Objective: To establish the prevalence of known and undiagnosed diabetes mellitus and impaired glucose tolerance in a representative Norwegian adult population according to the 1980 World Health Organization Expert Committee diagnostic criteria.
Design: Screening survey applying questionnaire and non-fasting blood glucose followed by a fasting and an oral glucose tolerance test.
Setting: The county of Nord-Trøndelag, Norway, 1984-86.
Subjects: All inhabitants aged > or = 20 years (85,100); 90.3% participated. For previously unknown diabetes: all inhabitants > or = 40 years (53,001)--participation rate 84.7%.
Main outcome measure: Prevalence.
Results: The prevalence of previously known diabetes was 2.6% in men and 3.2% in women. Total diabetes prevalence > or = 40 years was 4.8% in men and 5.6% in women. The prevalence increased continuously with age until 90 years. One patient in five was previously undiagnosed. Impaired glucose tolerance in those with an abnormal non-fasting value was rare; only 0.9% in men and 0.2% in women. The prevalence of known diabetes was three times higher than 20-30 years ago and four times higher than 50 years ago. Except for known diabetes in the very old the prevalence corresponded well with recent Nordic studies.
Implications: The present diabetes prevalence was so high that interested general practitioners will get sufficient experience in follow-up of diabetic patients to facilitate a good quality of the care.