Flu triggers heart attacks, study shows

WASHINGTON (Reuters) - Influenza can trigger deadly heart attacks, researchers said on Wednesday in a study that supports what experts have long believed -- flu can kill people even if they do not die directly from the flu.

Their report shows that the seasonal virus can worsen heart disease and that deaths from heart attacks and heart disease are far more common during flu season.

This can add up to 90,000 extra deaths a year in the United States alone, said Dr. Mohammad Madjid of the University of Texas-Houston, who led the study.

Writing in the European Heart Journal, the researchers said their findings add to a growing list of reasons why people should get annual flu shots. They also said people with heart disease should stick to their medications religiously.

"Our research has shown that influenza epidemics are associated with a rise in coronary deaths," Madjid said in a statement. "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," he said.

Flu viruses change every year and several are usually circulating in any given season, making the risk of flu high for most people.

"Between 10 and 20 percent of people catch flu every year and I have estimated that we can prevent up to 90,000 coronary deaths a year in the (United States) if every high-risk patient received an annual flu vaccination," Madjid said.

Madjid and colleagues at the Influenza Research Institute in St. Petersburg, Russia, studied autopsy reports on people who died from heart disease in that city from between 1993 and 2000.

"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," Madjid said.

They found that 11,892 people died from heart attacks and 23,000 died from chronic heart disease.

Deaths from heart attacks increased by a third in flu epidemic weeks compared to non-epidemic weeks and the chances of dying from chronic heart disease increased by a tenth.

"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." Madjid said.

"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."