Not just how much, but how it’s done: movement activity bout distributions and everyday cognition in older adults with elevated dementia risk

Physical activity (PA) is a protective factor of brain health. Existing literature has predominately examined total PA volume or sedentary time in relation to cognitive health, with limited attention to the distributional features of the movement activity bouts. Variability in the duration of daily movement activity bouts may influence cognitive function beyond total exposure to PA or sedentary time. This study investigates whether daily PA and sedentary bout distributions are associated with daily cognitive function in older adults, and further explores whether these associations differ across the days of the week. Older adults (n = 87, age = 68.5 ± 7.0 years, 38% male, 21% non-White) with elevated dementia risk completed 14 days of ecological momentary assessment (EMA). Participants wore an accelerometer (activPAL) and completed smartphone-based cognitive assessments of processing speed four times each day. The number and duration of sedentary, light (LPA), or moderate-to-vigorous physical activity (MVPA) bouts (≥ 1 min) were calculated from the activPAL data. Median response time (RT) and number of correct trials from the symbol search task were aggregated at the day level. Two distributional indicators (alpha and Gini) were each calculated for daily sedentary, LPA, and MVPA bouts to investigate their associations with the symbol search outcomes. Functional regression models examined the associations between the distributional indicators and cognitive outcomes by each day of the week (Sunday-Saturday). On most weekdays, higher Gini (greater variations) in daily MVPA bout length was associated with faster RT (p<.001, R2=0.138); higher Gini of daily LPA bout length was also associated with more accurate trials (p<.05, R2=0.022). Conversely, higher Gini in daily sedentary bout length was associated with slower RT (p<.05, R2=0.164). This study provides proof-of-concept that the distribution of daily movement behavior bouts is associated with variations in daily cognition. It also illustrates how integrating accelerometry with repeated ambulatory cognitive measures can capture within-person dynamics. The findings can support future research to examine whether specific daily movement patterns may represent appropriate targets for interventions aimed at promoting cognitive health in older adults.