Abstract WMP98: Associations Between Long-term Co, No ₂ , O ₃ , Pm _2.5 , And So ₂ Exposure And 30-day All-cause Hospital Readmission Among Stroke Patients In The Us: 2014-2015

Objective: There are known associations between long-term air pollution exposure and greater stroke incidence, morbidity, and mortality; however, there is little research on the association of pollutant exposure with poststroke hospital readmission. Methods: We assessed associations of average annual CO, NO 2 , O 3 , PM 2.5 , and SO 2 exposure with 30-day all-cause hospital readmission in US fee-for-service Medicare beneficiaries age ≥65 years hospitalized for ischemic stroke in 2014-2015. We fit Cox models to assess 30-day readmission as a function of these pollutants, adjusted for patient and hospital factors and temperature. We repeated the models stratified by performance of the treating hospital on the Centers for Medicare & Medicaid Services (CMS) risk-standardized 30-day all-cause readmission for stroke measure to determine if the results were independent of performance: Low (CMS rate for hospital <25th percentile of national rate), High (>75 th percentile), and Middle (all others). Results: There were 448148 patients discharged with stroke in 2014-2015 of whom 12.5% were readmitted. Average 2-year CO, O 3 , PM 2.5 , and SO 2 values during the study were below national standards. In adjusted analyses, each 1 standard deviation increase in average annual NO 2 and SO 2 exposure was associated with a 3.6% (95% CI 2.9%-4.4%) and a 2.0% (95% CI 1.1%-3.0%) increased readmission risk within 30-days, respectively ( Table ). Associations between long-term air pollution exposure and increased readmissions persisted across performance categories. Conclusion: Long-term air pollution exposure was associated with increased 30-day readmissions after stroke at pollutant levels below national standards across hospital performance categories. Additional research is needed to determine whether improvements in air quality lead to reductions in poststroke hospital readmissions.