Roles of urban heat anomaly and land-use/land-cover on the heat-related mortality in the national capital region of South Korea: A multi-districts time-series study

The urban heat anomaly has been suggested as a representative risk factor for human health in metropolitan areas, but few studies have measured a quantitative increase in risk due to the urban heat anomaly on heat-related mortality in the summer season or assessed the role of various types of land-use/land-cover (LULC), which may contribute to the urban heat anomaly. In this study, we evaluated the association between the urban heat anomaly and heat-related mortality risk in the summer and the potential roles of multiple types of LULC indicators. We used district-level time-series and cadastral data from 51 urban districts in the national capital region of South Korea. We applied a two-stage analysis. In the first stage, we estimated the district-specific heat-related mortality risk by using a distributed lag non-linear model. In the second stage, we used a meta-analysis to pool the estimates across all districts and calculate the association between the urban heat anomaly/LULC indicators and heat-related mortality risk. We found that the higher urban heat anomaly was related to lower vegetation and higher urban surface indicators, and the urban heat anomaly was positively associated with the heat-related mortality risk. The association between the urban heat anomaly and the heat-related mortality risk was more pronounced in the elderly (age ≥ 65 years) and female population than in the non-elderly and male population. We also found that the LULC indicators affected the heat-related mortality only through the urban heat anomaly. Our findings indicate that urban areas may be more vulnerable to heat-related mortality risk as determined by the urban heat anomaly. These results suggest a need for urban heat mitigation strategies such as increased vegetation or surface albedo to help reduce heat-related mortality risk.