Staving off flu lowers heart attack risk: study

Preventing the flu can lower the chances of a first heart attack in some people, according to a new study.

Since heart attacks increase significantly in the winter when pneumonia and flu are common, researchers have suggested there may be a link between respiratory infections and heart attacks.

The link was tested in Monday's online issue of the Canadian Medical Association Journal, where it was revealed that researchers from the United Kingdom looked at 78,706 patients aged 40 years or older from 379 family practices in England and Wales.

Of the total, 16,012 had had a heart attack and 8,472 of the patients had been vaccinated.

Early vaccination for flu between September and mid-November was associated with a 21 per cent reduction in the rate of heart attacks compared with late vaccination after mid-November, which was associated with a 12 per cent reduction.

"Our findings reinforce current recommendations for annual influenza vaccination of target groups, with a potential added benefit for prevention of acute myocardial infarction in those without established cardiovascular disease," wrote Dr. Niroshan Siriwardena of the University of Lincoln, with co-authors Stella Gwini and Carol Coupland.

Pneumococcal vaccination was not linked to a reduction in the rate of heart attacks, the researchers found.

Plaque rupture

The study's authors took into consideration that people with risk factors for heart attacks were more likely to be vaccinated thanthose with no risk factors.

"Flu vaccination may be linked to a reduction in risk of heart attack," Siriwardena said.

"As well as preventing flu and respiratory problems linked to flu, that's another reason to go ahead and have a flu vaccination," he added in an interview.

If the findings are borne out by future studies, then it could lead to changes in the recommended timing and indications for flu shots, the researchers concluded.

It's thought that an inflammation process related to flu starts to affect coronary blood vessels, which as a result of the flu are more likely to rupture and cause a heart attack, Siriwardena said.

"I think this is a very interesting piece of evidence that the flu may be related to heart attack, and by preventing flu we can prevent as many as one in five heart attacks," said Dr. Chi-Ming Chow, a cardiologist at St. Michael's Hospital in Toronto, commenting on the study.

The findings are not proof of a link, but they offer another piece of evidence on the benefits of flu shots for people with chronic illness and others who may not be aware of their heart health, said Dr. Robert Strang, Nova Scotia's chief public health officer.

"In general, our message to the public is that there's lots of evidence of flu vaccine preventing a whole range of health outcomes," Strang said.

Other ways of avoiding flu, such as handwashing or staying away from crowds, could also play a role in preventing heart attacks.

The study was funded by the U.K.'sNational Institute for Health Research. The authors did not declare any potential conflicts of interest.