OBJECTIVE—To determine the age- and sex-specific prevalence of impaired fasting glycemia, impaired glucose tolerance, screen-detected diabetes, and known diabetes in a Danish population aged 30–60 years and to examine the phenotype and the cardiovascular risk profile in individuals with impaired glucose regulation.

RESEARCH DESIGN AND METHODS—In the Inter99 study, 13,016 inhabitants living in Copenhagen County were invited. All participants underwent anthropometric measurements, blood samples, and a 75-g standardized oral glucose tolerance test.

RESULTS—The age-specific prevalences in men were as follows: impaired fasting glycemia: 1.4–16.3%; impaired glucose tolerance: 6.9–17.8%; screen-detected diabetes: 0.7–9.7%; and known diabetes: 0–5.8%. The corresponding figures in women were 0–5.1, 10.5–17.3, 0.6–6.3, and 0.5–9%. The prevalence of impaired glucose regulation increased with age. Among individuals with diabetes, 65.6% were previously undiagnosed; this proportion was highest in the youngest age-group (82% among 45-year-old men vs. 63% among 60-year-old men, and 70% among 45-year-old women vs. 52% among 60-year-old women). Mean BMI, waist, HbA_1c, systolic blood pressure, diastolic blood pressure, and total cholesterol were significantly higher (P < 0.0001) in the individuals with impaired glucose regulation compared with individuals with normal glucose tolerance.

CONCLUSIONS—This study revealed that the prevalence of type 2 diabetes is high and that still two out of three individuals are undiagnosed, indicating a need for more attention to the disease in society.