Changes in Daily Functioning in Association With Tau and Amyloid Among Unimpaired Older Adults With and Without Elevated Amyloid.

BACKGROUND AND OBJECTIVES

Everyday functioning declines gradually over time in Alzheimer disease (AD), with the earliest changes potentially occurring at the preclinical stage. We investigated how changes in everyday functioning relate to (changes in) amyloid and tau in a large sample of cognitively unimpaired older adults, most of whom had elevated amyloid levels at the start of the study.

METHODS

This prospective study included participants from a 240-week randomized controlled trial of an anti-amyloid drug, solanezumab, and individuals who screen-failed because of a negative amyloid PET scan. A subset (n = 434) underwent repeated tau PET scans. Participants and their study partners completed the Alzheimer's Disease Cooperative Study Activities of Daily Living Prevention Instrument multiple times during the double-blind phase of the trial. Using generalized least-squares models, fit by restricted maximum likelihood, we analyzed how changes in everyday functioning related to amyloid and tau PET. We also correlated changes in amyloid and tau PET with changes in everyday functioning.

RESULTS

A total of 1,707 participants (71.5 ± 4.7 years, 60% female) showed a marginal decline in everyday functioning. Among individuals with elevated amyloid, those with the highest levels of neocortical and medial temporal tau showed the largest decline in everyday functioning, as reported by the participants and their study partners. Increases in neocortical and medial temporal tau correlated moderately (correlation coefficient ranging from -0.2 to -0.5) with a decline in ADCS ADL-PI scores. Functional changes were not evident with amyloid alone. At the item level, participants and their study partners were most likely to report increased difficulty at the last visit with completing complex activities and selecting and paying for items when shopping.

DISCUSSION

Higher tau levels are associated with the fastest decline in everyday functioning in the presence of elevated amyloid, and those accumulating more tau show a faster decline in everyday functioning. These findings demonstrate the utility of including sensitive measures of everyday functioning in clinical practice and clinical trials at the stage of preclinical AD.

TRIAL REGISTRATION INFORMATION

The A4 study, ClinicalTrials.gov ID: NCT02008357; and Longitudinal Evaluation of Amyloid Risk and Neurodegeneration, ClinicalTrials.gov ID: NCT02488720.