Influenza Activity Associated With Heart Failure Hospitalization Risk

An increase in influenza illness activity is associated with an increase of hospitalizations for heart failure occurring within the same month, according to a study published in JAMA Cardiology.

The researchers of this population-based study sought to explore the temporal association between influenza activity and hospitalization due to heart failure and myocardial infarction.

The study sample included 451,588 adults aged 35 to 84 years residing in communities surveilled in the Atherosclerosis Risk in Communities (ARIC) study, from which the investigators analyzed data from annual samples of hospitalizations from 4 US communities between October 2010 and September 2014.

The primary exposure of interest was monthly influenza activity, which was measured by the percentage of patients who visited clinicians for influenza-like illness, reported by the Centers for Disease Control and Prevention Outpatient Influenza-like Illness Surveillance Network.

Data on the monthly frequency of hospitalizations for myocardial infarction (n=3541) and heart failure (n=4321) were extracted from the surveillance component of the ARIC study. The investigators used a Poisson regression model to analyze the association between monthly influenza activity and hospitalizations; incident rates were standardized to the population of each community, and analyses were adjusted for region, season, race/ethnicity, gender, age, and the number of hospitalizations associated with myocardial infarction and heart failure from the month before.

In standardized analyses, a 5% absolute increase in influenza activity per month was associated with a 24% increase in heart failure hospitalization rates within the same month (incident rate ratio [IRR] 1.24; 95% CI, 1.11-1.38; P <.001), while no significant association was observed between influenza-like illness activity and myocardial infarction hospitalization rates (IRR 1.02; 95% CI, 0.90-1.17; P =.72), which were examined over 4 seasons.

When analyzing patient visits for influenza-like illness up to 6 months prior to hospitalization, influenza activity was not associated with either heart failure or myocardial infarction.

Limitations to the study included lack of patient-level data regarding influenza or vaccination status of those hospitalized for myocardial infarction or heart failure and the inability to analyze influenza severity in association with hospitalization. It is possible that a different infectious cause or virus that cocirculates with influenza accounted for higher hospitalization rates.

The researchers indicated that in months with high influenza-like illness activity, 19% of heart failure hospitalizations within the same month could be attributed to influenza. However, influenza activity in the months prior to exposure did not have a temporal association with hospitalization rates.  

Reference

Kytömaa S, Hegde S, Claggett B, et al. Association of influenza-like illness activity with hospitalizations for heart failure: the atherosclerosis risk in communities study [published online March 27, 2019]. JAMA Cardiol. doi: 10.1001/jamacardio.2019.0549