24-Hour time use and cognitive performance in late adulthood: results from the Investigating Gains in Neurocognition in an Intervention Trial of Exercise (IGNITE) study.

Objective: This cross-sectional study examined associations between 24-hour time-use composition (i.e. sleep, sedentary time, light physical activity and moderate-to-vigorous physical activity) and cognitive performance and explored whether demographic or genetic factors moderated these relationships.

Methods: This analysis included baseline data from cognitively unimpaired older adults (n = 648) enrolled in the Investigating Gains in Neurocognition in an Intervention Trial of Exercise study. Time use was measured using wrist-worn triaxial accelerometers. Cognitive domains were determined using a confirmatory factor analysis from a comprehensive neuropsychological battery. Linear regression models tested associations between time-use composition and cognitive factors, adjusting for age, sex, education, body mass index, apolipoprotein E4 (APOE4) allele carriage and study site. Interaction terms evaluated moderation of time use by age, sex, education and APOE4 status. We also examined the theoretical impact of reallocating time between time-use behaviours on cognitive performance using compositional isotemporal substitution methods.

Results: Time-use composition was associated with processing speed (F = 5.16, P = .002), working memory (F = 4.81, P = .003) and executive function/attentional control (F = 7.09, P < .001) but not episodic memory (F = 2.28, P = .078) or visuospatial function (F = 2.26, P = .081). Post hoc isotemporal substitution analyses found that significant associations were driven by time spent in moderate-to-vigorous physical activity (MVPA), with lesser amounts of MVPA associated with poorer cognitive performance. There was no evidence of moderation by any tested factors.

Conclusions: Increasing or decreasing MVPA, at the expense of time spent in sleep, sedentary behaviour or light physical activity, may be related to individual variation in processing speed, executive function/attentional control and working memory in older adulthood.