Increased Influenza-like Illness Activity Linked to Heart Failure Hospitalizations

Influenza may contribute to an increased risk of heart failure (HF) and myocardial infarction (MI) in the general public, according a new study published in JAMA Cardiology.

In this community surveillance, population-based study, researchers sampled four US communities and collected data from 451,588 adults aged 35 to 84 residing in the Atherosclerosis Risk in Communities (ARIC) from annual cross-sectional stratified random samples of hospitalizations for HF or MI that took place from October 2010 to September 2014. The four sampled communities were geographically diverse and included Jackson, Mississippi, some city suburbs of Minneapolis, Minnesota, and two rural communities: Forsyth County, North Carolina, and Washington County, Maryland.

The study’s exposures consisted of monthly influenza activity, defined as the percentage of patient visits to clinicians for influenza-like illness by state, as reported by the Centers for Disease Control (CDC) and Prevention Surveillance Network. The main outcomes and measures were the monthly frequency of MI hospitalizations (n=3,541) and HF hospitalizations (n=4,321) collected via community surveillance and examined as part of the study.

Flu Activity Tied to HF Increases

Results of the study showed a 5% monthly absolute increase in influenza activity was correlated with a 24% increase in HF hospitalization rates, standardized to the total population in each community, within the same month after adjusting for region, season, race/ethnicity, sex, age, and number of MI/HF hospitalizations from the month before (incidence rate ratio=1.24; 95% CI, 1.11 to 1.38; P <0.001), while overall influenza activity was not greatly associated with MI hospitalizations (incidence rate ratio=1.02; 95% CI, 0.90 to 1.17; P =0.72). Moreover, influenza activity in the months before hospitalization was not associated with either outcome. The researchers model suggests that in a month with elevated influenza activity, approximately 19% of HF hospitalizations (95% CI, 10% to 28%) could be attributable to influenza.

“These data suggest that while hospitalizations for influenza and pneumonia, and deaths associated with these, are greatest during severe influenza seasons, acute CV events are also likely increased during periods of peak influenza activity,” researchers wrote in discussing the study results. “Of note, the A/H3N2 virus, which is associated with more severe morbidity and mortality, was the predominant strain that circulated during the 2012 to 2013 season.”

The researchers feel these findings will affect the way influenza is explored and treated as a contributing factor to HF and said that these data “have implications for surveillance strategies aimed at identifying influenza as a cause of hospitalization in high-risk CV patients and vaccination strategies to mitigate this risk.”