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In adults with chronic obstructive pulmonary disease (COPD), long-term exposure to fine particulate matter of less than 2.5 µm in diameter (PM2.5) was associated with an increased risk for cardiovascular (CV) mortality, according to the results of a retrospective cohort study. Results of the analysis were published in the American Journal of Respiratory and Critical Care Medicine.
Recognizing that air pollution, especially PM2.5, is a modifiable risk factor for both COPD and cardiovascular disease, researchers sought to assess the link between long-term particulate matter and risk for CV events among adults with COPD from the Kaiser Permanente Northern California (KPNC) health plan between 2007 and 2016. Eligibility requirements for the study included the following: having a clinical diagnosis of COPD, being at least 18 years of age, having a KPNC health plan membership for at least 1 year and 1 outpatient utilization, resident in the 35-county Northern California region for at least year, and a home address that was geocoded successfully and was linked to air pollution exposure data. A total of 3 CV endpoints were evaluated: (1) acute myocardial infarction (AMI), (2) stroke, and (3) CV mortality. A combined endpoint was defined as satisfying any of these CV events.
A total of 169,714 adult patients with COPD who were members of the KPNC health plan were included in the study. The mean participant age was 60.8 years; 56.2% of the patients were women. Many of the participants were overweight (32.9%) or obese (38.1%). Hypertension and hyperlipidemia were common comorbidities, reported in 53.1% and 47.4% of the participants, respectively.
Daily PM2.5 exposures were obtained from a validated state-of-the-art ensemble model. Individual-level, time-varying 1-year PM2.5 exposures were constructed for all study participants. All of the exposures were updated each month, from baseline to the end of follow-up, and accounted for moving.
Results of the study showed that in adults with COPD, a 10-µg/m3 increase in exposure to 1-year mean PM2.5 was associated with an increased risk of CV mortality in the minimally adjusted model (hazard ratio [HR], 1.27; 95% CI, 1.17-1.38) and an HR of 1.10 (95% CI, 1.01-1.20) in the fully adjusted model. The outcomes for AMI, ischemic heart disease mortality, and the combined endpoint of any CV event were associated with 1-year average PM2.5 exposure in the minimally adjusted models but not in the fully adjusted models.
Statistically significant differences were observed between men and women (P =.007), with risks shown to increase among men but not among women (HR, 1.21; 95% CI, 1.08-1.36 and HR, 0.98; 95% CI, 0.87-1.11, respectively). Stronger effects were also reported in low socioeconomic status neighborhoods compared with high socioeconomic status neighborhoods (P =.034).
According to fully adjusted models, 1-year average PM2.5 exposure was associated with increased risk for CV mortality (HR, 1.88; 95% CI, 1.56-2.27), AMI (HR, 1.52; 95% CI, 1.17-1.96), ischemic heart disease mortality (HR, 1,84; 95% CI, 1.42-2.39), and the combined endpoint of any CV event (HR, 1.62; 95% CI, 1.40-1.88). Both stroke and cerebrovascular mortality associations were indicative of higher risk.
A limitation of the current study is the fact that it did not explore time windows of more than 1 year, which might prove to be valuable in future work. The present analysis concentrated on 1-year mean exposures, because that is the time window regulated in California and in the United States. The investigators concluded that the findings from this study suggest that current regulations are not sufficiently protective of adults with COPD, based on the fact that an elevated risk for CV events was reported at PM2.5 exposure levels lower than the current regulation level of 12 µg/m3 for 1-year mean exposure.
Reference
Alexeeff SE, Deosaransingh K, Liao NS, Van Den Eeden SK, Schwartz J, Sidney S. Particulate matter and cardiovascular risk in adults with chronic obstructive pulmonary disease. Am J Respir Crit Care Med. Published online March 4, 2021. doi:10.1164/rccm.202007-2901OC
