Abstract WP196: Seasonal Variation In Stroke Ischemic Hospitalization: Results From The A Large Health System In Six Western States Of The United States.

Abstract

Background: Evidence of seasonal variations in the incidence of stroke is inconsistent with some studies reporting no association and some a significant rise in different months of the year. In addition, less is known about how seasonality impacts the incidence of stroke subtype. Methods: This was a cross-sectional, observational study of data from a multi-state health system’s stroke registry (n=40 hospitals) in Alaska, California, Montana, Oregon, Texas, and Washington state. We included all cases with acute ischemic stroke admitted from September 29, 2016, to November 30, 2021. Admission data were categorized according to four meteorological seasons: winter, spring, summer, and fall. Acute ischemic stroke was categorized into two sub-types as large vessel occlusion (LVO) or non-LVO. We calculated the aggregate number of individuals admitted with stroke by season. Using, linear regression models with generalized estimating equations (GEE), we assessed the relationship between meteorological season and daily hospitalization rate. We used R version 4.0.4 (2021-02-15) for both the descriptive and inferential analyses and the R gee pack package (version 1.2-1) to perform GEEs. Results: During the study period, we identified 18,886 patients with acute ischemic stroke (median age: 73; 49.5% women). Acute ischemic stroke was more commonly observed during winter compared with other seasons with some variations between the selected regions. Based on a generalized estimating equations model, stroke hospitalization increased during winter, with an additional 3.3 cases per day (95%, CI [2.4, 4.1]). Winter is also associated with a higher incidence of large vessel occlusion. Conclusion: The incidence of ischemic stroke, including cases of large vessel occlusion, increased during the winter months. The results are important for human resource allocation for better management of cases with ischemic strokes.