Predictors of Retention in the 1Florida Alzheimer's Disease Research Center (ADRC) Over Two Waves.

Attrition is a significant methodological concern in longitudinal studies. Sample loss can limit generalizability and compromise internal validity. Wave one ( = 346) and wave two follow-ups ( = 196) of the 1Florida ADRC clinical core were examined using a 24-month visit window. The sample (59% Hispanic) demonstrated retention rates of 77.2% and 86.2% in waves one and two, respectively. Predictors of lower retention in wave one included older age, amnestic MCI or dementia, and lower cognition and function scores. Completing a baseline MRI and lack of hippocampal atrophy were associated with higher retention in both waves. In wave two, a greater neighborhood disadvantage score was associated with attrition. Predictors of retention changed over time, possibly due to the early withdrawal of the most vulnerable in the initial wave. Understanding predictors of retention can facilitate retention strategies, reduce attrition, and increase the validity of findings.