Bidirectional association between physical activity and sleep in healthy Japanese super-seniors: the Japan Healthy Aging Study (J-HAS).

To address the challenges of an ageing population, it is important to promote health by identifying factors for healthy ageing. The aim of this study was to investigate the bidirectional association between physical activity (PA) and sleep in healthy Japanese super-seniors over the age of 80. For approximately 1 year, 124 participants wore wearable devices and answered daily lifestyle questionnaires. PA was defined as daily step count and minutes in light activity. Sleep was measured using 24-h total sleep time (TST) and time in bed (TIB). Associations were analysed bidirectionally using multilevel mixed-effects linear regression models. Fully adjusted models revealed significant and inverse associations between sleep and PA from the same 24-h period. Similarly, the results were significant and inverse with PA from the day before as exposure and the next 24-h sleep measures as outcome. The between-individual associations between sleep measures and PA from the subsequent day were significant and inverse. However, there was a positive within-individual association between TST and step count from the subsequent day. The study suggests that associations between PA and sleep in super-seniors differ from patterns previously described in younger adults. Very old individuals with increasing 24-h total sleep time may compensate for a lower step count on one day by increasing their step count the following day.