title: Obesity as a risk factor for severe influenza-like illness.
abstract: BACKGROUND
  Obesity was recognized as in independent risk factor for influenza during the 2009 H1N1 influenza pandemic.
  
  
  OBJECTIVE
  We evaluated the association between body mass index (BMI) and influenza-like illness (ILI) during two non-pandemic influenza seasons (2003-2004 and 2004-2005) and during the spring and fall waves of the 2009 H1N1 pandemic.
  
  
  METHODS
  Adults with severe (inpatient) and mild (outpatient) ILI were compared to those without ILI using a case-cohort design. The study was nested among those insured by a single health insurance company, receiving care from a large multispecialty practice. Data were collected from insurance claims and the electronic health record. The primary exposure was obesity (BMI ≥ 30·0 kg/m(2) ).
  
  
  RESULTS
  Across three seasons, the crude and adjusted ORs for obesity and severe ILI were 1·65 (95% CI 1·31, 2·08) and 1·23 (95% CI 0·97, 1·57), respectively. An association was observed for those aged 20-59 years (adjusted OR 1·92, 95% CI 1·26, 2·90), but not for those 60 and older (adjusted OR 1·08, 95% CI 0·80, 1·46). The adjusted ORs for obesity and severe ILI in 2003-2004, 2004-2005, and during H1N1 were 1·14 (95% CI 0·80, 1·64), 1·24 (95% CI 0·86, 1·79), and 1·76 (95% CI 0·91, 3·42), respectively. Among those with a Charlson Comorbidity Index score of zero, the adjusted ORs for 2003-2004, 2004-2005, and H1N1 were 1·60 (95% CI 0·93, 2·76), 1·43 (95% CI 0·80, 2·56), and 1·90 (95% CI 0·68, 5·27), respectively.
  
  
  CONCLUSIONS
  Our results suggest a small to moderate association between obesity and hospitalized ILI among adults.
authors: Bureau of Infectious Disease, Massachusetts Department of Public Health, Jamaica Plain, MA, USA.
authors: Noelle M
authors: NM
authors: Cocoros
authors: Timothy L
authors: TL
authors: Lash
authors: Alfred
authors: A
authors: DeMaria
authors: Michael
authors: M
authors: Klompas
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015992:Body Mass Index; D016022:Case-Control Studies; D005260:Female; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D007251:Influenza, Human / Q000453:epidemiology* / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000150:complications*; D012307:Risk Factors; D055815:Young Adult
keywords: BMI; influenza; obesity
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