title: Investigating obesity as a risk factor for influenza-like illness during the 2009 H1N1 influenza pandemic using the Health Survey for England.
abstract: Following the 2009 H1N1 influenza pandemic, obesity was shown to be associated with severe influenza outcomes. It remains unclear whether obesity was a risk factor for milder influenza-like illness (ILI).
  
  
  
  To determine whether obesity was associated with an increased risk of self-reported ILI during the 2009 H1N1 influenza pandemic using Health Survey for England (HSE) 2010 cross-sectional data.
  
  
  
  This study used HSE data collected from English households between January and December 2010. Weight and height measurements were taken by trained fieldworkers to determine obesity. ILI was defined as a positive response to the question "Have you had a flu-like illness where you felt feverish and had a cough or sore throat?" with illness occurring between May and December 2009. Multivariable logistic regression was used to evaluate the association between obesity and ILI.
  
  
  
  The study comprised 8407 participants (6984 adults, 1436 children), among whom 24.7% (95% CI: 23.6-25.9) were classified as obese. Of obese participants, 12.8% (95% CI: 11.1-14.8) reported ILI compared to 11.8% (95% CI: 10.8-12.8) of non-obese participants. The adjusted OR for ILI associated with obesity was 1.16 (95% CI: 0.98-1.38, P=.093). For adults and children, the adjusted ORs were 1.16 (95% CI: 0.97-1.38, P=.101) and 1.26 (95% CI: 0.72-2.21, P=.422), respectively.
  
  
  
  Household survey data showed no evidence that obesity was associated with an increase in self-reported ILI during the 2009 H1N1 influenza pandemic in England. Further studies using active prospective ILI surveillance combined with laboratory reporting would reduce bias and improve accuracy of outcome measurements.
authors.affiliation: London School of Hygiene & Tropical Medicine, London, UK.
authors.forename: Rachel
authors.initials: R
authors.lastname: Murphy
authors.affiliation: London School of Hygiene & Tropical Medicine, London, UK.|Institute of Health Informatics, University College London, London, UK.
authors.forename: Ellen B
authors.initials: EB
authors.lastname: Fragaszy
authors.affiliation: Institute of Health Informatics, University College London, London, UK.
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Hayward
authors.affiliation: Institute of Health Informatics, University College London, London, UK.
authors.forename: Charlotte
authors.initials: C
authors.lastname: Warren-Gash
mesh_terms: D000293:Adolescent; D000328:Adult; D015992:Body Mass Index; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D004739:England / Q000453:epidemiology; D005191:Family Characteristics; D005260:Female; D006306:Health Surveys; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D053118:Influenza A Virus, H1N1 Subtype / Q000472:pathogenicity*; D007251:Influenza, Human / Q000453:epidemiology* / Q000209:etiology / Q000821:virology; D008297:Male; D009765:Obesity / Q000150:complications* / Q000453:epidemiology / Q000821:virology; D058873:Pandemics / Q000517:prevention & control; D011446:Prospective Studies; D012307:Risk Factors; D057566:Self Report; D055815:Young Adult
keywords: Health Survey for England; body mass index; influenza-like illness; obesity