Spatial and temporal characteristics of temperature effects on cardiovascular disease in Southern China using the Empirical Mode Decomposition method.

Until now, few studies have analyzed the effects of temperature on cardiovascular disease (CVD) death at different time points. In this study, we chose 9 different cities in the subtropical and tropical areas of China and analyzed the correlation between temperature at different time points and CVD mortality. We completed this study in two steps. First, we analyzed different time trend decomposition data related to CVD mortality in different populations within the 9 selected cities using empirical mode decomposition (EMD). Second, we created a regression fitting analysis of CVD mortality and temperatures at different time periods. The results showed that the CVD mortality of subtropical and tropical areas in southern Chinese cities represented spatial heterogeneity. The CVD mortality rates in Beihai, Hefei and Nanning showed rising trends, whereas the CVD mortality rates in Haikou, Guilin and Changde appeared to be decreasing. At the daily, seasonal and year time scales, low temperatures were negatively correlated with CVD mortality. Other than at the daily time scale, high temperatures did not significantly influence CVD mortality. This article will help to develop appropriate measures to reduce temperature-related mortality risk in different populations within the subtropical and tropical regions of China.