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Another Reason to Get Your Flu Shot
Abstract & Commentary
By Barbara A. Phillips, MD, MSPH, Professor of Medicine, University of Kentucky; Director, Sleep Disorders Center, Samaritan Hospital, Lexington. Dr. Phillips reports no financial relationship to this field of study.
Synopsis: There is a surge of coronary deaths following influenza epidemics, which strengthens the importance of flu vaccinations for those at risk for cardiovascular events.
Source: Mohammad M, et al. Influenza epidemics and acute respiratory disease activity are associated with a surge in autopsy-confirmed coronary heart disease death; results from 8 years of autopsies in 34, 892 subjects. Eur Heart J. 2007; epub ahead of print April 17.
This study is a collaborative effort of the Texas Heart Institute and the Influenza Research Institute of St Petersburg, Russia. The authors focused on deaths from St Petersburg, Russia during 1993-2000. Using data from St Petersburg's Influenza Research Center, which defined when epidemics were occurring based on pre-determined thresholds, the investigators reviewed autopsy reports from 34,892 subjects who died as a result of the flu (the autopsy rate in St Petersburg is over 70%!). They compared the average within-epidemic mortality to the average off-epidemic mortality for both respiratory and coronary heart disease deaths. There were 9 flu epidemics during the study period. Each influenza epidemic was associated with an increase in cardiac mortality. During this 8 year period, 11,892 people died of acute MI and 23,000 died of chronic ischemic heart disease. The marked rise in coronary deaths during each flu epidemic generally coincided with a rise in acute respiratory disease deaths. The excess in cardiac deaths persisted for about 10 weeks, with maximum mortality rates for 2 weeks on either side of the peak of acute respiratory deaths. Deaths affected genders equally, but older people disproportionately. The authors were able to model a prediction of future cardiac deaths associated with flu epidemics in St Petersburg.
This article first got my attention when it was covered by my local newspaper, which noted, "Study links flu, heart attacks." People are interested in anything to do with the flu these days, with dire predictions that the next flu epidemic is not a matter of "if" but "when." In truth, large epidemiologic studies have already linked flu with myocardial infarction (MI) and demonstrated that influenza vaccination can reduce the risk of influenza-associated MI.1-4 What is new about the current study is the precision of the methods used, including autopsy verification of cause of death. Although the flu shot is indicated for those at risk for cardiac disease,5 both public perception and medical practice have de-emphasized this indication. In their introduction, the authors point out that about twice as many people die of cardiac causes than pulmonary causes during influenza epidemics. Perhaps the biggest take home message here is that flu shots are not just for those with lung disease, but also for those at risk for cardiovascular disease.
1. Couch RB. N Engl J Med. 2000;343:1778-1787.
2. Madjid M, Casscells SW. Lancet. 2004;364:1309.
3. Eickhoff TC, et al. JAMA. 1961;176:776-782.
4. Naghavi M, et al. Circulation. 2000;102:3039-3045.
5. Smith SC, et al. Circulation. 2006;113:2363-2372.