Work e-mail after hours and off-job duration and their association with psychological detachment, actigraphic sleep, and saliva cortisol: A 1-month observational study for information technology employees.

Objective A sufficient duration of time off after work is necessary to ensure workers' health. Better quality of off-job time can also facilitate recovery from fatigue, but its quantitative influence is largely unknown. We aimed to examine how off-job time quality (as measured by the frequency of emailing after work), and off-job duration is associated with psychological detachment, actigraphic sleep, and saliva cortisol using a 1-month observational study. Methods The participants were 58 daytime employees working at an information technology company. Sleep actigraphy and saliva cortisol as well as self-reported outcomes were repeatedly measured for 1 month. Two-way (work e-mail frequency × off-job time) multilevel mixed-effects linear regression analyses were performed in both continuous and categorical variables. Results The frequency of work e-mailing after hours was significantly associated with self-reported outcomes and actigraphic sleep quality, while a significant association was not found in cortisol awakening responses and actigraphic sleep duration. A significantly larger cortisol response after awakening was found in shorter, rather than longer, durations of off-job time. Self-reported detachment, rumination and carry-over fatigue showed significant interactions between work e-mail and off-job time, suggesting that worse outcomes were found in a higher frequency of work e-mail even when employees had longer amounts of off-job time. Conclusion Our findings suggest that ensuring the quality and duration of off-job time is beneficial for recovery from work with sufficient sleep. Specifically, the frequency of e-mailing after work should be minimized to make recovery complete.