LAUSR

Objectives: Although several studies have shown the association between smoking and occupational injury, the exact mechanism by which smoking contributes to occupational injury remains unclear. We conducted a 5-year case–control study in a population of Japanese large-scale enterprise workers aimed to verify the hypothesis that nicotine dependency is positively associated with occupational injury. Methods: A total of 3179 to 3574 male workers annually participated in this study conducted from 2008 to 2012. Employees who had an occupational injury as detailed in the company records were included in the case group, while employees who did not have any occupational injury were included in the control group. Information on smoking status, nicotine dependency [assessed according to time to first cigarette (TTF) and cigarette per day (CPD)], and potential confounders were obtained via questionnaires administered during periodic health checkups. Odds ratios (ORs) were estimated via multiple logistic regression analysis and integrated using the general variance-based fixed effects model. Results: The overall adjusted OR of occupational injury in smokers was 1.71 [95% confidence interval (95% CI): 1.10 to 2.66]. The OR for low and high nicotine dependency according to TTF was 1.52 (95% CI: 0.92 to 2.51) and 1.98 (95% CI: 1.15 to 3.41), respectively. Conclusion: Nicotine dependency was related to an increased risk of occupational injury. These findings support the hypothesis that smoking is associated with occupational injury.