Association of long–term exposure to PM2.5 with cause-specific mortality in elderly patients with the previous history of ischemic heart disease

Abstract

BACKGROUND AND AIM: Numerous studies have reported an association between fine particulate matter (PM2.5) and cardiovascular disease (CVD) morbidity and mortality. However, the association between PM2.5 and mortality among those with a previous history of ischemic heart disease (IHD) is less understood. We aimed to evaluate whether long-term exposure to PM2.5 is related to mortality after hospital discharge in elderly patients with IHD. METHODS: We followed-up 306,418 IHD elderly patients residing in seven major cities between 2008 and 2016 using the Korean National Health Insurance Database and identified cause-specific mortality after the hospital admission. We linked the modelled PM2.5 data corresponding to each patient’s administrative districts. We used time-varying Cox hazard models after adjusting for the individual- and area-level confounders. Subgroup analyses were conducted by age group (65–74 vs ≥ 75), sex, and income- and wealth-based insurance premiums. RESULTS:Of a total of 306,418 IHD elderly patients, 43.1 (%) were male, mean age was 76.8 years, and 105,913 died during a mean follow-up of 21.4 years. The adjusted hazard ratio (HR) of all-cause mortality was 1.10 [95% confidence intervals (CI): 1.07, 1.14] per 10 μg/m3 increase in a 12–month moving average PM2.5. The HRs were greater for cause-specific mortality: 1.17 (95% CI: 1.11, 1.24), 1.17 (95% CI: 1.06, 1.30), and 1.25 (95% CI: 1.15, 1.35) for CVD, stroke, and IHD, respectively. The subgroup analyses showed that for all–cause mortality, 65–74 age group, men, and low wealth-based insurance premiums were more susceptible to PM2.5 exposure. CONCLUSIONS:We found an association between long-term exposure to PM2.5 and mortality among elderly IHD patients, particularly for CVD-related mortality. Our results suggest that those with a previous history of IHD were more susceptible to PM2.5 exposure. KEYWORDS: Cohort Studies, Ischemic heart disease, Mortality,Particulate matter, Republic of Korea