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Equal heat, unequal harm: rural–urban disparity in heat-related illness and a burden-matched comparison of heat-alert design levers in Korea

Year: 2026
Type: preprint
Abstract: Heat warnings usually rest on a single temperature threshold, and the design debate has concentrated on two levers: the heat indicator, and localization. How often alerts are issued is rarely placed on the same scale. In a daily panel of 230 Korean municipalities, May–September 2019–2025 (244,430 area-days; 16,927 heat-illness emergency-department reports), standardized morbidity ratios (SMR) were estimated against a weather-only baseline and the three levers compared at a matched alert burden under four objective functions; rural municipalities were those below 500 persons/km². Exposure was near-identical and, if anything, marginally hotter in urban municipalities (mean daily maximum 27.83 vs 27.97°C), yet the rural SMR was 1.98 against 0.87, a ratio of 2.28 (95% CI 1.91–2.68); adding climate normals lowered it to 1.32, a lower bound given their collinearity with rurality. With the alert-day share fixed at 11.7%, percentile-matched thresholds captured 3.6 percentage points (pp) more cases than the single national rule and incidence-matched thresholds 1.2 pp more, though the latter captured 19.1 pp more rural cases. Switching the indicator yielded 0.8 pp, the two correlating at 0.95 daily. Raising the share to 28.7% increased case capture by 31.7 pp and Peirce skill by 17.2 pp, exceeding every lever on all four objectives — a gain in discrimination, not permissiveness. Half of all cases, about 1,160 a year, fall on non-alert days under the national 33°C rule. Alert frequency appears to dominate the debated levers; region-specific thresholds matter mainly on equity objectives, the indicator hardly at all.
DOI: 10.21203/rs.3.rs-10841434/v1
Author: Eunjung CHO
Language: English
Open Access status: green
OpenAlex ID: W7221763620
Cites: 31
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Related to: 10