Joint Effects of Heat and Fine Particulate Matter on Out-of-Hospital Cardiac Arrest in Japan: A Nationwide Time-Stratified Case-Crossover Study.

Authors

Zhesi Yang, Chris Fook Sheng Ng, Kayo Ueda, Whanhee Lee, Massimo Stafoggia, Sunao Kojima, Takanori Ikeda, Yoshio Tahara, Naohiro Yonemoto, Masahiro Hashizume, Japanese Circulation Society with Resuscitation Science Study (JCS‐ReSS) Group

Published in

Journal of the American Heart Association. Pages e047917. Jul 17, 2026. Epub Jul 17, 2026.

Abstract

Out-of-hospital cardiac arrest (OHCA) is a leading cause of cardiovascular death. Although ambient temperature and particulate matter with an aerodynamic diameter ≤2.5 μm (PM_2.5) are established risk factors, evidence on their joint effects remains limited. We assessed the joint effects of heat and PM_2.5 on OHCA risk using nationwide data from Japan.
We collected daily data on cardiac-origin OHCAs from the All-Japan Utstein Registry and daily temperature and PM_2.5 from monitoring networks across 47 prefectures during 2012 through 2019. Using a 2-stage time-stratified case-crossover design, we estimated prefecture-specific associations with conditional quasi-Poisson models and pooled them using meta-regression. Interactions between temperature and PM_2.5 were assessed on multiplicative and additive scales using the relative excess risk due to interaction. Attributable cases were also estimated.
A total of 610 613 cardiac-origin OHCAs were included. Heat (relative risk, 1.04 [95% CI, 1.02-1.06]; 99th versus 80th percentile); and PM_2.5 (relative risk, 1.02 per 10 μg/m³ [95% CI, 1.01-1.03]) were independently associated with increased OHCA risk. Heat effects were amplified at higher PM_2.5 concentrations, with each 10 μg/m³ increase in PM_2.5 associated with an additional 1.8% increase in heat-related risk. Conversely, PM_2.5 effects increased by 1.2% (95% CI, 1.1%-1.2%) per 25th percentile increase in temperature. Interactions were observed on both scales (relative excess risk due to interaction, 0.01 [95% CI, 0.00-0.02]; P=0.003). Overall, 2638 OHCA cases were attributable to coexposure, exceeding the combined burden attributable to heat (1215) and PM_2.5 (1276) separately.
Heat and PM_2.5 acted synergistically to increase OHCA risk, highlighting the need for integrated public health strategies addressing both extreme heat and air pollution under climate change.

PMID:
42466507
Bibliographic data and abstract were imported from PubMed on 17 Jul 2026.

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