Instrumental Activities of Daily Living Difficulties Predict Cognitive Decline in Older Puerto Rican Adults

Given the hypothesized bidirectional association between functional and cognitive decline, further characterization of the temporal association between the two is needed, especially in Latinx samples as they are the most rapidly growing demographic in the United States and at greater risk for Alzheimer’s disease. This study assessed bidirectional associations between instrumental activities of daily living (IADL) difficulty and cognition in older Puerto Rican adults. Participants included 2,840 community-dwelling adults (60+ years) without cognitive impairment who completed baseline and a four-year follow-up in the Puerto Rican Elderly: Health Conditions (PREHCO) project. At each wave, cognition (using the Mini-Mental Cabán) and self-reported IADL difficulty (a sum score of 10 everyday tasks) were measured. Covariates included age, gender, education, comorbidities, and depressive symptoms. Bidirectional associations were tested using a path model with concurrent and cross-lagged paths between cognition and IADL difficulty adjusting for covariates. Lower baseline cognition related to more baseline IADL difficulty (B=-0.08, SE=0.02, p<.001). Cognitive decline at follow-up related to greater IADL difficulty at follow-up (B=-0.06, SE=0.02, p=.012). Looking at cross-lagged associations, greater baseline IADL difficulty associated with more cognitive decline at follow-up (B=-0.10, SE=0.04, p=.012). However, baseline cognition was not significantly associated with change in IADL difficulty at follow-up (B=-0.003, SE=0.02, p=.869). Findings support the growing body of literature that IADL difficulties can predict future cognitive decline in samples of community-dwelling older adults. More research into both functional and cognitive decline in Latinx samples will provide a more generalizable view of aging.

Latent Classes of First Incident Difficulty in Instrumental Activities of Daily Living

Ability to perform instrumental activities of daily living (IADLs) deteriorates during prodromal Alzheimer’s disease (AD), eventually leading to impaired everyday functioning and dementia. Ordering and timing of IADL difficulty onset may identify individuals at greater risk of cognitive impairment, but most studies only consider total number of difficult tasks. Leveraging longitudinal data from the Advanced Cognitive Training in Independent and Vital Elderly (ACTIVE) Study who entered free of any IADL difficulty (N=1266), we hypothesized that a latent class analysis based on timing of first reported IADL task difficulty would reveal class differences in cognitive functioning . Participants were followed until they self-reported at least one IADL difficulty, study completion (10 years), or loss to follow-up. Discrete-time multiple event process survival mixture (MEPSUM) models were used to simultaneously estimate hazards of incident IADL task difficulty across 7 task groups. Two, 3, 4, and 5 latent class models were fit to the data. Both unadjusted and covariate-adjusted models (adjusted for age, sex, race, education, marital status, and general health rating) were fit. Using the 2-class solution as the most parsimonious model, model entropy was 0.855. The model was able to distinguish a class of participants with lower global cognitive factor scores at baseline (Cohen’s D = 0.23, P = 0.04). We conclude that first incident IADL difficulty may be a useful measure in identifying individuals with worse cognitive functioning.