Abstract

Background:

Although substantial evidence suggests that high and low temperatures are adversely associated with nonaccidental mortality, few studies have focused on exploring the risks of temperature on external causes of death.

Objectives:

We investigated the short-term associations between temperature and external causes of death and four specific categories (suicide, transport, falls, and drowning) in 47 prefectures of Japan from 1979 to 2015.

Methods:

We conducted a two-stage meta-regression analysis. First, we performed time-stratified case-crossover analyses with a distributed lag nonlinear model to examine the association between temperature and mortality due to external causes for each prefecture. We then used a multivariate meta-regression model to combine the association estimates across all prefectures in Japan. In addition, we performed stratified analyses for the associations by sex and age.

Results:

A total of 2,416,707 external causes of death were included in the study. We found a J-shaped exposure–response curve for all external causes of death, in which the risks increased for mild cold temperatures [20th percentile; relative risk $\left(\text{RR}\right)=1.09$ (95% confidence interval [CI]: 1.05,1.12)] and extreme heat [99th percentile; $\text{RR}=1.24$ (95% CI: 1.20, 1.29)] compared with those for minimum mortality temperature (MMT). However, the shapes of the exposure–response curves varied according to four subcategories. The risks of suicide and transport monotonically increased as temperature increased, with RRs of 1.35 (95% CI: 1.26, 1.45) and 1.60 (95% CI: 1.35, 1.90), respectively, for heat, whereas J- and U-shaped curves were observed for falls and drowning, with RRs of 1.14 (95% CI: 1.03, 1.26) and 1.95 (95% CI: 1.70, 2.23) for heat and 1.13 (95% CI: 1.02, 1.26) and 2.33 (95% CI: 1.89, 2.88) for cold, respectively, compared with those for cause-specific MMTs. The sex- and age-specific associations varied considerably depending on the specific causes.

Discussion:

Both low and high temperatures may be important drivers of increased risk of external causes of death. We suggest that preventive measures against external causes of death should be considered in adaptation policies. https://doi.org/10.1289/EHP9943

中文翻译：

---

1979 年至 2015 年日本的环境温度和外部死因：时间分层病例交叉分析

摘要

背景：

尽管大量证据表明高温和低温与非意外死亡率呈负相关，但很少有研究专注于探索温度对外部死亡原因的风险。

目标：

我们调查了 1979 年至 2015 年日本 47 个县的温度与外部死亡原因和四个特定类别（自杀、运输、跌倒和溺水）之间的短期关联。

方法：

我们进行了两阶段元回归分析。首先，我们使用分布式滞后非线性模型进行时间分层案例交叉分析，以检查每个县的温度与外部原因引起的死亡率之间的关联。然后，我们使用多元元回归模型来结合日本所有县的关联估计。此外，我们对性别和年龄的关联进行了分层分析。

结果：

共有 2,416,707 个外部死因被纳入研究。我们发现了所有外部死亡原因的 J 形暴露-反应曲线，其中轻度寒冷温度的风险增加 [第 20 个百分位；相对风险$\left(\text{RR}\right)=1.09$(95% 置信区间 [CI]: 1.05,1.12)] 和极端高温 [第 99 个百分位；$\text{RR}=1.24$(95% CI: 1.20, 1.29)] 与最低死亡率温度 (MMT) 相比。然而，暴露-反应曲线的形状根据四个子类别而变化。随着温度的升高，自杀和运输的风险单调增加，热的 RR 分别为 1.35（95% CI：1.26, 1.45）和 1.60（95% CI：1.35, 1.90），而 J 形和 U 形曲线观察到跌倒和溺水，热和 1.13（95% CI：1.02, 1.26）和 2.33（95% CI : 1.89, 2.88) 分别与针对特定原因的 MMT 相比。根据具体原因，性别和年龄特异性关联差异很大。

讨论：

低温和高温都可能是增加外部死因风险的重要驱动因素。我们建议在适应政策中考虑针对外部死因的预防措施。https://doi.org/10.1289/EHP9943