The influence of extreme cold ambient temperature on out of hospital cardiac arrest: A systemic review and meta-analysis

Abstract

Abstract Objective Many researches have demonstrated the effects of the extreme cold ambient temperature on the risk of out-of-hospital cardiac arrest (OHCA); yet, the results have been inconsistent. We performed a meta-analysis to evaluate whether extreme cold ambient temperature is related to OHCA. Methods We searched for time-series studies reporting associations between extreme cold ambient temperature and OHCA in PubMed, web of science and Cochrane database. Results Six studies involving 2 337 403 cases of OHCA were qualified for our meta-analysis. The odds ratio (OR) of OHCA was significantly increased in extreme cold weather (defined as the 1st or 5th centile temperature year-round) compared to reference temperature (as the 25th centile temperatures or daily mean temperature with minimum risk of OHCA) (OR=1.49, 95% CI 1.18–1.88). The subgroup analysis for the elderly and the female failed to detect the influence of extreme cold weather on OHCA, the ORs are 1.25 (95% CI 0.89–1.75) and 1.19 (95% CI 0.87–1.64), respectively. Conclusion The risk of OHCA is significantly higher in extreme cold ambient temperatures than in reference temperature, according to a relative temperature scale with percentiles of the region-specific temperature distribution.