Heatwaves and Immigrant Mortality: An Assessment of Vulnerability and Temporal Variation

Immigrants are vulnerable to the adverse health impacts of climate change. However, little is known about the vulnerability and temporal patterns of heatwaves' effects on immigrants. Using daily mortality data from Hong Kong, this study compared the associations of mortality with heatwaves (two or more consecutive days with daily temperatures exceeding a certain threshold) between immigrants and nonimmigrants. We assessed immigrants' vulnerability by their age at immigration, origin, and residence duration and examined temporal trends in mortality risk. The heatwave-mortality association was significantly stronger among immigrants (relative risk: 1.088, 1.035-1.145) than nonimmigrants (0.975, 0.880-1.079). A higher heatwave-related mortality risk was observed in immigrants than their counterparts, particularly among those with a shorter length of residence (≤10 years), who immigrated to Hong Kong at a younger age (≤17 years) or older age (≥45 years), and who immigrated from mainland China. From 2000 to 2016, there was an upward trend in heatwave-related mortality risk among immigrants, while nonimmigrants had a downward trend. This study suggests that immigrants exhibit a higher heatwave-related mortality risk and a lower adaptive capacity. Protecting immigrants from hot weather is an urgent task, given that the scale of immigration is likely to increase as climate change continues.