Abstract
INTRODUCTION: People with young-onset type 2 diabetes (YOD), defined as diabetes diagnosis before age 40, have a high lifetime risk of vascular complications. We aimed to estimate the prevalence of YOD among adults with type 2 diabetes (T2D) in Norwegian general practice and explore associations between age at diabetes diagnosis and retinopathy overall and in men and women. RESEARCH DESIGN AND METHODS: We collected cross-sectional data from general practice electronic medical records of 10 241 adults with T2D in 2014, and repeated measurements of hemoglobin A(1c) (HbA(1c)) from 2012 to 2014. Using multivariate logistic regression, we assessed associations between YOD and later-onset T2D, sex and retinopathy. RESULTS: Of all individuals with T2D, 10% were diagnosed before 40 years of age in both sexes. Compared with later-onset T2D, HbA(1c) increased faster in YOD, and at the time of diagnosis HbA(1c) was higher in men, particularly in YOD. Retinopathy was found in 25% with YOD, twice as frequently as in later onset. After adjustments for confounders (age, country of origin, education, body mass index), OR of retinopathy was increased in both men with YOD (OR 2.6 (95% CI 2.0 to 3.5)) and women with YOD (OR 2.2 (1.5 to 3.0)). After further adjustments for potential mediators (diabetes duration and HbA(1c)), the higher OR persisted in men with YOD (OR 1.8 (1.3 to 2.4)) but was attenuated and no longer significant for women with YOD. CONCLUSIONS: Retinopathy prevalence was more than twice as high in YOD as in later-onset T2D. The increased likelihood of retinopathy in YOD was partly mediated by higher HbA(1c) and longer T2D duration, but after accounting for these factors it remained higher in men with YOD.