When the number of reported flu cases goes up, so does the number of hospitalizations for heart failure.
A study in JAMA Cardiology used data on 451,588 people, ages 35 to 84, in four geographic areas over four flu seasons, from 2010 to 2014. The researchers randomly sampled 2,042 hospitalizations for heart failure and 1,599 for heart attack. To track flu activity, they used surveillance data from the Centers for Disease Control and Prevention.
After adjusting for region, season, race and ethnicity, age and other variables, they found that for every monthly 5 percent increase in visits to clinicians for flulike symptoms during flu season, there was a 24 percent increase in hospitalizations for heart failure. There was a trend indicating an association with heart attack as well, especially during seasons with the virulent H3N2 subtype of the virus, but that trend did not reach statistical significance.
The researchers calculated that in months with high influenza rates, about 19 percent of hospitalizations for heart failure could be attributable to influenza alone.
“Influenza is not just a one- or two-week illness with some respiratory symptoms,” said the senior author, Orly Vardeny, an associate professor at the Minneapolis VA Medical Center. “We need to think about it affecting the person’s underlying health conditions as well. The best way to prevent the flu is to get the flu shot.”