Association between ambient temperature and out-of-hospital cardiac arrest: a systematic review and meta-analysis.

Out-of-hospital cardiac arrest (OHCA) is a leading cause of cardiovascular mortality worldwide. Although ambient temperature extremes have been linked to adverse cardiovascular outcomes, evidence regarding their association with OHCA remains inconsistent. We conducted a systematic review and meta-analysis to quantify the short-term effects of ambient temperature on OHCA risk. We systematically searched PubMed, Web of Science, and Embase from inception to September 30, 2025. for observational studies examining the association between ambient temperature and OHCA. Random- or fixed-effects meta-analyses were performed to pool relative risks (RRs) and 95% confidence intervals (CIs) for high- and low-temperature exposures. Subgroup analyses were conducted by temperature thresholds, sex, and age. Heterogeneity, publication bias, and sensitivity were assessed. A total of 23 studies conducted across Asia, North America, and Europe were included. High-temperature exposure was significantly associated with an increased risk of OHCA (RR = 1.067; 95% CI: 1.051-1.082), while low-temperature exposure showed a stronger association (RR = 1.192; 95% CI: 1.160-1.226). Substantial heterogeneity was observed for both high (I² = 91%) and low temperatures (I² = 96%), but sensitivity analyses confirmed the robustness of the pooled estimates. No statistically significant differences were identified across sex or age subgroups. Elevated risks were consistently observed across different percentile-based temperature thresholds, with the strongest associations noted at the 95th percentile for high temperature and across all examined low-temperature thresholds. Both extreme heat and cold are associated with an increased short-term risk of OHCA, with low temperature exerting a more pronounced effect. These findings highlight the importance of considering non-optimal ambient temperatures in OHCA prevention strategies and support the development of locally adaptive temperature-based early warning systems in the context of climate change.