Between August 1995 and June 1997, all inhabitants aged 20 years or older in Nord-Trøndelag County were invited to participate in the Nord-Trøndelag Health Study (HUNT). In brief, two questionnaires including more than 200 health related questions were administrated to the participants. The population in Nord-Trøndelag County was ethnically homogenous (less than 3% of subjects were of non-Caucasian ethnicity), making it suitable for epidemiological genetic research [16].
