BACKGROUND: Diabetic retinopathy (DR), including diabetic macular edema (DME), is a microvascular complication of diabetes that may lead to clinically significant visual impairment, and is a leading cause of blindness in adults.
OBJECTIVES: To estimate the incidence rate of DR and DME in a cohort of newly diagnosed diabetic patients by diabetes subtype (type I and type II) in a UK population.
METHODS: We conducted a cohort study using The Health Improvement Network (THIN) database in the UK. A cohort of subjects with a first-ever diagnosis code for diabetes mellitus (DM) between January 1st 2000 and December 31st 2007 was followed from the date of first DM diagnosis (start date) to the diagnosis of DR (stop date), age 85 years, death, or 31 December 2007, whichever occurred first. Patients were also followed from start date to DME diagnosis. Age-standardized incidence rates (SIRs) were estimated through the direct method of standardization using a standard European population. Standardized rate ratios (SRR) were calculated to compare the SIR of DR and DME between type I and II.
RESULTS: The study cohort consisted of 64,983 newly diagnosed DM patients. Among 1,757 patients with type I diabetes, the SIR of DR was 29.39/1,000 person-years and the SIR of DMO was 7.13/1,000 person-years. Among 63,226 patients with type II diabetes, the SIR of DR was 21.94/ 1,000 person-years and the SIR of DMO was 5.12/1,000 person-years. The SRR for type I compared to type II diabetes was 1.34 (95%CI¼ 1.26–1.42) for DR and 1.39 (95%CI¼ 1.23–1.58) for DME.
CONCLUSIONS: The age-standardized incidence rates of DR and DME were higher in patients with type I compared to patients with type II diabetes in UK primary care.
