The impact of non-optimum temperatures, heatwaves and cold spells on out-of-hospital cardiac arrest onset in a changing climate in China: a multi-center,time-stratified, case-crossover study

Background Out-of-hospital cardiac arrest (OHCA) is a time-critical and fatal medical emergency that has been linked to non-optimal temperatures. However, the future burden of OHCA due to non-optimal temperatures, heatwaves, and cold spells under climate change has not been well evaluated. Methods We conducted a time-stratified case-crossover study in 15 Northern Chinese cities throughout 2020 to estimate the exposure-response relationships of non-optimal temperatures, heatwaves, and cold spells with hourly OHCA onset in hot and cold seasons. We obtained future daily average temperatures by using 20 general circulation models under two greenhouse gas emission scenarios: one with certain emission control and the other with relaxed control. Lastly, we projected the change of OHCA burden under these two climate scenarios. Findings We analyzed a total of 29,671 OHCA patients and found that high temperatures and heatwaves as well as low temperatures and cold spells were all significantly associated with an increased risk of OHCA onset. Under the scenario of uncontrolled emissions, the attributable fraction (AF) of OHCA due to high temperatures and heatwaves would increase by 4.94% and 6.99% from the 2010s to 2090s, respectively. The AF due to low temperatures would decrease by 1.27% by the 2090s and the effects of cold spells were projected to be marginal after the 2050s. Under a medium emission control scenario, the upward trend of heat-related OHCA burden would become flat, and the decline in cold-related OHCA burden would also slow down. Interpretation Our study provides evidence of significant morbidity risk and burden of OHCA associated with global warming across Northern China. Our findings indicate that the increase in OHCA burden attributable to heat could not be offset by the decrements attributable to cold, emphasizing the importance of mitigation policies for limiting global warming and reducing the associated risks of OHCA onset. Copyright (c) 2023 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

This study evaluated the impact of future climate change on the burden of out-of-hospital cardiac arrest (OHCA) in Northern China due to non-optimal temperatures, heatwaves, and cold spells. The findings showed that high temperatures, heatwaves, low temperatures, and cold spells were all significantly associated with an increased risk of OHCA onset. Under global warming, the burden of OHCA attributable to heatwaves and high temperatures would increase, while the burden attributable to cold spells would decrease gradually.