Association between long-term and short-term PM2.5 exposure and respiratory-related hospitalizations among a cohort of COPD patients, North Carolina, 2002-2015
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Approximately nine million adults in the United States are living with Chronic Obstructive Pulmonary Disorder (COPD). Previous research has found that short-term air pollution is associated with increased risk of hospitalization for COPD in older adults. The objectives of this study were to measure if there is an association between short-term ambient PM2.5 exposure and COPD hospitalizations, to measure if there is an association between long-term ambient PM2.5 exposure and COPD hospitalizations and to measure if the association between short-term exposure is modified by long-term exposure. The study population consists of a cohort of randomly selected individuals with electronic health records from the University of North Carolina Healthcare System, then restricted to patients with a COPD diagnosis from 2002-2015 (n=22,733). Estimated ambient PM2.5 concentrations are from a previously validated ensemble model. Binomial regression was used to estimate the Relative Risk (RR) (95%CI) of respiratory-related hospitalizations with 0 and 1-day lags of PM2.5, annual average of PM2.5, and their interactions; models were adjusted for individual race, and area level urbanicity, education, unemployment, and proportion on public assistance. We observed no evidence of an association with short-term exposures (RR for 1 µg/m3 increase in 1-day lag PM2.5: 0.99 (0.99, 1.00)), while the same increase in annual average PM2.5 was associated with increased risk of respiratory hospitalizations (1.06 (1.05, 1.08)). There was no evidence of interaction between long and short-term PM2.5 exposures. Long-term PM2.5 exposure, but not recent short-term exposure, was associated with respiratory related hospitalizations in COPD patients. Differences in associations may be related to behavioral differences in short-term periods (e.g., avoiding the outdoors on low air quality days) that are not possible for long-term exposures. This abstract does not reflect EPA policy.