Daily Movement Activities Are Associated With Within-Person Instability of Cognitive Function in Older Adults: Evidence From an Ambulatory Assessment Study.

Background and objectives: Physical inactivity and excessive sedentary time (ST) are associated with poor cognitive health in older adults. However, current literature largely relies on cross-sectional designs or in-lab cognitive assessments, which do not adequately reflect cognitive function in naturalistic settings. Further, existing studies have largely overlooked the variability or the instability in daily cognitive function, which represents a critical marker of cognitive decline. This ambulatory assessment study examined the temporal associations of daily movement behaviors with the mean levels and the variability of cognition among older adults at risk of dementia.

Research design and methods: 96 older adults from the community (68.3 ± 7.1 years) participated in this 14-day study. They wore an accelerometer and completed smartphone-based cognitive tests up to 4 times per day. The cognitive tests assessed both performance-based and subjective cognition. The movement behaviors collected from the accelerometers include daily light-intensity physical activity (LPA), moderate-to-vigorous physical activity (MVPA), and ST. Mixed-effects location-scale models were applied to estimate the within- and between-person associations of movement behaviors and cognitive outcomes in terms of the mean levels and the degree of variability. A total of 1,269 day-level observations were analyzed.

Results: Older adults' between-person levels of daily MVPA and steps were associated with better mean cognitive performance and lower variability across cognitive measures. Older adults' daily LPA was positively associated with subjective cognition in both mean levels and variability. The increases in within-person levels of ST were negatively associated with older adults' variability of all cognitive outcomes.

Discussion and implications: Study results suggest that moving more and sitting less in day-to-day life may sustain proximal cognitive health. Applying ambulatory assessments can advance aging research by examining the temporal dynamics between daily movement activities and within-person variability of cognition to inform strategies for promoting healthy aging in daily life.