Suffering a nasty bout of the flu or pneumonia is bad enough, but now research suggests it might also spell trouble for your heart.
In a study of nearly 2,000 people in Scotland, those who had battled the flu or pneumonia were six times more likely to suffer from a heart attack or stroke in the days after their sickness began.
But "for most young, healthy people, the risk of heart attacks and strokes occurring with a respiratory infection is [still] low," said lead researcher Charlotte Warren-Gash, an associate professor of epidemiology at the London School of Hygiene and Tropical Medicine.
However, the same doesn't hold true for people over 65 and those with heart disease, Warren-Gash noted.
"These folks should have vaccinations against influenza and pneumonia, the two bugs linked to highest heart attack and stroke risk," Warren-Gash said. "Understanding that there is a link between these bugs and heart attacks and strokes should be an added incentive to get vaccinated."
The findings are particularly noteworthy this flu season, since it has been such a severe one, said Dr. Marc Siegel, a professor of medicine at NYU Langone Medical Center in New York City.
He explained that flu and pneumonia rev up the immune system and stress the heart.
"Flu is the great enabler -- it enables other diseases," said Siegel, who wasn't involved with the study.
The flu puts such stress on the body that it invites pneumonia in, Siegel added. "Stress hormones are released, putting pressure on your body so you have a heart attack, and it also increases clotting that leads to heart attack," he said.
"If you have an underlying tendency toward heart disease, the inflammation that the flu unleashes will start a sequence that provokes heart disease," he said.
For the study, Warren-Gash and her colleagues used the Scottish Morbidity Record to collect data on 1,227 adults who suffered a first heart attack and 762 who had a first stroke and who also had a respiratory infection between 2004 and 2014.
The researchers investigated the rate of heart attacks and strokes in the times immediately after a respiratory infection and compared these rates with the rate of heart attacks or strokes in other periods of time in the same people.
Having a respiratory illness increased the risk of heart attack for up to a week after infection, and the risk of stroke for a month, the study showed.
Interestingly, the risk of having a first heart attack or stroke after getting the flu or pneumonia was greatest among those under 65, the researchers found.
Warren-Gash speculated that more people 65 and older get flu shots and the pneumonia vaccine, which may account for the greater risk seen among younger adults, who are less likely to get those shots.
Overall, the risk of heart attacks and strokes among those under 65 is still small, she added, but it's vital that people 65 and older get vaccinated.
These findings, published March 21 in the European Respiratory Journal , mirror those of a study published in the New England Journal of Medicine in January.
The findings in this latest study strengthen, but cannot prove, the theory that a flu infection can actually trigger a heart attack, the researchers noted.
For more on flu, visit the U.S. Centers for Disease Control and Prevention.
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