Association between heat and hospital admissions in people with disabilities in South Korea: a nationwide, case-crossover study

Background: Despite extensive findings on the hazardous impacts of environmental heat exposure, little is known about the effect on people with disabilities. This study aimed to estimate the association between environmental heat exposure and emergency department admissions for people with disabilities compared with people without disabilities. Methods: In this nationwide, case-crossover study, we linked data on emergency department admissions (cases) for any cause in the warm season in South Korea from the Korean National Health Insurance Service (NHIS)–National Sample Cohort database (a nationally representative database of 1 million systematically sampled beneficiaries covering all ages) from Jan 1, 2002, to Dec 31, 2019, and short-term daily mean temperature exposure (measured via Google Earth Engine at a 9 km spatial grid, aggregated to district). We defined beneficiaries with disabilities as those who were registered as disabled in the NHIS; disabilities included in our study were physical disability, brain lesion disorders, blindness or vision loss, and deafness or hearing loss. Other types of disability were not included for confidentiality reasons. A time-stratified case-crossover design, in which participants served as their own control, was used with conditional logistic regression to estimate the association between heat and emergency department admissions in people with and without disabilities. Findings: 23 792 emergency department admissions were recorded for 59 527 people with disabilities. Of these 23 792 admissions, 10 234 (43·0%) individuals were female and 13 558 (57·0%) were male. The odds ratio (OR) of emergency department admissions associated with heat (99th temperature percentile vs 75th percentile) was 1·15 (95% CI 1·07–1·24) in people with disabilities and 1·06 (1·04–1·09) in people without disabilities. The annual excess number of emergency department admissions attributable to heat per 100 000 persons-years was 27·81 admissions (95% CI 9·20–45·69) and excess medical costs were US$638 739·47 (95% CI 201 900·12–1 059 641·87) in people with disabilities; these values were more than four times that of the non-disabled population. People with brain lesion disorders, people with severe physical disabilities, female individuals, and those aged 65 years or older showed higher heat risks. The risks of emergency department admissions due to mental disorder (1·89, 95% CI 1·18–3·00) and respiratory diseases (1·34, 1·06–1·70) also showed higher heat risks than for the other two analysed causes of admission (cardiovascular and genitourinary diseases). Interpretation: Heat was associated with increased risk of emergency department admissions for people with and without disabilities, but the risk appeared to be higher for those with disabilities. These results can inform policy makers when establishing action plans for people with disabilities. Funding: National Research Foundation of Korea, the South Korean Ministry of Environment, and the South Korean Ministry of Education.