What Is the Accurate Prevalence of Obesity in Sweden in the 21st Century? Methodological Experiences From the Skaraborg Project.

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 and Procedures: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).Discussion: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.Obesity (2008) doi:10.1038/oby.2007.134