Ambient Temperature and Mortality Due to External Causes: A Systematic Review

Background: External causes include accidents, injuries or health problems that arise immediately after accidents or other external factors. The purpose of this review was to collect information about the relation between temperature and mortality due to external causes. Methods: A systematic search of articles was conducted in PubMed, Scopus, Science Direct, Embase, and Web of Science until January 2017, with no restriction. Broad searches were conducted in all fields, using key words related to ambient temperature exposure and deaths due to external causes. Results: Nine articles were included in the study. Except two articles, one of which had been designed in a cross-sectional way and the other that was retrospective, the rest of the articles were ecological. The outcomes reported were heterogeneous and different metrics had been used in the results; therefore conducting of meta-analysis was not possible. Five articles had found direct and significant relations between high temperature and deaths due to external causes. Only one study found no relation. In the case of cold, one study showed that the proportion of death due to external causes was low during cold waves. Another study showed that there was no relation between cold waves and mortality due to external causes. But one article showed that death due to external causes increased on cold days, significantly. Conclusion: The results of this systematic review showed that high temperatures (heat) were more likely to cause mortality due to external causes than low temperatures (cold). Due to the small number of studies in this field, especially in the context of cold and death due to external causes, it is difficult to make robust conclusions.