High prevalence of retinopathy in young-onset type 2 diabetes and possible sex differences: insights from Norwegian general practice

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 A1c (HbA1c) 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, HbA1c increased faster in YOD, and at the time of diagnosis HbA1c 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 HbA1c), 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 HbA1c and longer T2D duration, but after accounting for these factors it remained higher in men with YOD. Data may be obtained from a third party and are not publicly available. The data underlying this article cannot be shared publicly due to the privacy of individuals who participated in the study. The data will be shared on reasonable request to the corresponding author if approved by the ethics committee.