Acute cardiac care & resuscitationMeta-analysis
Extreme temperatures and out-of-hospital cardiac arrest: a systematic review and narrative synthesis
- systematic review and narrative synthesis
- in accordance with PRISMA 2020 guidelines
- risk of bias assessed using the ROBINS-E tool
- registered prospectively with PROSPERO
Authors' conclusion
Extreme ambient temperatures represent significant, climate-sensitive and potentially modifiable determinants of OHCA incidence and outcomes. As climate change intensifies temperature variability and prolongs both heat and cold extremes, integrating environmental data into OHCA surveillance, risk forecasting, prevention strategies, and EMS planning becomes increasingly urgent.
Study context
- Population
- Observational studies examining the relationship between temperature extremes and OHCA incidence and outcomes, across Asia, Europe, North America, the Middle East, and Oceaniastudies included
- Participants
- Thirty-one studies
- Comparison
- the association between exposure to extreme ambient temperatures and the incidence and outcomes of out-of-hospital cardiac arrest (OHCA)
Pooled result
As reported in the abstract
OHCA incidence
- A U- or J-shaped exposure-response relationship was observed across most settings, with elevated OHCA incidence at both cold and hot temperature extremes
- effect magnitudes, thresholds, and lag structures varied substantially
Further pooled results
Temperature-attributable OHCAs
- Cold exposure accounted for a substantially greater proportion of temperature-attributable OHCAs compared with heat
Clinical outcomes (return of spontaneous circulation, survival to hospital discharge, neurological outcomes)
- Temperature extremes were also associated with poorer clinical outcomes, including lower rates of return of spontaneous circulation, reduced survival to hospital discharge, and worse neurological outcomes, particularly in periods of cold exposure
Study designs
- Most used time-series or case-crossover designs drawing on Emergency Medical Services (EMS) or cardiac arrest registry data
Original publication
Extreme temperatures and out-of-hospital cardiac arrest: a systematic review and narrative synthesis. Resuscitation. Published 22 July 2026. doi:10.1016/j.resuscitation.2026.111221
Summarised from the published abstract; every number is checked against it