Association between long-term and short-term PM2.5 exposure and hospitalizations among a cohort of COPD patients, North Carolina, 2002-2015
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BACKGROUND:
Approximately nine million adults in the United States are living with Chronic Obstructive Pulmonary Disease (COPD). Previous research has reported associations between short-term air pollution exposures and increased risk of hospitalization for COPD in older adults. This study examined associations individually between short-term and long-term PM2.5 exposure and hospitalizations, and whether the association between short-term PM2.5 exposure is modified by long-term PM2.5 exposure in a cohort of individuals with COPD.
METHODS:
The study population consists of a cohort of randomly selected individuals with electronic health records from the University of North Carolina Healthcare System that had a COPD diagnosis from 2002-2015 (n=1,429). Estimated ambient PM2.5 concentrations are from a previously validated ensemble model. Poisson regression was used to estimate the Risk Ratios (RR (95%CI)) of cardiovascular disease (CVD) and all-cause hospitalizations with 0-2 day lags of PM2.5, annual average PM2.5 concentrations, and their interactions. Models were adjusted for individual race, and area-level urbanicity, education, unemployment, and proportion on public assistance.
RESULTS:
Among the 1,429 COPD patients in our cohort there were 4,302 inpatient hospital visits recorded, including 3,559 CVD-related visits. The mean short-term PM2.5 concentration was 9.62 µg/m3 (IQR 6.77-11.45); the mean long-term PM2.5 concentration was 9.83 µg/m3 (IQR 8.73-10.34). We observed a null association with CVD (RR=1.01 (1.00, 1.02) and a small association with all-cause (RR=1.03 (1.02, 1.04)) hospitalizations per unit increase of short-term PM2.5. There were positive associations between long-term exposure and CVD hospitalizations (RR=1.12 (1.09, 1.16) and all-cause hospitalizations (RR=1.20 (1.17, 1.23)). There was no evidence of interaction between long- and short-term PM2.5 exposures with CVD hospitalizations (RR=1.19 (1.07, 1.32), ICR 0.06) and all-cause hospitalizations (RR=1.21 (1.14, 1.29), ICR -0.02)
CONCLUSIONS:
Our preliminary results show associations between short- and long-term PM2.5 and CVD and all-cause hospitalizations among COPD patients, but no evidence of interaction between exposure periods.