Combined heat and air pollution exposure amplifies OHCA risk
13 hours ago
Heat and fine particulate matter appear to exert a joint effect on the risk of out-of-hospital cardiac arrest (OHCA), according to a study from Japan.
Researchers used cardiac‐origin OHCA data from the All‐Japan Utstein Registry and daily temperature and PM2.5 data from monitoring networks across 47 prefectures.
The analysis included a total of 610,613 OHCA of cardiac origin, with the daily mean number of cases being 209. Generally, PM2.5 levels in Japan during the 8-year study period were relatively low, within the environmental quality standards (daily average concentrations ≤35 μg/m3). However, air quality varied across prefectures. Daily mean temperatures fluctuated, owing to Japan’s geographic span and differences in altitude.
Heat showed a positive association with OHCA risk (99th vs 80th percentile: relative risk [RR], 1.04, 95 percent confidence interval [CI], 1.02–1.06), as did PM2.5 (per 10 μg/m3: RR, 1.02, 95 percent CI, 1.01–1.03).
The effect of heat on the risk of OHCA was amplified at higher PM2.5 concentrations, with each 10-μg/m3 increase in PM2.5 contributing to an additional 1.8-percent increase in heat‐related risk. Meanwhile, the effect of PM2.5 increased by 1.2 percent per 25th percentile increase in temperature. Interactions were observed on both scales (relative excess risk due to interaction, 0.01; p=0.003).
Overall, 2,638 OHCA cases were attributable to co-exposure to heat and PM2.5, exceeding the combined burden attributable to heat (n=1,215) and PM2.5 (n=1,276) separately.
The findings underscore the need for integrated public health strategies addressing both extreme heat and air pollution under climate change.