Abstract 61: Seasonal Variation of In-Hospital Mortality in Patients with Acute Ischemic Stroke
Background and objectives: Seasonal patterns in incidence and mortality are well known for cardiovascular diseases (CVD) including acute myocardial infarction and arrhythmias. It is unclear whether in-hospital mortality in patients with acute ischemic stroke (AIS) exhibits seasonal variation.
Methods: We searched the 2011 Nationwide Inpatient Sample for discharges with a principal diagnosis of AIS using the ICD-9 codes 433.01, 433.11, 433.21, 433.31, 433.81, 433.91, 434.01, 434.11, 434.91 and 437.1. Seasonal variation in in-hospital mortality was tested using logistic regression with admission season and month as categorical predictors in separate models. In addition to annual variation, we tested for the “July effect” of increase in mortality in teaching hospitals.
Results: There was an estimated 467, 849 discharges for AIS of which 21,149 (4.53%) died in the hospital. Compared to summer months, the risk of in-hospital mortality was 12.6% higher in winter and 10.2% higher in the fall (p=0.004 for winter vs. summer, p=0.024 for fall vs. summer). Compared to August, mortality was 18.20% higher in January (p=0.026 for comparison) and 24.3% higher in December (p=0.003 for comparison) (Table shows odds ratio of death compared to reference season/month). We did not find any evidence of a “July effect” of increased mortality, often attributed to new trainees, in teaching hospitals (p=0.830 for June vs. July)
Conclusions: In a large national database of hospital discharges related to AIS, mortality was significantly higher in colder months compared to warmer months. Our study adds to the growing body of evidence that links winter season to worse outcomes in CVD.
Author Disclosures: N. Kumar: None. N. Garg: None. M. Khunger: None. A. Venkatraman: None.
- © 2015 by American Heart Association, Inc.