A recent study published in Neurology suggests that those who get a flu shot have a lower risk of stroke. An ischemic stroke is the most common form of stroke, and it happens when a blood clot restricts the flow of blood and oxygen to the brain.
Researchers used a nested case-control study and analyzed a Spanish healthcare database for individuals who were at least 40 years old and had their first stroke during the previous 14 years. The database included records from 2001-2015 and included 71,610 individuals who did not suffer a stroke and 14,322 people who did. Each stroke patient was compared to five other patients of the same age and gender. The researchers then looked at when patients had the influenza vaccination (at least 14 days prior to the stroke), or before that same date in the case of those who did not have a stroke. Adjusted odds ratios (AOR) and their respective 95% confidence intervals (CI) were calculated through a conditional logistic regression.
41.4% of patients who had a stroke had received the flu shot, compared to 40.5% of those who did not have a stroke. People who got the shot were more likely to be older and to have other health conditions such as high blood pressure that would increase susceptibility of having a stroke. After adjusting for those factors, researchers found that those who received a flu shot were 12% less likely to have a stroke than those who did not.
The researchers observed a reduced risk in pre-epidemic periods; this finding suggests that either the stroke protection is not totally linked to prevention of influenza infection, or unmeasured confounding factors may explain how the flu shot reduces stroke risk.
The study highlights the importance of receiving an annual flu shot. The Center for Disease Control recommends that anyone six months or older should get their flu vaccine annually.
Sources: Neurology, Science Tech Daily
