Cohort profile: Outcomes & Multi-morbidity In Type 2 diabetes (OMIT) – a national registry-based observational cohort with focus on care and treatment of key high-risk groups in Norway

PURPOSE: The ‘Outcomes & Multi-morbidity in Type 2 Diabetes’ (OMIT) is an observational registry-based cohort of Norwegian patients with type 2 diabetes (T2D) established to study high-risk groups often omitted from randomised clinical trials. PARTICIPANTS: The OMIT cohort includes 57 572 patients with T2D identified via linkage of Norwegian Diabetes Register for Adults and the Rogaland-Oslo-Salten-Akershus-Hordaland study, both offering data on clinical patient characteristics and drug prescriptions. Subsequently these data are further linked to the Norwegian Prescription Database for dispensed medications, the Norwegian Population Register for data on death and migration, Statistics Norway for data on socioeconomic factors and ethnicity and the Norwegian Directorate of Health for data on the general practices and clinical procedures involved in the care of cohort patients. OMIT offers large samples for key high-risk patient groups: (1) young-onset diabetes (T2D at age <40 years) (n=6510), (2) elderly (age >75 years) (n=15 540), (3) non-Western ethnic minorities (n=9000) and (4) low socioeconomic status (n=20 500). FINDINGS TO DATE: On average, patient age and diabetes duration is 67.4±13.2 and 12.3±8.3 years, respectively, and mean HbA(1c) for the whole cohort through the study period is 7.6%±1.5% (59.4±16.3 mmol/mol), mean body mass index (BMI) and blood pressure is 30.2±5.9 kg/m(2) and 135±16.1/78±9.8 mm Hg, respectively. Prevalence of retinopathy, coronary heart disease and stroke is 10.1%, 21% and 6.7%, respectively. FUTURE PLANS: The OMIT cohort features 5784 subjects with T2D in 2006, a number that has grown to 57 527 in 2019 and is expected to grow further via repeated linkages performed every third to fifth year. At the next wave of data collection, additional linkages to Norwegian Patient Registry and Norwegian Cause of Death Registry for data on registered diagnoses and causes of death, respectively, will be performed.