Association may provide another reason to get vaccinated
Heavy flu months are also likely to see a big uptick in heart failure hospitalizations, the population-based Atherosclerosis Risk in Communities (ARIC) study found.
A monthly 5% absolute increase in influenza activity was linked with 24% more heart failure (HF) hospitalizations (P<0.001) within the same month following multivariable adjustment, reported Scott Solomon, MD, of Brigham and Women's Hospital in Boston, and colleagues in JAMA Cardiology.
The flu-activity association didn't extend into the several months prior to hospitalization, but an estimated 19% of HF hospitalizations (95% CI 10%-28%) could be attributed to influenza in a given month with substantial influenza activity.
Prior research has shown that influenza infection is linked with a greater risk of cardiovascular events. Numerous investigations have indicated that during times when influenza was circulating there was an increase in acute MI and cardiovascular mortality. There are few investigations that have looked into the temporal relationship between hospitalizations, especially those resulting from HF and influenza activity, the investigators noted.
"Addressing influenza activity may be valuable in efforts to prevent HF hospitalizations," the researchers wrote.
This study reinforces and extends the existing literature, noted William Schaffner, MD, of Vanderbilt University Medical Center in Nashville, Tennessee. "In recent years, we have become increasingly aware that influenza has effects beyond the lung. And indeed, there are several papers now that indicate that influenza creates an inflammatory response that actually predisposes people to heart attacks and strokes," he told MedPage Today.
"We need to emphasize much more strongly the importance of all persons with chronic illnesses, including heart disease of any kind, to get vaccinated against influenza each and every year. The hope, of course, is that we can prevent or reduce the severity of influenza, and by that means reduce the occurrence of heart failure and also heart attacks," Schaffner continued.
Another implication is in assessing for influenza infection in patients admitted for decompensated CHF without a clear other cause, commented Ajith Nair, MD, of Baylor College of Medicine in Houston, who was not involved in the study.
The ARIC analysis also showed a weak, nonsignificant association between influenza activity overall and myocardial infarction (MI) hospitalizations.
The researchers noted that prior studies have found MI risk was greater in the week following infection but decreased over time.
"Therefore, it may not be possible to discern an association that occurs within a shorter time frame using event counts that were aggregated at the month level," they wrote. "The lack of a clear association in our analysis is likely a function of power and insufficient temporal resolution to detect the association between influenza infection and MI."
Solomon's group evaluated 451,588 adults in a random sample of HF and MI hospitalizations in the four U.S. communities where ARIC performs community surveillance. The cohort was 53.3% female, 57.4% white, and ranged in age from 35 to 84 years.
About 45% of the sampled patients were hospitalized for MI, and about 47% for HF.
Monthly influenza activity data came from the CDC Surveillance Network, defined by the percentage of patient visits to sentinel practitioners for influenza-like sicknesses by state.
Solomon acknowledged the study's limitations in relying on surveillance from only four communities and in having limited information on the individuals who were hospitalized. "We don't know who was or was not vaccinated. We also lacked greater than about several weeks of temporal resolution, so we could only relate influenza activity to hospitalizations within the same month, and not at the weekly or daily level," Solomon told MedPage Today.
"Further studies are necessary to determine whether strategies to reduce influenza activity at the population level reduce the incidence of MI and HF hospitalizations," the researchers concluded.
The Atherosclerosis Risk in Communities Study has been funded by the National Heart, Lung, and Blood Institute, the National Institutes of Health, and the Department of Health and Human Services.
Solomon disclosed relationships with Alnylam, Amgen, AstraZeneca, Bellerophon, Bayer, BMS, Celladon, Cytokinetics, Eidos, Gilead, GSK, Ionis, Lone Star Heart, Mesoblast, MyoKardia, the National Institutes of Health/National Heart, Lung, and Blood Institute, Novartis, Sanofi Pasteur, Theracos, Akros, Cardior, Corvia, Ironwood, Merck, Roche, Takeda, Quantum Genetics, Cardurion, AOBiome, Janssen, Cardiac Dimensions, and Tenaya.
Schaffner disclosed relationships with Merck, Pfizer, Shionogi, SutroVax, and Seqirus.
Source Reference: Kytömaa S, et al "Association of influenza-like illness activity with hospitalizations for heart failure: the atherosclerosis risk in communities study" JAMA Cardiol 2019; DOI: 10.1001/jamacardio.2019.0549.
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