Aims/hypothesis: This study aimed to examine recent time trends in the incidence and prevalence of type 2 diabetes in Norway.
Methods: In this Norwegian nationwide cohort study, we linked data from national registries with prospectively collected data on diabetes medication and diabetes diagnoses for all residents in Norway aged 30 to 89 years (>3.2 million people). We analysed trends in incidence and prevalence of type 2 diabetes from 2009 to 2014 by type of treatment, sex, age, education level and place of birth.
Results: During 15,463,691 person-years of follow-up from 2009 to 2014, we identified 75,496 individuals with new-onset type 2 diabetes. Of these, 36,334 (48%) were treated with blood-glucose-lowering drugs within 6 months of diagnosis. A low education level and being born in Asia, Africa or South America were significant risk factors for incident type 2 diabetes. While the prevalence of type 2 diabetes increased from 4.9% to 6.1% during the study period, the incidence decreased significantly from 609 cases per 100,000 person-years in 2009 to 398 cases per 100,000 in 2014, an annual reduction of 10.1% (95% CI -10.5, -9.6). A declining incidence was seen for both pharmacologically and non-pharmacologically treated type 2 diabetes, and in all subgroups defined by sex, age group, education level and place of birth.
Conclusions/interpretations: This nationwide study shows that, despite a decreasing incidence of type 2 diabetes in Norway, the prevalence continues to rise, probably due to diagnosis at a younger age and increased longevity.
Keywords: Incidence; Prevalence; Register-based study; Time trends; Type 2 diabetes.