School of Public Health, Epidemiology and Biostatistics, University of California Berkeley, Berkeley, California, USA.
National Technology and Development Program, USDA Forest Service, Missoula, Montana, USA.
Occup Environ Med. 2020 Jul;77(7):433-438. doi: 10.1136/oemed-2019-106186. Epub 2020 Jan 29.
In order to make recommendations to protect wildland firefighters (WLFFs) from heat-related illness, the role physical exertion plays on core body temperature (Tc) in the work environment needs to be considered. We aimed to estimate the association of time-varying job tasks with differing exertion levels on change in Tc, among WLFFs engaged in fire management activities, while controlling for ambient conditions and individual characteristics. In addition, we examined whether duration of tasks modified the relationship between task and change in Tc.
We used data from The Wildland Firefighter Heat Related Illness study, a repeated measures study with individual-level data on 301 WLFFs from 2013 to 2016. Job tasks over one full shift were recorded and categorised into four levels (sedentary, light, moderate and high) based on estimated exertion levels. Tc was measured every 15 s using an ingestible sensor and personal monitors measured ambient conditions. The analysis used generalised estimating equations with an autoregressive correlation structure.
We found statistically significant associations between job tasks with increased physical demand and increases in Tc. When compared with sedentary tasks, the estimated increases in Tc for light, moderate and high activity tasks of average duration were 0.07°C (95% CI 0.02 to 0.11°C), 0.19°C (95% CI 0.15 to 0.23) and 0.44°C (95% CI 0.39 to 0.49°C), respectively. In addition, we found evidence of interaction between task type and duration.
This study supports the hypothesis that occupational exposure to physical exertion increases Tc, highlighting the need to update recommendations to protect WLFFs from heat-related illness.
为了提出保护野外消防员（WLFF）免受与热相关疾病的建议，需要考虑在工作环境中体力活动对核心体温（Tc）的影响。我们旨在估计时间变化的工作任务与不同的用力水平对从事火灾管理活动的 WLFF 的 Tc 变化的关联，同时控制环境条件和个体特征。此外，我们还检查了任务持续时间是否改变了任务与 Tc 变化之间的关系。
我们使用了来自野外消防员热相关疾病研究的数据，这是一项具有个体水平数据的重复测量研究，涉及 2013 年至 2016 年的 301 名 WLFF。根据估计的用力水平，将一个完整轮班的工作任务记录并分类为四个级别（久坐、轻度、中度和高度）。使用可摄入传感器每 15 秒测量一次 Tc，个人监测器测量环境条件。分析采用具有自回归相关结构的广义估计方程。
我们发现，与体力要求增加的工作任务与 Tc 升高之间存在统计学上显著的关联。与久坐任务相比，平均持续时间的轻度、中度和高度活动任务的 Tc 估计增加分别为 0.07°C（95%CI 0.02 至 0.11°C）、0.19°C（95%CI 0.15 至 0.23°C）和 0.44°C（95%CI 0.39 至 0.49°C）。此外，我们发现任务类型和持续时间之间存在交互作用的证据。
这项研究支持了这样的假设，即职业体力活动暴露会增加 Tc，这强调了需要更新建议以保护 WLFF 免受与热相关的疾病。
