Importance of home study visit capacity in dementia studies

INTRODUCTION: The importance of home research study visit capacity in Alzheimer's disease (AD) studies is unknown. METHODS: All evaluations are from the prospective Adult Changes in Thought study. Based on analyses of factors associated with volunteering for a new in-clinic initiative, we analyzed AD risk factors and the relevance of neuropathologic findings for dementia comparing all data including home visits, and in-clinic data only. We performed bootstrapping to determine whether differences were greater than expected by chance. RESULTS: Of the 1781 people enrolled during 1994-1996 with ≥1 follow-up, 1369 (77%) had in-clinic data, covering 61% of follow-up time. In-clinic data resulted in excluding 76% of incident dementia and AD cases. AD risk factors and the relevance of neuropathologic findings for dementia were both different with in-clinic data. DISCUSSION: Limiting data collection in AD studies to research clinics alone likely reduces power and also can lead to erroneous inferences.