Effects of long work hours and poor sleep characteristics on workplace injury among full‐time male employees of small‐ and medium‐scale businesses

Summary The aim of this study was to investigate the effects of long work hours and poor sleep characteristics on workplace injury. A total of 1891 male employees, aged 18–79 years (mean 45 years), in 296 small‐ and medium‐scale businesses in a suburb of Tokyo were surveyed by means of a self‐administered questionnaire during August–December 2002. Work hours and sleep characteristics, including daily sleep hours, subjective sleep sufficiency, sleep quality and easiness to wake up in the morning, were evaluated. Information on workplace injury in the past 1‐year period was self‐reported. The risk of workplace injury associated with work hours and poor sleep was estimated using multivariate logistic regression with odds ratio (ORs) and 95% confidence intervals as measures of associations. Compared with those working 6–8 h day−1 with good sleep characteristics, positive interactive effects for workplace injury were found between long work hours (>8–10 h day−1 or >10 h day−1) and short sleep duration (