Short-Term Ambient Air Pollution and Acute Osteoarthritis Morbidity Across Population Subgroups: A Nationwide Case-Crossover Study of Hospital Visits in South Korea.

Abstract

Osteoarthritis (OA) is a leading cause of disability, yet its acute environmental triggers remain poorly understood despite rising healthcare demand in aging societies. Short-term exposure may aggravate established OA, but claims-based visit dates reflect healthcare utilization rather than confirmed symptom onset. We linked the Korean National Health Insurance Service-National Sample Cohort (2002-2019) with nationwide air pollution data to examine short-term associations between six ambient pollutants (PM10, PM2.5, NO2, SO2, O3, and CO) and OA-related hospital visits (ICD-10 M15-M19). Using a time-stratified case-crossover design, we assessed subgroup-specific susceptibility across demographic, socioeconomic, lifestyle, and clinical characteristics using linked health-screening data. Among 3,697,314 OA-related visits, all six pollutants were positively associated with visits per interquartile range (IQR) increment: 5.28% (95% CI, 5.02-5.54) for NO2, 2.88% (2.59-3.16) for CO, 1.36% (1.10-1.63) for SO2, 0.90% (0.73-1.07) for PM10, 0.76% (0.44-1.08) for O3, and 0.73% (0.47-1.00) for PM2.5. After correction for multiple comparisons, pollutant-specific effect modification was observed for sex, age, residential area, insurance type, smoking, alcohol use, physical activity, body mass index, and comorbidity burden. In two-pollutant and principal-component analyses, the NO2 association remained robust and the mixture components were positively associated with visits. These findings extend the health burden of air pollution to acute musculoskeletal morbidity in a lower-exposure East Asian setting where these effects remain policy-relevant. By resolving susceptibility across multiple individual-level domains rarely available in prior studies, our study provides evidence to inform targeted environmental health protection in aging populations.