Work is associated with a more robust rest-activity rhythm and high-intensity physical activity among older adults

Background Work participation is a major element of active aging in aging societies. However, the impact of work on physical activity and rest-activity rhythm has not been well-studied in the older population. Aims To investigate the association of work status with the distribution of physical activity and rest-activity rhythm. Methods The study recruited 35 working and 72 non-working community-dwelling adults older than 60 years old. Biological rhythm was evaluated by dim light melatonin onset (DLMO). Activity distribution and rest-activity rhythm indicators were derived from 14-day actigraphy data, and differences between working and non-working groups were analyzed. The association of activity distribution and rest-activity rhythm indicators with mood symptom was examined. Results Compared to non-working older adults, those who were working exhibited an earlier wake-up time (05:24 h vs. 06:11 h, p = 0.001) and higher levels of daytime activity (most active 10-hour activity count: 25605 vs. 16838, p < 0.001), but similar DLMO (20:20 h vs. 20:24 h, p = 0.914). Work is associated with a more robust rest-activity rhythm as assessed by interdaily stability (beta = 0.18, p < 0.001) and autocorrelation coefficients (beta = 0.09, p = 0.002). Regarding activity distribution, work is associated with high-intensity activity in shorter bouts, as shown by a lower Gini index (beta = -0.04, p = 0.003) and a higher intensity gradient (beta = 0.54, p < 0.001). Conclusions Working and non-working older adults showed similar biological circadian rhythms, but working ones had a more robust rest-activity rhythm and higher levels and intensity of physical activity.