The effect of heat waves on mortality and effect modifiers in four communities of Guangdong Province, China

Heat waves have been reported to be associated with increased mortality; however, fewer studies have examined the effect modification by heat wave characteristics, individual characteristics and community characteristics. This study investigated the effect of extreme heat on mortality in 2 urban and 2 rural communities in Guangdong Province, China during 2006–2010. The effect of extreme heat was divided into two parts: main effect due to high temperature and added effect due to prolonged heat for several consecutive days. A distributed lag non-linear model was used to calculate the relative risk with consideration of lag days and potential confounding factors. Separate models were further fit by individual characteristics (cause of death, age and gender) and heat wave characteristics (intensity, duration and timing), and potential effect modification of community characteristics was examined using a meta-regression, such as educational levels, percentage of the elderly, Gross Regional Domestic Product (GDP). The overall main effects (ER = 8.2%, 95% CI: 3.4%, 13.2%) were greater than the added effects (ER = 0.0%, 95% CI: − 3.8%, 4.0%) on the current day. The main effect peaked at lag0–2, and was higher for the two rural areas compared to the two cities, for respiratory compared to cardiovascular mortality, for those ≥ 75 years old and for females. The modifying effects of heat wave characteristics and community characteristics on mortality were not statistically significant. This study suggests the effects of extreme heat were mainly driven by high temperature, which can be modified by some individual characteristics. • Mortality effects of extreme heat were mainly explained by high temperature. • Extreme heat effects were higher for the rural areas than urban areas. • Extreme heat effects were higher for respiratory mortality, for the elderly and for females.