Abstract T P163: Influenza-Like Illness is Associated With Risk of Ischemic Stroke: A Case-Crossover Analysis
Background: Acute triggers of ischemic stroke (IS) remain poorly characterized. Emerging evidence suggests infections may promote short-term pro-inflammatory, pro-coagulant states that precipitate stroke.
Objective: We hypothesized that exposure to influenza-like illness (ILI) is associated with increased risk of IS, as time intervals between events decrease.
Methods: HCUP/AHRQ administrative claims from all nonfederal hospitals in California (2009) were queried for IS, using a published ICD-9-CM surveillance algorithm, identifying 41,148 unique individuals. A patient identifier was used to link IS patients across hospitalizations with a validated algorithm for ILI using inpatient and emergency department records. For each IS case, ILI events within 15, 30, and 90-day risk periods preceding IS in 2009, were compared to the same time periods one and two calendar years prior (i.e., 2007 and 2008). A 4-day buffer period was used to ensure ILI preceded IS. Conditional logistic regression models, matched on individuals, were used to calculate odds ratios and 95% confidence intervals (OR, 95%CI) for given risk period, after adjusting for monthly prevalence and mean age of ILI hospitalizations. Effects stratified by age are also explored.
Results: Median (IQR) age of cases was 74 (62-83) years; 52.4% were female. There were more ILI during the 90-days preceding strokes in 2009 (n=439) than in the same stroke-free calendar period one year prior (n=303) and two years prior (n=81). ILI was associated with IS with decreasing magnitude of effect using windows of 15-days (adjusted OR 6.5, 95%CI, 2.2-19.7), 30-days (adjusted OR=3.7, 95%CI 1.7-8.3), and 90-days (adjusted OR=3.3, 95%CI, 1.9-5.8). The risk associated with ILI was higher among younger patients. Using the 30-day window, the association between ILI and IS was strongest among those 45-to-65-years (n=27,545, adjusted OR=2.53, 95%CI, 0.95-6.8).
Conclusion: Influenza-like illness may contribute to a heightened risk of ischemic stroke during short term periods post-infection, especially among younger patients. Presentation with influenza represents an opportunity for targeted prevention of stroke.
Author Disclosures: J.M. Luna: None. H. Kamel: None. J. Willey: None. K. Cheung: None. M.S.V. Elkind: None.
- © 2014 by American Heart Association, Inc.