Temperature and Age-gender Effects on Out-of- hospital Cardiac Arrest Cases

Introduction: Temperature is a key factor influencing the occurrence of out-of-hospital cardiac arrest, yet there is no equivalent study in Hong Kong. This study reports results involving a large-scale territory-wide investigation on the impacts of ambient temperature and age–gender differences on out-of-hospital cardiac arrest outcome in Hong Kong. Methods: This study included 25,467 out-of-hospital cardiac arrest cases treated by the Hong Kong Fire Services Department between December 2011 and November 2016 inclusive. Simple correlation and regression analyses were used to examine the relationships between out-of-hospital cardiac arrest cases and temperature, age and gender. Calendar charts were used to visualise temporal patterns of pre-hospital emergency medical services related to out-of-hospital cardiac arrest cases. Results: A strong negative curvilinear relationship was found between out-of-hospital cardiac arrest and daily temperature (r ² > 0.9) with prominent effects on elderly people aged ≥85 years. For each unit decrease in mean temperature in °C, there was a maximum of 5.6% increase in out-of-hospital cardiac arrest cases among all age groups and 7.3% increase in the ≥85 years elderly age group. Men were slightly more at risk of out-of-hospital cardiac arrest compared with women. The demand for out-of-hospital cardiac arrest–related emergency medical services was highest between 06:00 and 11:00 in the wintertime. Conclusion: This study provides the first local evidence linking weather and demographic effects with out-of-hospital cardiac arrest in Hong Kong. It offers empirical evidence to policymakers in support of strengthening existing emergency medical services to deal with the expected increase in out-of-hospital cardiac arrest in the wintertime and in regions with a large number of elderly population.