Institute of Statistics, National Chiao Tung University, Hsinchu, Taiwan.
Department of Occupational Safety and Health, College of Public Health, China Medical University, Taichung, Taiwan
BMJ Open. 2019 Jul 30;9(7):e028973. doi: 10.1136/bmjopen-2019-028973.
Taiwan revised its criteria for overwork-related cerebrovascular and cardiovascular disease (CCVD) in 2010. A new definition of overwork increased the number of recognised cases. Meanwhile, actual average working hours decreased. We estimated the effects of the revised criteria on the number of overwork-related CCVD cases and the mediation effect through reduced working hours.
From the Labor Insurance of Taiwan, we collected data on the total number of overwork-related CCVD cases from 2006 to 2016 and average monthly working hours for 13 industry groups. We conducted causal mediation analysis to investigate the mechanism of the effect of new criteria on CCVD mediated by working hours.
From 2006 to 2016, 594 overwork-related cases of CCVD were recognised across 13 industry groups. After introducing the new criteria, overwork-related CCVD increased by 8.40 cases (per one million person-years) (95% CI 4.53 to 15.05), which resulted from a decrease of 1.54 (95% CI 0.22 to 3.82) cases due to reduced working hours (mediation effect) and an increase of 9.93 (95% CI 5.24 to 18.17) cases related to the effect of the criteria change and other covariates excluding working hours (alternative effect).
Working hours are an important mediator of the effect of policy on the rate of overwork-related CCVD. Introducing new criteria for recognising overwork-related disease might raise awareness and prompt reductions in working hours, which also help to reduce CCVD. Our findings suggest that understanding mediation effects is important to evaluating national health policies.
台湾于 2010 年修订了与工作相关的脑血管和心血管疾病（CCVD）的标准。新的过度劳累定义增加了已识别病例的数量。与此同时，实际平均工作时间减少了。我们评估了修订标准对与过度劳累相关的 CCVD 病例数量的影响，以及通过减少工作时间产生的中介效应。
我们从台湾的劳保中收集了 2006 年至 2016 年与工作相关的 CCVD 总病例数和 13 个行业组的平均月工作时间的数据。我们进行了因果中介分析，以调查新准则通过工作时间对 CCVD 的影响的机制。
在 13 个行业组中，从 2006 年至 2016 年，共识别出 594 例与工作相关的 CCVD 病例。引入新标准后，与工作相关的 CCVD 增加了 8.40 例（每百万人口年）（95%CI4.53 至 15.05），这是由于工作时间减少导致的减少了 1.54 例（95%CI0.22 至 3.82）（中介效应），以及由于标准变化和工作时间以外的其他协变量（替代效应）导致的增加了 9.93 例（95%CI5.24 至 18.17）。
工作时间是政策对与工作相关的 CCVD 发病率的影响的重要中介因素。引入识别与工作相关的疾病的新标准可能会提高认识并促使减少工作时间，从而有助于减少 CCVD。我们的研究结果表明，了解中介效应对于评估国家卫生政策很重要。
