title: What is the accurate prevalence of obesity in Sweden in the 21st century? Methodological experiences from the skaraborg project.
abstract: OBJECTIVE
  To examine the impact of non-response to self-reported body weight and height in health questionnaires for the estimation of obesity prevalence.
  
  
  METHODS
  A cross-sectional population-based health survey in the community ofVara with 16,009 residents (in year 2002) in South-western Sweden. Participants randomly selected in strata by sex and age among residents being 30-74 years old were consecutively invited to the local health care center for a health examination, including two visits. Self-reported information on body weight and height were obtained by health questionnaires at the first visit, and measured information on both variables at the second visit. For this study 1,809 subjects (904 men and 905 women) completed both visits (participation rate 81%), and a nurse measured body weight and height of all at visit two. Participants not self-reporting body weight and/or height at the first visit were defined as non-responders.
  
  
  RESULTS
  Both male and female non-responders were significantly older than responders. Female non-responders had significantly higher BMI (29.8 +/- 5.8 kg/m(2)) than female responders (26.6 +/- 5.3 kg/m(2)), (P < 0.001). No similar findings were seen in men. Non-responders were more likely to be obese than responders both in men (odds ratio (OR) 2.06, 95% confidence interval (CI) 1.03-4.11) and in women (OR 2.24, 95% CI 1.25-4.02).
  
  
  CONCLUSIONS
  Non-responders to self-reported body weight and height in health questionnaires contribute to the underestimation of obesity. Measured body weight and height are to prefer when describing the accurate prevalence of obesity in populations.
authors.affiliation: Skaraborg Institute, Skövde, Sweden.
authors.forename: Maria
authors.initials: M
authors.lastname: Nyholm
authors.forename: Bo
authors.initials: B
authors.lastname: Gullberg
authors.forename: Lennart
authors.initials: L
authors.lastname: Råstam
authors.forename: Ulf
authors.initials: U
authors.lastname: Lindblad
mesh_terms: D000328:Adult; D017677:Age Distribution; D000368:Aged; D001827:Body Height; D001835:Body Weight; D004812:Epidemiologic Methods; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000453:epidemiology*; D015995:Prevalence; D015203:Reproducibility of Results; D017678:Sex Distribution; D011795:Surveys and Questionnaires / Q000592:standards*; D013548:Sweden / Q000453:epidemiology