Cross‐sectional associations between use of time and cognition in healthy older adults

Abstract

AbstractBackgroundPhysical activity, sedentary behaviour and sleep are independently associated with cognition in older adults. These time‐use behaviours are not independent, rather, co‐dependent parts of the 24‐hour day. As such, spending more time in one leaves less time for the others. The balance of the three time‐use behaviours in the 24‐hour day (or time‐use composition) should be considered to inform 24‐hour movement guidelines for cognition and dementia risk reduction in older populations. Using a compositional data analysis approach, we investigated the associations between time use and cognition in a sample of healthy older adults.Method347 participants (age 60‐70 years; 68% female) took part in this study. 7 days of 24‐hour time use (time spent in sleep, sedentary behaviour, light and moderate‐vigorous physical activity) were captured using accelerometry. Cognition was measured using Addenbrooke’s Cognitive Examination III (global cognition) and computerized CANTAB tests measuring memory, executive function, fluid reasoning and processing speed.Cognitive outcomes were regressed on isometric log ratios (ilrs) of the time‐use compositions, while adjusting for age and sex demographics, to explore potential associations between cognition and time‐use behaviours. For each outcome, four sets of ilr‐coordinate systems were constructed, each with a different time‐use behaviour as the numerator of a log ratio to the mean of remaining time‐use behaviours. The regression coefficient of the first ilr‐coordinate in each of the four ilr systems therefore represented the association between increasing time in the first behaviour relative to all remaining behaviours.ResultAge was negatively associated with performance on memory, executive function, fluid reasoning and processing speed tests. More time in SB at the equal expense of all other behaviours was associated with better memory (β = 0.65, p<.01), whilst spending more time in sleep was associated with poorer memory (β = ‐0.63, p = .02). Spending more time in moderate‐vigorous physical activity was associated with better processing speed (β = 0.25, p = .01).ConclusionHow older adults use their time is associated with cognition. Findings suggest that moving towards a holistic understanding of time use is important to inform future dementia prevention strategies.