Predictive factors of attrition in a cohort of Alzheimer disease patients

Background: Attrition, i.e. patient dropout, can threaten the validity of results in longitudinal studies. The aim of this study was to identify patient and caregiver factors predictive of attrition in a cohort of Alzheimer disease (AD) patients. Methods: 686 patients with mild to moderate AD were included in the multicenter prospective REAL.FR study. Standardized gerontological evaluations were carried out twice yearly. Factors associated with attrition were assessed by survival analysis using a Cox proportional hazard model. Results: After 2 years, 278 (40.5%) patients had dropped out. Causes of attrition included refusal (20.9%), death (20.1%), institutionalization (19.8%), and loss to follow-up (19.8%). Attrition rates between each 6-month wave were constant at 12%. After adjustment, several independent factors remained associated with attrition: patients cared for by an unrelated caregiver [HR 1.7; 95% CI (1.08-2.59)], loss of autonomy [HR = 1.37; (1.03-1.82)], increasing caregiver burden [HR = 1.014; (1.005-1.022)], use of cholinesterase inhibitors [HR = 0.40; (0.27-0.59)], use of 1 to 3 other types of medication [HR = 0.57; (0.36-0.89)]. Conclusions: The identification of both patient and caregiver factors predictive of attrition is of particular interest for the development and targeting of attrition prevention strategies. In patients with chronic diseases, particular attention should be paid to caregiver wellbeing to limit attrition. Copyright (C) 2008 S. Karger AG, Basel.