Abstract 165: Nationwide Seasonal Variations And Increases In Incidence Of Intracerebral Hemorrhage And Acute Ischemic Stroke: An Analysis Of Pre-pandemic 16-year National Data

Introduction:There is paucity of evidence on long-term nationwide trends and seasonal variation in incidence of Intracerebral Hemorrhage (ICH) and Acute Ischemic Stroke (AIS).Methods:Using the Nationwide Inpatient Sample (2004 - 2019), we identified adults (≥ 18 years) discharged with primary diagnosis of ICH and AIS. We aggregated hospitalizations across quarters: Jan - Mar (Q1); Apr - Jun (Q2); Jul - Sep (Q3) and Oct - Dec (Q4). We used survey weights to calculate nationally representative estimates of quarter-specific incidence across age, sex, and race/ethnicity sub-cohorts and obtained time-specific denominators from the US Census Bureau. We calculated per quarter incidence rate (IR) across Q1-Q4 and Q2-Q3. We used multivariable Poisson regression model to report the adjusted incidence rate ratio (aIRR) and 95% confidence interval (CI) for the differences in quarterly incidence between Q1Q4 and Q2Q3.Results:Across 16 years, 985 959 ICH and 7 067 178 AIS hospitalizations were evaluated. The average quarterly crude IR of ICH in Q1Q4 of 6 per 100 000 was higher than the average rate of 5.4 per 100 000 observed in Q2Q3 (aIRR, CI: 1.10, 1.09 - 1.10). However, for AIS the average quarterly IR of ICH in Q1Q4 (41.2 per 100 000) was similar to the incidence rate in Q2Q3 (41.2 per 100 000) (aIRR, CI: 1.00, 1.00 - 1.00). Furthermore, we observed that average quarterly incidence is increasing overtime (aIRR, CI) for both ICH (1.01, 1.01 - 1.01) and AIS (1.03, 1.03 -1.03). The aIRR and CI for age, race, and sex are provided in the figure.Conclusion:Both stroke phenotypes demonstrate an increasing nationwide incidence. However, unlike AIS, ICH incidence is consistently and significantly higher in the months of October to March. Additional evaluation of factors such as holiday stress, seasonal variations in health behaviors (diet, physical activity, medication adherence) and physiological parameters (blood pressure, blood viscosity, fibrinogen, and cholesterol levels) is warranted.