Night work as a stressor: The role of sleep reactivity to stress in the relationship between night work and insomnia.

Sleep reactivity to stress is a predisposition to experience sleep disturbances in response to stress. The present study aimed to examine the potential moderating role of sleep reactivity to stress in the relationship between the number of night shifts per month as a stressor and insomnia symptoms. A total of 188 shift-working physicians completed a short questionnaire about work schedule, the Ford Insomnia Response to Stress and the Insomnia Severity Index. Sleep reactivity to stress was a significant moderator of the effect of number of nights worked in the last month on insomnia symptoms. At low and medium sleep reactivity to stress the relationship between the number of night shifts per month and insomnia symptoms was positive and significant. At high sleep reactivity to stress the relationship was no longer significant. The results show that with low and medium sleep reactivity to stress, the more night shifts a person works per month, the more severe insomnia symptoms they will report. With high sleep reactivity to stress even a low number of night shifts per month will lead to a deterioration of sleep. This is important for identifying those who are more vulnerable to adverse consequences of working in the shift system, and the knowledge of workers' sleep reactivity to stress may help in providing targeted interventions.