Flu Can Raise Risk Of Heart Attack, Study Finds

The United States is in the grip of a severe flu season. So far, 37 children have died and nearly 12,000 patients are in hospitals nationwide. According to Centers for Disease Control and Prevention, the outbreak could surpass the figures from 2014-15, when 34 million people fell sick around the country.

Adding to the worry, a new study has linked influenza to higher rates of heart attack. The research found a six-fold increase in incidences of heart attacks in people within a week after a flu diagnosis had been confirmed.

“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. We were also surprised the risk dropped off to nothing by day 8 and beyond," Jeffrey Kwong, chief author of the study and a scientist at the Institute for Clinical Evaluative Sciences in Toronto, told Reuters.

Jeffrey and a team of Canadian researchers found that other respiratory diseases could also increase the risk of a heart attack, but not nearly as dramatically. The team, however, said it hadn’t examined whether the flu-related heart attacks were more fatal than other heart attacks.

Doctors have suspected a link between flu and heart attacks since the 1930s, but that connection has never been confirmed.

As part of the research, Kwong and his team studied 19,729 cases of lab-confirmed flu from mid-2008 through mid-2015 in Ontario. The researchers focused on 332 patients, aged 35 and above, who were admitted in hospital for a heart attack within a year before or after their flu diagnosis.

The study found there were 20 admissions per week in the seven days after diagnosis of the flu while there were only 3.3 admissions per week in the year before and after the flu diagnosis. 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 she was not surprised with the results.

“This time of year we frequently had people on the floor after the flu. It was often associated with pneumonia,” she said, adding, “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.”

Of the 332 people participated in the study who suffered at least one attack while recovering, 69 percent didn’t receive a flu vaccine shot. For 76 percent, it was their first heart attack, known as an acute myocardial infarction.

Influenza “is a stressor to the system. It can increase inflammation. When you get an infection your heart is beating faster. It can activate platelets, increasing the chance that blood clots will form in the arteries that serve the heart. All of these can increase the chance of having a heart attack,” Kwong said.

The study, titled “Acute Myocardial Infarction after Laboratory-Confirmed Influenza Infection,”was published in the New England Journal of Medicine on Thursday.