Impacts of precipitation during tropical cyclones and regional vulnerabilities on mortality in South Korea

Although tropical cyclones (TCs) bring not only strong winds but also heavy rainfall, the health impacts of precipitation during TCs remain unclear. We evaluated mortality risks associated with TC-accompanying precipitation and identified the regional characteristics contributing to vulnerability in South Korea. Daily TC-related maximum wind speeds were estimated using a wind field model and gauge-based precipitation was obtained from 2002 to 2019. Using nationwide time-series mortality data, we fitted quasi-Poisson regression models at each district with a distributed lag linear model to assess the association between the TC precipitation and mortality. A 10 mm/day increase in precipitation on TC days (defined by TC-related maximum wind speeds ≥17.5 m/s) was associated with an 11% (95% confidence interval [CI]: 8-14%) increased risk of all-cause mortality for three weeks following TC exposure. Through a meta-regression model, we found that an interquartile range increase in proportion of elderly and people with disabilities was associated with a 86.28% (95% CI: 9.34-217.37%) and 77.21% (0.72-194.44%) increase in relative risk (RR) of all-cause mortality due to TCs in low-rainfall regions, respectively, while the same increases were associated with a 38.12% (13.93-55.51%) and 42.31% (13.93-61.71%) decrease in RR in high-rainfall regions, respectively. Timely emergency room access was associated with a lowered TC risk in low-rainfall regions, and higher local tax per capita was associated with an increased TC risk in high-rainfall regions. Our findings suggest that integrating rainfall-driven risks and regional vulnerabilities into TC preparedness and disaster management strategies is essential.