Background: Of the many complications associated with COVID-19 infection, hypercoagulable states with subsequent thrombosis are some of the most feared implications. When trying to uncover a potential relationship between COVID-19 infection and risk for cerebrovascular ischemic events, knowing whether there is an increased risk for these events in those with other respiratory viral pathogens at baseline becomes essential. The one viral respiratory pathogen with more robust data regarding elevated risk of acute ischemic stroke is Influenza. In one large cohort study, 554 out of 36,975 patients with ischemic strokes had at least one episode of influenza-like illness (ILI) in the 365 day risk period prior to their stroke and the odds of ischemic stroke were greatest in those who were 15 days out from influenza-like illness onset (OR: 2.88, 95% CI: 1.86-4.47), with the relationship between the two variables decreasing as time from ILI increased. Thus, in order to gauge the true propensity for those with COVID-19 infection to develop a hypercoagulable state that predisposes to cerebrovascular ischemia, rather than comparing to the general population’s risk, a fairer control can be found in Influenza virus infected patients. At this time, there are few studies that have been conducted comparing the relative risk of TIA/Stroke in those infected with COVID-19 versus Influenza, with the most notable study suffering from methodologic issues that limit generalization to a broader population and lower power.
Methods: We conducted a retrospective analysis of hospitalized COVID-19 and Influenza patients diagnosed with TIA/Stroke in the HCA hospital network between Jan 2020 and June 2020. Chi Square test was used to examine the association between COVID-19/Influenza diagnosis and TIA/Stroke diagnosis. Odds ratio was used to examine the likelihood of TIA/Stroke incidence in COVID-19 patients when compared to Influenza patients.
Results: The study included 89,469 patients. There was an association between TIA/Stroke and COVID-19/Influenza diagnosis at the 95% (α=.05) confidence limit (P=<.0001). Of Patients with COVID-19 [25,156 (28.06%)], 139 (0.55%) had a stroke. Of Patients with Influenza [64,313 (71.75%)] , 129 (0.20%) had a stroke. Looking at the odds ratio, patients that have COVID-19 are 2.273 times as likely to have a TIA/Stroke as opposed to those that have influenza at a 95% Wald confidence limit of 1.541 and 3.352. The average age in patients with COVID-19 and stroke was 68.46 years and the average age in patients with Influenza and stroke in 2020 was 65.39 years. Logistic regression was used to correct for age, sex, and race. Patients with COVID-19 are 2.273 times more likely to have a TIA/Stroke compared to patients with influenza, correcting for age, sex, race differences between the two cohorts.
Conclusions: TIA/Stroke are serious complications of COVID-19 infection. Our study suggests that there is an association between COVID-19 infection and the incidence of TIA/Stroke. The study also finds that COVID-19 patients can be more than twice as likely to suffer from a TIA/Stroke. There was no statistically significant age difference between the COVID-19 group and Influenza group.