Obesity and Swine Flu: Examining the Potential Link

By Anna Muldoon, Member, The George Washington University’s Research Team for the STOP Obesity Alliance; Reviewed by Morgan Downey, JD, Policy Advisor

Recent news reports have made much of the May 18, 2009 article in Morbidity and Mortality Weekly Report (MMWR) showing a link between obesity hospitalization with H1N1 influenza¹, known to most as swine flu.  Although the number of cases available for study at the time was relatively small, this correlation is supported by earlier research on respiratory infections and obesity.  Several studies have found a correlation between obesity and increased rates of respiratory infections acquired both inside and outside the hospital^{2, 3}.  Explanations for the correlation range from increased intra-abdominal pressure to the effect of leptin resistance on the immune system, including physical, chemical and behavioral explanations that combine to provide a clear mechanism for the increase².  

At a moment when H1N1 flu is rapidly spreading across the world, any factor that increases hospitalization rates must be considered seriously as we plan for both the coming flu season and the future.  It is near impossible that any program could reduce the prevalence of obesity rapidly enough to make a difference in hospitalizations if H1N1 returns in the winter.  At the same time, the as yet mild first appearance of H1N1 has shown the remaining flaws in our planning for both flu pandemics and other potential health care emergencies.   Strengthening our pandemic preparedness for the future must include an analysis of the factors that make a population vulnerable as well as ways to mitigate those vulnerabilities.  In the case of respiratory illness, our current high rates of obesity are clearly one of those vulnerabilities.

If we are to successfully combat the spread of emerging diseases, including novel influenzas, we must focus on improving population health overall and reducing known risk factors for serious infectious illness.  While obesity is frequently linked to chronic conditions such as diabetes and asthma, its links to community acquired infections are rarely discussed.  The body of research on respiratory infections and obesity is not large and influenza in particular has not been widely studied in this population.  In order to plan appropriately, this area of research needs to be expanded.  Programs that reduce obesity in the population would also likely have a positive effect on the rate of hospitalization in individuals who do not have other complicating conditions.  In this case, combating obesity can clearly be framed in terms of emergency preparedness and national pandemic planning, which may encourage political and social buy-in to obesity reducing programs.

1.       “Hospitalized Patients with Novel Influenza A (H1N1) Virus Infection – California, April-May, 2009”.  MMWR Early Release.  May 18, 2009.  58 (Early Release): 1-5.

2.       Matthew E. Falagas and Maria Kompoti. “Obesity and Infection”.  Lancet Infectious Disease: 2006, Iss. 6.  438-446.

3.       Grant V. Bochicchio et al. “Impact of Obestiy in the Critically Ill Trauma Patient: A Prospective Study”.  Journal of the American College of Surgeons: 2006.  Vol. 203, No. 4.  533-538.