Shift work and risk of occupational, transport and leisure-time injury. A register-based case-crossover study of Danish hospital workers

Introduction Shift work has been associated with sleepiness. Sleepiness from shift work may increase the risk of occupational injuries, but could also continue outside of work and increase risk of injury during commuting and leisure time. In this study, we assessed the associations between evening shifts, night shifts and quick returns, and risk of occupational, transport and leisure-time injuries. Material and method We used a case-crossover design to compare characteristics of the shift right before an injury with shifts in previous control periods (i.e. without an injury) within the same individual. Shift information was derived from the Danish Working Hour Database (DWHD) and linked to information on injuries from The National Patient Register. The study populations included a total of 13 337 occupational injuries, 2722 transport injuries and 9768 leisure-time injuries. Data were analysed by conditional logistic regression. Results In the adjusted analyses, the odds of an occupational injury were higher during evening compared with day shifts (OR 1.54, 95%CI 1.43–1.66) and quick returns compared with regular returns (OR 1.26, 95%CI 1.10–1.44). No higher odds of a leisure-time injury or leisure time transport injury were observed after evening shift or night shifts vs. day shifts, or quick returns vs. regular returns. Conclusion Our findings support the evidence of a higher risk of occupational injuries during evening shifts and after quick returns. Findings on leisure-time transport and commuting injuries were inconclusive, while we found no support for a higher risk of injury during leisure-time after evening shifts, night shifts or quick returns.