Flu increases risk of heart attack

Influenza is already known to be deadly, but a new study suggests that the risk of heart attack is six times greater than normal while people are ill with the flu. "I was a little bit surprised by the strength of the association. It's not every day you see a six-fold increase in the risk during the first seven days of lab-confirmed influenza," chief author Dr Jeffrey Kwong told Reuters Health in a telephone interview. "We were also surprised the risk dropped off to nothing by day 8 and beyond."
He and his Canadian team also found that other respiratory diseases can also increase the chance of a heart attack, but not as nearly as dramatically. The group, reporting in The New England Journal of Medicine, did not examine whether flu-associated heart attacks are deadlier.
The new study reinforces the importance of the flu vaccine and protective measures such as regular hand washing to guard against influenza and other infections, said Dr Kwong, a scientist at the Institute for Clinical Evaluative Sciences in Toronto. Doctors have suspected a link between flu and heart attacks since the 1930s, but in that era it was hard to know if the influenza virus or a flu-like illness had made a patient sick prior to the heart attack. Kwong and his colleagues used confirmed cases of flu, analyzing 364 heart attacks from mid-2008 through mid-2015 among Ontario residents age 35 or older who were registered with the province's publicly funded health insurance program.
The heart attack rate was 20.0 admissions per week during the seven days after diagnosis of the flu, versus 3.3 per week during the 52 weeks before and 51 weeks after that seven-day window.
The risk dropped off dramatically by the eighth day after diagnosis. Dr Erica Jones, director of the HeartHealth Program at Weill Cornell Medicine and New York-Presbyterian Hospital, who was not connected with the study, said the results aren't surprising based on her experience with hospitalized heart attack patients. "This time of year we frequently had people on the floor after the flu," she told Reuters Health by phone. "It was often associated with pneumonia."