdrawal during life and non-donation at death. To test whether cognitive impairment independently predicts attrition.

Method: Attrition rates were calculated for all registered participants and for all brain donors who had completed a baseline and follow-up assessment of cognition, health, and lifestyle. Attrition reasons were described, and attrition rates were compared by gender, age group, and cognitive status. Multivariate logistic regression was used to identify the factors which independently predicted during life and at death.

Results: A total of 3276 brain donors registered and 2307 (70.4%) remained in the cohort. Attrition rate overall was 5.9% for withdrawal and 13.8% for donation. Family disagreement and the brain bank not being informed of participant death were the most common reasons for withdrawal and donation attrition. Withdrawal was associated with having cognitive impairment (OR 2.0 95% CI 1.1-3.5), increased age (OR 3.1 95% CI 1.4-6.9), and lower education (OR 1.8 95% CI 1.2-2.8). Participants exhibiting cognitive decline between assessments were more likely to withdraw (OR 4.9 95% CI 1.7-13.6). Participants living alone were almost twice as likely to die without donating (OR 1.9 95% CI 1.1-3.3).

Conclusions: Attrition rates were relatively low, and consistent with other studies cognitive impairment, increased age, and less education predicted study withdrawal. Deaths of participants living alone were less likely to result in donation. Tailored, regular retention practices aimed at resolving family disagreement regarding donation decisions are required.