Flu increases heart attack and stroke risk, study claims

Respiratory infections cause inflammation, while the flu virus and pneumonia can damage heart muscle

People who have had flu are up to six times more likely to suffer from a heart attack or stroke in the days after infection, new research published today states.

Those who have had pneumonia face a similar increased risk of a cardiovascular event occurring in the week after infection, while the risk of having a stroke is increased for one month, according to the study.

The research, published in the European Respiratory Journal, is the largest study to look at the risk of heart attacks and strokes due to specific respiratory infections.

Using national infection surveillance data from the Scottish Morbidity Record, researchers from the London School of Hygiene and Tropical Medicine identified 1,227 adults with a first heart attack and 762 with a first stroke who also had a respiratory virus or bacteria infection between 2004 and 2014.

The findings suggest that getting the influenza and pneumococcal vaccines have a role in preventing heart attack and stroke, as well as preventing infection in the first place.

Respiratory infections are thought to increase the risk of heart attack and stroke by causing inflammation, which can lead to the development of blood clots. The influenza virus and S.pneumoniae, the most common pneumonia causing bacteria, can also damage heart muscle.

Public health problems

Commenting on the results, lead researcher Dr Charlotte Warren-Gash, said: “Heart disease, strokes and lower respiratory infections have been the three leading causes of death globally for over 15 years, and are important public health problems that affect large numbers of people worldwide.”

She added: “In Scotland, among those aged 75 years and above, about two in 10,000 people have a heart attack each week. Our analysis found this figure rose to 10 in 10,000 in the week after having a respiratory infection.”

While past their peak, influenza viruses continue to circulate in Ireland. According to the latest flu activity report from the European Centre for Disease Prevention and Control (ECDC) there are excess winter deaths in several countries, especially following influenza A(H3N2) infection. Influenza A and B are co-circulating in Europe; the majority of severe cases reported this season have been due to influenza B infection in people aged over 15.