biostudies-literatureUnknown12Langhammer A<h4>Background</h4>Population based studies are important for prevalence, incidence and association studies, but their external validity might be threatened by decreasing participation rates. The 50 807 participants in the third survey of the HUNT Study (HUNT3, 2006-08), represented 54% of the invited, necessitating a nonparticipation study.<h4>Methods</h4>Questionnaire data from HUNT3 were compared with data collected from several sources: a short questionnaire to nonparticipants, anonymous data on specific diagnoses and prescribed medication extracted from randomly selected general practices, registry data from Statistics Norway on socioeconomic factors and mortality, and from the Norwegian Prescription Database on drug consumption.<h4>Results</h4>Participation rates for HUNT3 depended oBMC medical research methodology143https://www.ebi.ac.uk/biostudies/studies/S-EPMC3512497biostudies-literatureThe HUNT study: participation is associated with survival and depends on socioeconomic status, diseases and symptoms.PMC3512497Krokstad SRomundstad PLanghammer AHolmen JHeggland JfalseThe HUNT study: participation is associated with survival and depends on socioeconomic status, diseases and symptoms.<h4>Background</h4>Population based studies are important for prevalence, incidence and association studies, but their external validity might be threatened by decreasing participation rates. The 50 807 participants in the third survey of the HUNT Study (HUNT3, 2006-08), represented 54% of the invited, necessitating a nonparticipation study.<h4>Methods</h4>Questionnaire data from HUNT3 were compared with data collected from several sources: a short questionnaire to nonparticipants, anonymous data on specific diagnoses and prescribed medication extracted from randomly selected general practices, registry data from Statistics Norway on socioeconomic factors and mortality, and from the Norwegian Prescription Database on drug consumption.<h4>Results</h4>Participation rates for HUNT3 depended o2012-01-01T00:00:00Z2012 Sep2025-04-19T12:22:47.163Z2019-03-27T01:01:20ZS-EPMC35124972297874910.1186/1471-2288-12-143