Influenza vaccinations could prevent thousands of deaths from heart disease
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Dr. Mohammad Madjid advises his cardiology patients to get flu vaccinations every year.
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People who are at risk of heart disease should receive the influenza vaccine every autumn. New research shows that influenza epidemics are associated with a rise in deaths from heart disease and that flu can actually trigger the heart attacks that result in death.
However, only about 60 percent of people in the U.S. who ought to have a flu vaccination actually have one, said Mohammad Madjid, M.D., a cardiologist who specializes in atherosclerosis research at the Texas Heart Institute and The University of Texas Health Science Center Houston.
“Our research has shown that influenza epidemics are associated with a rise in coronary deaths. This calls for more intensive efforts to increase the vaccination rate in people at risk of coronary heart disease. This may be especially important in an influenza pandemic when we would expect to see high mortality among the elderly and those suffering from heart problems or who have multiple coronary risk factors,” said Dr. Madjid. “Between 10 and 20 percent of people catch the flu every year, and I have estimated that we can prevent up to 90,000 coronary deaths a year in the U.S. if every high risk patient received an annual flu vaccination.”
Dr. Madjid worked with colleagues in the U.S. and in St. Petersburg in the Russian Federation to investigate deaths between 1993 and 2000 in St. Petersburg that had been shown by autopsy reports to be due to coronary heart disease.
“This was a population where only a small minority were receiving flu vaccines or statin drugs, so this enabled us to see what happened naturally in the absence of these medicines,” said Prof Madjid. “Relying on autopsy reports rather than death certificates enabled us to be much more accurate about the cause of death, because doctors often neglect to list flu on a death certificate if their patients have died from a heart attack and, conversely, heart attack symptoms can be missed in patients suffering from flu and pneumonia.”
They found that 11,892 people died from acute myocardial infarction (AMI) (47.8% men and 52.2% women), and 23,000 died from chronic ischemic heart disease (IHD) (40.1% men and 59.9% women). The peaks in deaths from both AMI and IHD coincided with the times when influenza epidemics and acute respiratory disease, which often accompanies flu, were at their height. They found that the chances of dying from AMI increased by a third in epidemic weeks, compared to non-epidemic weeks, and the chances of dying from IHD increased by a tenth. This was the same for both men and women and in different age groups.
Researchers believe that flu causes an acute and severe inflammation in the body which, in some patients, can destabilize atherosclerotic plaques in coronary arteries and cause heart attacks.
Most people in Western countries live with different stages of atherosclerosis and many will never show any symptoms. However, in some patients the stable atherosclerotic plaques undergo sudden changes, mainly due to exaggerated inflammation, leading to rupture of these vulnerable plaques and subsequent formation of clots resulting in heart attacks.
“This study shows that flu is an important trigger of heart attacks because flu is a severe infection, with high incidence rates and is readily preventable. Therefore, our results give us a new tool for preventing heart attacks,” said Dr. Madjid. “If people can recognize that the flu vaccine has specific cardioprotective effects, then high-risk people will be more likely to make sure that they receive the influenza vaccine every year.”
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Updated October 2007
