The way to healthy telework: Sleep and sleep rhythm changes as the key factors for maintaining mental health and work productivity.

The COVID-19 pandemic and recent advancements in technology have significantly altered workstyles, notably increasing the prevalence of telework. However, it is unclear how telework affects workers' sleep, sleep-wake rhythm, and occupational health outcomes. This longitudinal study aimed to determine the effects of telework and its environment on sleep and circadian rhythms, as well as their impact on psychosomatic stress reactions and presenteeism. This is a multi-workplace cohort study involving 23 companies. Among a total of 6855 full-time workers, 3123 who had not teleworked in 2019 (before the pandemic) and could be followed up in 2020 were targeted for the analyses. The study assessed sleep disturbance using the Pittsburgh Sleep Quality Index, habitual sleep schedules, sleep hygiene, psychosomatic stress reactions measured with the Brief Job Stress Questionnaire, and presenteeism assessed through the Work Limitations Questionnaire. A total of 1683 participants (53.9%) began teleworking in 2020. Telework was associated with delayed sleep schedules and longer overall sleep duration. These factors contributed to both the worsening and the improvement of sleep disturbances, and ultimately offset each other. Sleep disturbance itself was associated with psychosomatic stress reactions and presenteeism. Participants who secured morning light exposure and avoided using electronic displays in bed at night did not exhibit negative changes in their sleep, and their psychosomatic stress reactions and work productivity also improved under telework conditions. Telework had both favorable and unfavorable effects on sleep. Securing sleep duration, maintaining the sleep-wake cycle, and ensuring appropriate sleep hygiene, particularly by securing morning light exposure and avoiding electric light at night, will play important roles in maintaining occupational health and productivity in telework.