Associations of long-term PM10 exposure with cardiovascular mortality and morbidity in South Korea: investigating the regional heterogeneity

Abstract

BACKGROUND AND AIM: Long-term exposure to ambient PM has long been linked to cardiovascular diseases. However, fewer studies have investigated non-fatal outcomes, especially in Asian regions, and little is known whether long-term health effects of PM are identical across the country. This study aimed to estimate the effects of long-term PM10 exposure on cardiovascular disease incidence and death in South Korea. We further examined effect modification by regional characteristics. METHODS: The study population comprised 317,204 subjects from the National Health Insurance Service-National Sample Cohort (2006-2015) residing in 120 districts where urban air monitoring stations are located. Incidence of cardiovascular disease was defined as the first occurrence of a hospital visit or admission among those with no previous history of cardiovascular disease. For each year of follow-up, we estimated a five-year moving window of past exposure to PM10 for each subject at the district-level. Time‐varying Cox proportional hazards models were used to assessing the relationship between PM10 and cardiovascular events. We conducted stratification analyses to explore effect modifications by metropolitan city indicator, district-level socioeconomic status indicators, and medical index. RESULTS:Each 10 μg/m³ increase in PM10 was associated with increased risk of both cardiovascular morbidity (hazard ratio, HR, 1.04; 95% CI, 1.02-1.07) and mortality (HR, 1.14; 95% CI, 1.03, 1.26). Subgroup analyses yielded competing results between cardiovascular mortality and morbidity. Effect estimate for cardiovascular morbidity was higher in the non-metropolitan area while the association with cardiovascular morbidity was higher in the metropolitan area. Districts with lower socioeconomic status had a larger increase in the risk of morbidity and had a lower increase in the risk of mortality CONCLUSIONS:This study supports the evidence that PM10 has long-term effects on cardiovascular health in South Korea. Regional vulnerability to PM10 might differ by the severity of the health outcome. KEYWORDS: Particulate matter, Long-term exposure, Cardiovascular diseases, Environmental justice, Environmental epidemiology