This study examined the effects of work-related behaviors (checking e-mails and overtime work at home) during off-job time on workers’ sleep quality, fatigue, and functional impairment at work in the context of improving the workplace environment (IWE). A manufacturing company conducted the IWE, and 36 workers participated in surveys conducted one month before and 3, 6, and 12 months after the IWE. The survey contained questions about demographic data, sleep quality, psychological detachment during off-job time, fatigue, functional impairment at work, and checking e-mail and overtime work at home during off-job time. Results revealed that functional impairment at work significantly deteriorated 3 months after compared with that one month before the IWE for only the workers engaging in overtime work at home, and they had significant severe functional impairment at work at 3, 6, and 12 months after, compared with the workers who did not engage in overtime work at home. Additionally, IWE significantly improved sleep quality and tended to improve fatigue. The checking e-mail had low psychological detachment, but those engaging in overtime work at home had not only low psychological detachment but also significant severe fatigue and tended to have poor sleep quality, compared to workers not engaging in these behaviors. These results suggest that work-related behaviors during off-job time affects functional impairment at work in the context of IWE. Therefore the work and rest style during off-job time may be key targets for IWE.
