Association between 24-h time-use composition and brain age: The IGNITE study

The relationships between 24-h time-use composition (i.e., sleep, sedentary behavior, light physical activity, and moderate-to-vigorous physical activity [MVPA]) and brain morphology in older adulthood remain poorly understood. We examined associations between 24-h time-use composition and brain age using compositional data analysis, predicting that 24-h time use would be associated with brain age and that a greater amount of time engaged in MVPA would drive associations with younger brain age.

Baseline data from the Investigating Gains in Neurocognition in an Intervention Trial of Exercise (IGNITE; n = 648) were analyzed. Brain age was estimated using T1-weighted magnetic resonance imaging data. Time-use composition was derived from wrist-worn triaxial accelerometers. Regression models examined associations between 24-h time-use composition (expressed as isometric log ratios) and brain age, adjusting for age, sex, apolipoprotein E4 (APOE4) carriage, education, body mass index, image quality, and site. Compositional isotemporal substitution evaluated how hypothetical reallocations of time between behaviors related to brain age.

The final sample included 573 adults (69.8±3.7 years, 407 females). It was found that 24-h time-use composition was associated with brain age (F = 2.72, p = 0.004). Post hoc modeling indicated that time spent in MVPA primarily drove these associations, such that less MVPA was associated with greater brain age, irrespective of whether time was taken from sleep, sedentary behavior, or light physical activity.

These results suggest that 24-h time use, especially time spent in MVPA, relates to structural brain age in late adulthood. Maintaining or increasing MVPA may help preserve younger brain age, irrespective of which behaviors this time was reallocated from. Future research should examine whether systematically shifting 24-h time use toward MVPA alters brain aging trajectories.Clinical Trial Registration Number and Name of Trial Registry: ClinicalTrial.gov: NCT02875301.

Time use relates to brain age in older adults.More time spent in MVPA may contribute to younger brain age.Associations between time use and brain age are independent of demographic variation or genetic risk for AD.