Research led by a Minneapolis pharmacist has found a link between influenza and hospitalizations for heart failure, building the case for more adults getting their flu shots.
Studying influenza seasons between 2010 and 2014, the group of researchers found that heart failure-related hospitalizations rose by 24 percent in those months when clinics reported 5 percent bumps in flu activity.
The study is one of the first to establish an association between influenza and heart failure — though prior research has shown more heart attacks in severe flu seasons, said Orly Vardeny, a pharmacist with the University of Minnesota and the Minneapolis Veterans Medical Center.
"The purpose really is to strengthen the rationale for people getting vaccinated, especially people who are vulnerable, like those with heart disease," she said.
An estimated 5.7 million Americans have heart failure, a condition in which the heart can't pump enough blood and oxygen to keep up with the body. The study found only an association between influenza and heart failure; why the viral infection might contribute to more cardiac-related hospitalizations is unclear.
Influenza is believed to cause more heart attacks, which are different from heart failure and involve blockages that lead to sudden damage to the heart muscle. The virus prompts inflammation and the release of chemicals that can lead to a heart attack. The same process could contribute to complications from heart failure, but Vardeny said it's possible that influenza forces the body into overdrive and that weak hearts simply fall behind.
"There's an increased metabolic demand when someone has influenza," she said. "Someone with heart failure just doesn't have the reserves to accommodate that."
Vardeny and researchers from four other states and Canada published their results this week in JAMA Cardiology, a medical journal. Their study drew on flu surveillance over four seasons and data from a prior heart study that involved patients from Minneapolis and from Mississippi, North Carolina and Maryland.
Vardeny said she predicted that older people with heart failure would suffer more hospitalizations in bad flu seasons, but the research found that age didn't matter. "When someone has heart disease, regardless of age, they are vulnerable to complications from influenza," she said.
Vardeny said she hopes the results persuade more people to get flu shots.
Jeremy Olson • 612-673-7744