Air pollutant exposure associated with increased readmissions after ischemic stroke
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Long-term exposure to air pollutants may be associated with increased readmissions after ischemic stroke, according to data published in Stroke.
“Long-term exposure to common air pollutants, even at levels below national limits, was associated with higher all-cause 30-day readmissions after ischemic stroke,” Phoebe M. Tran, PhD, MS, assistant professor in the department of public health at the University of Tennessee, and colleagues wrote. “These associations were present across hospital performance categories. Our findings are consistent with studies showing associations between long-term air pollutant exposure and increased readmissions among patients with myocardial infarction and heart failure.”
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The researchers gathered carbon monoxide (CO) and sulfur dioxide (SO2) data from the Environmental Protection Agency’s Air Quality System. Ozone (O3) and particulate matter 2.5 microns or less (PM2.5) data were collected from the EPA’s Fused Air Quality Surface Using Downscaling estimates. NASA’s total tropospheric column nitrogen dioxide (NO2) data were used as a proxy for surface NO2. Finally, environmental temperature data were retrieved from the Parameter-elevation Regressions on Independent Slopes Model Climate group.
Tran and colleagues also used publicly reported CMS performance data from 2012 to 2015 to categorize hospitals into three performance categories. Hospitals with a readmission rate less than 25th percentile of the national rate were deemed low. Those at more than the 75th percentile were designated high, and all others were intermediate.
The researchers found that 12.5% of the 448,148 patients discharged with ischemic stroke were readmitted within 30 days.
For each 1 standard deviation (SD) increase in average annual CO exposure, there was a 1.5% (95% CI, 0.7-2.2) increased risk for 30-day readmission. For NO2, the increased risk was 5.2% per 1 SD (95% CI, 4.5-5.9). A 1 SD increase in PM2.5 was associated with an increased readmission risk of 2.4% (95% CI, 1.4-3.5), and a 1 SD increase in SO2 was associated with a 1.4% (95% CI, 0.5-2.4) increased risk for readmission.
The researchers found a slight inverse association between O3 and readmission of 0.7% (95% CI, 0-1.5), but this became insignificant after covariate adjustment.
When the researchers conducted analyses by hospital performance categories, they found the relationship between increase in pollution exposure and readmission after ischemic stroke remained.
“An American Heart Association statement emphasized the importance of policy interventions to reduce air pollution-associated CVD burden, and our findings, along with studies of other CVD conditions, suggest that a reevaluation of air pollution regulations may be warranted,” Tran and colleagues wrote.
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