Abstract WMP49: Influenza-Like Illness May Trigger Cervical Artery Dissection

Abstract

Background and Purpose: Non-traumatic Cervical Artery Dissection (CeAD) is a leading cause of ischemic stroke in patients 15 to 45 years old. Influenza-like illnesses (ILI) have been found to trigger ischemic stroke, but ILI has not been investigated in relation to CeAD. We hypothesized that ILI and influenza would be associated with CeAD. Methods: We used a case-crossover design among patients > 18 years old at time of first non-traumatic CeAD within the New York State (NYS) Department of Health Statewide Planning and Research Cooperative System (2006-2014). We used ICD-9 codes to define CeAD (443.21, 443.24) excluding individuals with major trauma (integer values 800-804 and 850-854), confirmed influenza (480, 487.0, 487.1, 487.8), and a broader influenza definition endorsed by the CDC for ILI surveillance. We compared ILI and influenza in sequential, mutually exclusive intervals preceding CeAD (0-15, 16-30, 31-90, 91-180, and 181-365 days prior to CeAD: case period) and overlapping intervals (0-30, 0-90, 0-180, and 0-365 days prior to CeAD: alternate case period) to ILI and influenza exactly one and two years earlier (control periods). Conditional logistic regression models were used to calculate odds ratios and 95% confidence intervals (OR, 95% CI) before and after adjusting for annual NYS population estimates of influenza prevalence rate. Results: Our final sample included 3,861 cases of CeAD (mean age 52±16 and 55.5% of male). We found 1,736 instances of ILI and 113 of influenza during the 3 years preceding CeAD. Patients were more likely to have ILI within 30 days of CeAD compared to the same time one and two years before (0-15 days: adjusted OR 1.53, 95% CI 1.02 - 2.30; 0-30 days: adjusted OR 1.60, 95% CI 1.14 - 2.23). ILI during later overlapping or sequential intervals was not associated with CeAD in adjusted models. Influenza was associated with CeAD between 31 and 90 days after CeAD, but this effect was no longer significant after adjusting for prevalence rate of influenza, perhaps due the small number of patients with confirmed influenza. Conclusions: ILI may increase risk of CeAD for up to one month. Further research on mechanisms by which ILI and influenza may trigger dissection are warranted.