Influenza-like illness as a trigger for ischemic stroke

Area of Science:

• Neurology
• Infectious Diseases
• Epidemiology

Background:

• Influenza-like illness (ILI) is a common condition with potential systemic effects.
• The association between ILI and incident stroke risk requires further investigation.
• Understanding temporal relationships is crucial for identifying acute triggers of ischemic stroke.

Purpose of the Study:

• To investigate the association between influenza-like illness (ILI) and the risk of incident ischemic stroke.
• To determine if the risk of stroke is highest in the period immediately following an ILI episode.

Main Methods:

• A case-crossover analysis was conducted using the California State Inpatient Database.
• Exposure was defined as emergency department visits or hospitalizations for ILI within specific time windows prior to ischemic stroke.
• Conditional logistic regression was employed to calculate odds ratios (OR) and 95% confidence intervals (CI).

Main Results:

• A total of 36,975 ischemic strokes were analyzed, with 1.5% having a preceding ILI episode.
• The odds of ischemic stroke were highest within 15 days post-ILI (OR: 2.88, 95% CI: 1.86-4.47).
• The association between ILI and stroke risk diminished over time and was not significant after 60 days. A significant interaction with age was observed, with younger individuals (under 45) showing increased risk.

Conclusions:

• Influenza-like illness (ILI) is associated with a short-term increase in the risk of ischemic stroke.
• The risk appears to be highest in the immediate period following ILI, suggesting a triggering effect.
• Younger individuals (<45 years) experience a disproportionately higher stroke risk following ILI.