Sleep duration, sleep-wake schedules, and social jetlag among corporate employees in Japan: Age- and gender-based comparisons of wearable device data (2019-2022).

OBJECTIVES

Insufficient sleep has been linked to cardiovascular events and mortality, yet most prior studies rely on self-reported sleep duration. Large-scale longitudinal studies based on objective sleep measurements remain scarce. This study aimed to describe 3-year sleep-wake patterns, including total sleep time (TST) and social jetlag, using data from a validated wearable device (Fitbit), and to compare these patterns by gender, age, weekday versus weekend, and fiscal year.

METHODS

The study included 20,886 corporate employees insured by Japanese health insurance associations with JMDC Inc. A total of 10,670 participants complete data contributed 5,156,835 sleep observations. Gender differences in weekday and weekend sleep were assessed using t-tests. Pairwise comparisons were conducted to estimate mean differences across age groups by gender. The chi-squared test was used to compare categorical measures of social jetlag.

RESULTS

Mean TST was 5.84 ( ± 0.66) hours. Social jetlag of 1-2 and ≥ 2 h were observed in 21.7% and 3.1% of participants, respectively. Across all age groups and sexes, TST was 0.5-1.0 h shorter on weekdays than on weekends. Women exhibited greater social jetlag than men.

CONCLUSIONS

This study demonstrates that objectively measured TST among Japanese is shorter than self-reported estimates and varies by age and gender.