Watanabe Kazuhiro, Yokoyama Kazuhito, Tsutsumi Akizumi
Department of Public Health, Kitasato University School of Medicine, 1-15-1 Kitazato, Minami-ku, Sagamihara 252-0374, Japan.
Department of Epidemiology and Social Medicine, Graduate School of Public Health, International University of Health and Welfare, 4-1-26 Akasaka, Minato-ku, Tokyo 107-8402, Japan.
J Occup Health. 2025 Jan 7;67(1). doi: 10.1093/joccuh/uiaf032.
Limited empirical data are available regarding the safety of self-employed workers in Japan. This study investigated the associations between working hours, income, and work-related injuries among freelancers.
A cross-sectional study was conducted using data from an internet survey conducted in 2022. Self-employed individuals who did not work as employees or earn an income from their employment were recruited. Work-related injuries, working hours, and annual income were assessed using self-reported questionnaires. Prevalence ratios (PRs) of injury were estimated using modified Poisson regression models, while controlling for covariates. Additionally, PRs were analyzed for each stratum of working hours and income levels.
In total, 1856 freelancers met the eligibility criteria and were included in the study. Among them, 222 (12.0%) experienced at least 1 work-related injury. A significantly higher risk of injury was observed among those working long hours (≥60 h/wk: PR = 1.65; 95% CI, 1.16-2.34; P = .005) and those in the second-lowest income bracket (¥2 to <¥4 million: PR = 1.43; 95% CI, 1.05-1.94; P = .024). Furthermore, several strata exhibited significantly higher PRs, particularly among workers with high incomes who also worked long hours (≥60 h/wk).
Long working hours, particularly exceeding 60 h/wk, are associated with a significantly higher risk of work-related injuries among freelancers. Additionally, 2 high-risk groups were identified based on the combination of working hours and income levels: those with relatively low incomes, and high-income earners who also worked extended hours.
关于日本个体经营者的安全性，现有的实证数据有限。本研究调查了自由职业者的工作时长、收入与工伤之间的关联。
采用2022年进行的一项网络调查数据开展横断面研究。招募未受雇工作或未从受雇工作中获得收入的个体经营者。使用自我报告问卷评估工伤、工作时长和年收入。在控制协变量的同时，使用修正泊松回归模型估计受伤的患病率比（PRs）。此外，还对工作时长和收入水平的每个分层进行了PRs分析。
共有1856名自由职业者符合纳入标准并被纳入研究。其中，222人（12.0%）经历过至少一次工伤。长时间工作（≥60小时/周：PR = 1.65；95%置信区间，1.16 - 2.34；P = 0.005）以及处于第二低收入组（200万日元至<400万日元：PR = 1.43；95%置信区间，1.05 - 1.94；P = 0.024）的人群中，受伤风险显著更高。此外，几个分层的PRs显著更高，尤其是在高收入且长时间工作（≥60小时/周）的工作者中。
长时间工作，尤其是每周超过60小时，与自由职业者工伤风险显著升高相关。此外，根据工作时长和收入水平的组合确定了两个高风险群体：收入相对较低者，以及高收入且工作时间较长者。
