Job strain and sleep quality in Japanese civil servants with special reference to sense of coherence

The combination of poor sleep quality and high job strain may provoke poor health status. Meanwhile, a sense of coherence (SOC), composed of comprehensibility, manageability and meaningfulness has been associated with adoptive measures in responding to life stress. In this study we investigated the impact of job strain on the sleep quality in civil servants and the extent to which SOC affects their sleep quality. In this cross-sectional study we evaluated 1682 civil servants working in departments related to the municipality of T city in Toyama prefecture, Japan, in the spring of 2001. Using the validated Japanese versions of Pittsburgh sleep quality index (PSQI-J), SOC-13 and a self-reported questionnaire providing information on psychosocial stress in the workplace, we conducted logistic regression analysis to assess the impact of low and high SOC (differentiating by the median score) on sleep quality in different levels of job strain. Using a cut-off point of 5.5 in the PSQI-J global score, high job strain subjects were less likely to have good sleep quality (Odds ratio=0.62; 95% confidence interval: 0.44-0.86) compared with those with lower levels of strain at the workplace after adjusting for potential confounders. Compared with high job strain/low SOC subjects, high job strain/high SOC civil servants were likely to have better sleep quality (Odds ratio=2.12; 95%CI: 1.08-4.19) after adjusting for age, sex, employment category, level of education and negative affectivity. Increasing psychological stress at the workplace may decrease sleep quality in Japanese civil servants, but a high sense of coherence may attenuate the adverse impact of job strain on sleep quality.