Differences in cardiovascular disease mortality between northern and southern China under exposure to different temperatures: a systematic review.

Background: Due to differences in climate and other environmental factors, exposure to different temperatures in China has different effects on the relative risk (RR) of cardiovascular disease (CVD) mortality. It is therefore important to compare the effects of exposure to different temperatures on CVD mortality in different regions of China.

Methods: To compare these effects, we performed a meta-analysis of 21 studies identified by a search of the Web of Science and China National Knowledge Infrastructure databases from January 1, 2014 to January 1, 2024. We performed the Cochran Q test and I ² statistics test to evaluate heterogeneity and Egger's test to evaluate publication bias.

Results: The pooled estimated size of the relationship between exposure to different temperatures and CVD mortality was 1.60 (95% confidence interval [CI]: [1.42-1.80]) for the extreme cold, 1.17 (95% CI [1.10-1.25]) for the extreme heat, and 1.16 (95% CI [1.10-1.24]) for extremely high diurnal temperature range (DTR). The Egger's test showed potential publication bias in studies analyzing both the extreme cold and the extreme heat.

Discussion: Extreme cold, extreme heat, and extremely high DTR are associated with an increase in CVD mortality in China, with extreme cold having the most significant effect. Residents of northern regions are more susceptible to high temperatures, while residents of southern regions are more sensitive to low temperatures.