Heterogeneity of Informant-Reported Functional Performance in Mild Cognitive Impairment: A Latent Profile Analysis of the Functional Activities Questionnaire.

Heterogeneity of subtle functional difficulties in mild cognitive impairment (MCI) remains poorly understood. We characterized patterns of informant reports of functional abilities among participants with MCI and the relation between functional ability pattern and cognitive abilities and subsequent decline. Data from 4,273 MCI participants from the National Alzheimer's Coordinating Center (NACC) Uniform Data Set (UDS) were included in latent profile analyses (LPA) of informant responses on the Functional Activities Questionnaire (FAQ). Profiles from the best fitting model were compared on demographic, clinical, and cognitive variables. The best fitting model supported three profiles varying by level and type of difficulty: intact function (n = 3,299), intermediate (n = 769), and high ratings of difficulty (n = 205). For the Intermediate profile, items related to finances, remembering dates, and travel were rated as most difficult. The High Ratings profile also had elevated ratings on the meal preparation item. Participants with either the Intermediate or High Ratings profile demonstrated a three-fold increase in conversion to dementia as compared to participants with the Intact profile. Demographically, the Intact profile was younger and consisted of a higher proportion of minorities. On cognitive tests, the Intact profile showed the best performance, and the Intermediate profile performed comparably to or better than the High Ratings profile. There is meaningful heterogeneity in informant ratings of function in MCI, though individuals with MCI whose informants report even intermediate-level functional difficulties are more likely to progress to dementia, suggesting that even subtle functional difficulties place individuals at higher risk for future decline.