Longitudinal associations between 24-hour movement behaviours and cognitive function in adults aged 55 and above.

backgroundAge-related cognitive decline poses challenges to healthy ageing. Physical activity (PA), sedentary behaviour (SB) and sleep have been linked to cognition, yet much evidence is cross-sectional and fails to account for the interdependent nature of these 24-h movement behaviours. This observational study applied a compositional approach to investigate longitudinal associations between 24-h movement behaviours and cognition in cognitively healthy adults.

methodsCommunity-dwelling adults aged ≥ 55 years were assessed at three time points, each one year apart (baseline n = 233; 51.1% women; mean age 68.3 ± 7.7 years). Each time, 7-day wrist-worn accelerometery data (ActiGraph wGT3X-BT) were acquired and processed with GGIR to derive time spent in PA, SB and sleep. Additionally, cognition was measured using the Cambridge Neuropsychological Test Automated Battery (CANTAB), yielding composite z‑scores for short‑term memory (STM), long‑term memory (LTM), executive function (EF) and processing speed (PS). Linear mixed-effects models tested longitudinal associations between time-varying time-use composition (i.e. 24-h movement behaviours expressed as isometric log-ratios) and cognition. Time was modelled as a categorical variable and models included an interaction between time-use composition and time. Analyses were adjusted for sociodemographic and health covariates. Exploratory post‑hoc compositional isotemporal substitution analyses estimated cognitive differences associated with hypothetical time reallocations between behaviours at each time point.

resultsNo significant associations were observed between time-use composition and STM, LTM or PS. After adjusting for age, sex, educational level and living arrangement, EF was significantly associated with time-use composition (p = 0.005) and time (p < 0.001), with no significant interaction effect, suggesting a stable relationship over time. Exploratory post-hoc analyses suggested that moderate-to-vigorous PA (MVPA) was the primary driver of the EF association. Descriptive reallocation patterns at each time point indicated that reallocating time towards MVPA (e.g. from light PA) was generally associated with higher EF scores, whereas reallocations away from MVPA were associated with lower EF scores.

conclusionsIn adults aged ≥ 55, 24‑h movement behaviours were associated with EF but not memory or PS, and these associations remained stable over time. Future research should examine longer follow-up periods, the (cognitive) context of behaviours and how changes in time-use composition relate to changes in cognition.