Influenza infections can be especially troublesome for people with cardiovascular disease, increasing the rate of heart attacks by as much as 50%, British researchers report online today in the journal Lancet Infectious Diseases. Vaccination against influenza can reduce the incidence of heart attacks in at-risk people, they found, but usually only 30% to 40% of patients actually receive the seasonal flu vaccine. The results may be even more dismal this year when patients will require vaccination against the seasonal flu and the pandemic H1N1 virus, commonly known as swine flu.
Researchers from University College London and the London School of Hygiene and Tropical Medicine reviewed 42 papers, published between 1932 and 2008, that covered 39 studies examining the link between flu and heart attacks. All the studies consistently showed a rise in heart attacks during periods when influenza viruses were circulating, with the increase ranging from 35% to 50%, and a weaker association with death from heart attacks. Four of eight observational studies and two small clinical trials also showed that vaccination lowered the rate of heart attacks.
"The message here is so strong and logical that it's hard for us to ignore," Dr. Ralph Brindis, vice president of the American College of Cardiology, told the Associated Press.
Influenza viruses cause inflammation throughout the body, including in the heart and blood vessels. That can lead to clots breaking off and lodging in the heart, where they cause heart attacks. The best protection: Get your swine flu shot.