A case-crossover study on impacts of heat wave on daily mortality and disease burden among residents in Pudong New Area, Shanghai

Background With the continuous warming process of global climate, the frequency and the intensity of heat wave are increasing, and the health impact of heat wave has caused widespread concern around the world.

Objective This study aims to explore the effects of heat wave on daily death count and disease burden among residents in Pudong New Area, Shanghai.

Methods Data of daily non-accidental, cardiovascular disease, and respiratory disease mortalities from May to September during 2005-2017 were collected, and the contemporaneous meteorological factors and air pollution (PM₁₀, SO₂, and NO₂) were also retrieved. A time stratified case-crossover design with a distributed lag nonlinear model (DLNM) to control the secular trend of time was performed to quantitatively evaluate the impacts of heat wave on daily death count and years of life lost due to non-accidental, cardiovascular disease, and respiratory disease mortalities among residents in Pudong New Area. A stratified analysis was performed to examine the effects of gender, age, and educational attainment.

Results During the study period, a total of 25 heat wave events were registered, and cumulatively lasted for 148 days. There reported 93 040 non-accidental deaths, including 33 402 residents died of cardiovascular disease and 8 842 of respiratory disease. Heat wave was associated with the increased risk of non-accidental mortalitiesRR=1.13, 95% CI:1.06-1.19 and years of life lost58.68 (95% CI: 6.70-110.67) person years at lag 0-5 days versus non-heat wave. The RRs were 1.23 (95% CI:1.12-1.35) and 1.23 (95% CI:1.03-1.48) for cardiovascular and respiratory mortalities, and the YLLs increased 42.40 (95% CI:18.10^-66.71) person years and 12.09 (95%CI:1.45-22.73) person years, respectively. The RRs and increased years of life lost for the group with primary school and below educational attainment were 1.19 (95%CI:1.11-1.27) and 58.22 (95%CI:23.01-93.44) person years at lag 0-5 days, which were higher than 1.05 (95%CI:0.96-1.16) and 0.46 (95% CI:-36.72-37.63) person years for the group with middle school and above education.

Conclusion Heat wave events can elevate non-accidental, cardiovascular, and respiratory mortalities and years of life lost among residents in Pudong New Area of Shanghai, with obvious cumulative and lag effects. The group with primary school and below education is more susceptible to the impacts of heat wave.