Objective: To explore the associations of temperature, relative humidity, and their interaction effect with fall risk. Methods: Data on fall cases were collected using the national injury surveillance system from May to September, in 2006-2022 in Hubei Province. Combined with the meteorological and air pollution data, we conducted a time-stratified case-crossover design and used conditional logistic regression models and distributed lag nonlinear models to examine the exposure-response relationships between temperature, humidity, and fall risk. We further divided the low and the high temperature groups and the low and the high relative humidity groups and analyzed the excess risk (ER) of falls attributed to dry-hot or wet-hot events. Finally, we calculated the additive interactions of temperature and humidity on fall risk. Results: A total of 55 401 fall cases were included. With the increase in temperature and relative humidity decrease, the exposure-response curves of fall showed nonlinear upward trends among all populations. Gender and age differences were found in temperature-fall and relative humidity-fall risk relationships. Compared with wet-non-hot (normal temperature and high relative humidity) events, the ER of fall in dry-hot (high temperature and low relative humidity) events was 14.80% (95%CI: 9.69%- 20.15%), and the ER of wet-hot (high temperature and high relative humidity) events was 9.59% (95%CI: 2.52%-17.13%). However, there was no statistically significant difference between dry-hot and wet-hot events in the fall, and no statistically significant difference between different genders, ages, occupations, and fall occurred place (all P>0.05). No significant synergistic additive interaction was found between temperature and relative humidity on fall risk (relative excess risk due to interaction=-0.08, 95%CI: -0.19-0.02). Conclusions: Higher temperatures and lower relative humidity were associated with increased fall risk. Both dry-hot and wet-hot events had a higher risk of fall, while high temperature and low humidity have no synergistic effect on fall risk.
目的： 探究气温、相对湿度及其交互作用对跌倒发生的影响。 方法： 利用全国伤害监测系统收集2006-2022年每年5-9月湖北省跌倒病例，结合气象与空气污染数据，采用时间分层病例交叉设计，通过条件logistic回归模型结合分布滞后非线性模型分析气温、相对湿度与跌倒发生的暴露-反应关系。进一步划分低温组和高温组、低相对湿度组和高相对湿度组，分析干热、湿热复合条件导致跌倒发生的超额风险（ER）。最后，采用相加交互作用模型分析气温与相对湿度的交互作用。 结果： 共收集跌倒病例55 401例。随着气温升高、相对湿度降低，总人群跌倒发生的暴露-反应曲线呈非线性上升趋势，不同性别、年龄人群的暴露-反应曲线存在差异。与湿常温（正常气温和高相对湿度）条件相比，干热（高温和低相对湿度）条件中总人群跌倒发生的ER值为14.80%（95%CI：9.69%~20.15%），湿热（高温和高相对湿度）条件中总人群跌倒发生的ER值为9.59%（95%CI：2.52%~17.13%），但差异无统计学意义，不同性别、年龄、职业、伤害发生地点的亚组人群的差异也无统计学意义（均P>0.05）。气温与相对湿度对跌倒发生的影响无相加交互作用（RERI=-0.08，95%CI：-0.19~0.02）。 结论： 气温升高、相对湿度降低与跌倒发生风险上升相关。干热和湿热条件使得跌倒发生风险均明显上升，但高温和低湿对跌倒发生不具有协同作用。.