Robust interventional studies needed to establish causality, directionality
A study of > 450,000 adults has “confirmed the long-held notion” that flu and heart failure are connected. The Atherosclerosis Risk in Communities study (ARIC), led by a VA researcher, found influenza significantly increased the risk of hospitalization for heart failure.
Every flu season about 36,000 people die, and > 200,000 are hospitalized due to flu, which is known to be associated with a higher risk of cardiovascular events. Several mechanisms likely contribute: Some form of immunocompromise is thought to be a key link. But few studies, the researchers note, have explored the temporal association between influenza activity and hospitalizations, particularly those caused by heart failure.
In ARIC, the researchers analyzed hospitalization data for adults aged 35 to 84 years between 2010 and 2014 in geographically diverse communities in Mississippi, Minnesota, North Carolina, and Maryland. They correlated those data with reports of influenza activity from the CDC Surveillance Network.
A 5% monthly increase in influenza activity was associated with a 24% relative increase in heart failure hospitalization rates. Myocardial infarction hospitalizations did not rise significantly. The most pneumonia and influenza-associated deaths were during the 2012-2013 season, when influenza-like illness (ILI) activity was highest, and the fewest deaths occurred during 2011-2012, when ILI activity was lowest. The model suggests that in a month with high influenza activity, about 19% of hospitalizations could be attributable to influenza, the researchers say.
“The study’s findings support VA’s aggressive effort every year to provide veterans with influenza vaccine,” said VA Secretary Robert Wilkie. Although the flu season is winding down, he added, it is not too late for veterans—and others—to get vaccinated.