The heart can cause death, but it can also cause a stroke or a break in the arteries of the neck, suggest two new studies.
The findinsg prompted an urgent reminder from researchers: First influenza shot not only will protect you from infection, but it can also reduce the risk of these serious complications.
The researchers in the first study showed that the flu could increase the chances of a stroke by almost 40 percent – and that the added risk remains for a whole year.
"The risk is highest in 15 days from the flu and it begins to decrease over time," says lead researcher Amelia Boehme. She is assistant professor of epidemiology at Vagelos College for doctors and surgeons at Columbia University in New York.
For the study, Boehme and her colleagues identified nearly 31,000 patients from a state-run New York State, an average age of 72 who had a stroke in 2014. As a group, they had a tendency to have severe cases of influenza because they were all seen in an emergency room or admitted to a hospital.
Boehme's team expects to find a difference in the risk of stroke between men and women, urban and rural residents and blacks and whites. Instead, the researchers found that the risk of a stroke is similar after the fight against the flu.
Other studies have shown that the risk of stroke increases after each major infection. It could be that in people who are already at risk of stroke, the flu causes one, said Boehme. But this study has not proven that the flu causes a risk of stroke to increase.
However, patients should be carefully observed after the flu, said Dr Salman Azhar, director of a stroke at the Lenox Hill Hospital in New York.
"What is interesting here is the flu not only increases the risk of stroke, but also that the risk is actually an extended risk, which lasts for several months," he said. "People need to be vaccinated."
Azhar doubts the inflammation that goes along with an infection, as the flu leaves the body vulnerable to strokes and heart attacks.
"Influenza puts your immune system in overdrive and you have a lot of inflammation, and it continues," he said. "It's not a one-and-done risk – the risk is there for several months."
In a second study, another group of Columbia University researchers found that in the month following an influenza epidemic, patients were more likely to break the arteries of the neck.
"Previous studies have shown that the non-traumatic Chinese artery kinesia is the leading cause of stroke in patients aged 15 to 45," said lead researcher Madeline Hunter, a medical student. "However, as dissections of the arteries of the neck without major trauma occur, it remains unclear."
Using the same data as in the first study, Hunter's team reviewed nearly 3,900 cases of cervical breakdown in men and women, an average age of 52 years.
They also identified more than 1,700 cases of influenza and found 113 cases where patients had a flu during the three years before they suffered a torn neck artery. The flu probably occurred 30 days before the tear.
"The fact that our study found a link between the flu and the cervical artery tear and that the association disappears over time suggests that the flu may be triggering," Hunter said.
Dr Mark Siegel, a professor of medicine at New York's Medical School in New York, reviewed the findings.
"Influenza causes a hyperimmune response and can increase clotting and arterial scarring," he said. But the problem with the flu is not just the flu, Siegel noted. On the contrary, it opens the door to other life-threatening diseases.
One of the insufficiently valued aspects of the flu is that if you get a flu, it will likely be a milder case, said Siegel. "I would expect complications like those that are extreme, to be less with fluid shots."
The findings should be presented on February 6-8 to the American Association for Stroke, an annual meeting in Honolulu. The studies presented at meetings are usually considered preliminary until they are published in a peer-reviewed journal.
To learn more about influenza and heart disease and stroke, visit the US Centers for Disease Control and Prevention.
SOURCES: Amelia Boime, MD, MSHP, Associate Professor, Epidemiology, College of Physicians and Surgeons of Vagelos, Columbia University, New York; Medlin Hunter, BA, medical student, Vagelos College for doctors and surgeons; Salman Azar, MD, director, stroke, Lennox Hill Hospital, New York; Mark Siegel, MD, clinical professor, medicine, Medical faculty in New York, New York; 6-8 February, 2019, presentations, Meeting of the Association for Stroke, Honolulu
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