Obesity is associated with higher risk of intensive care unit admission and death in influenza A (H1N1) patients: a systematic review and meta-analysis

Obes Rev. 2011 Aug;12(8):653-9. doi: 10.1111/j.1467-789X.2011.00864.x. Epub 2011 Apr 4.


The aim of this study was to assess the association between obesity and the risk of intensive care unit (ICU) admission and death among patients hospitalized for influenza A (H1N1) viral infection. A systematic review of the Medline and Cochrane databases using 'obesity', 'hospitalization', 'influenza A viral infection', various synonyms, and reference lists of retrieved articles from January 2009 to January 2010. Studies comparing the prevalence of obesity among patients with confirmed infection for influenza A virus and who were either hospitalized or admitted to ICU/died were included. A total of 3059 subjects from six cross-sectional studies, who were hospitalized for influenza A (H1N1) viral infection, were included in this meta-analysis. Severely obese H1N1 patients (body mass index ≥ 40 kg m(-2), n = 804) were as twice as likely to be admitted to ICU or die (odds ration: 2.01, 95% confidence interval: 1.29-3.14, P < 0.002) compared with H1N1 patients who were not severely obese. Having a body mass index ≥ 30 kg m(-2) was similarly associated with a more than twofold increased risk of ICU admission or death although this did not reach statistical significance (2.14, 0.92-4.99, P < 0.07). This meta-analysis supports the view that obesity is associated with higher risks of ICU admission or death in patients with influenza A (H1N1) infection. Therefore, morbid obese patients should be monitored more intensively when hospitalized.

Publication types

  • Meta-Analysis
  • Review
  • Systematic Review

MeSH terms

  • Body Mass Index
  • Cross-Sectional Studies
  • Hospitalization*
  • Humans
  • Influenza A Virus, H1N1 Subtype*
  • Influenza, Human / complications
  • Influenza, Human / mortality*
  • Influenza, Human / physiopathology*
  • Intensive Care Units*
  • Obesity / complications*
  • Obesity, Morbid / complications
  • Risk Factors