Context: Microvascular processes have been hypothesized to play a role in the pathogenesis of type 2 diabetes mellitus, but prospective clinical data regarding this hypothesis are unavailable.
Objective: To examine the relation of retinal arteriolar narrowing, a marker of microvascular damage from aging, hypertension, and inflammation, to incident diabetes in healthy middle-aged persons.
Design, setting, and participants: The Atherosclerosis Risk in Communities Study, an ongoing population-based, prospective cohort study in 4 US communities that began in 1987-1989. Included in this analysis were 7993 persons aged 49 to 73 years without diabetes, of whom retinal photographs were taken during the third examination (1993-1995).
Main outcome measures: Incident diabetes (defined as fasting glucose levels of > or =126 mg/dL [7.0 mmol/L], casual levels of > or =200 mg/dL [11.1 mmol/L], diabetic medications use, or physician diagnosis of diabetes at the fourth examination) by quartile of retinal arteriole-to-venule ratio (AVR).
Results: After a median follow-up of 3.5 years, 291 persons (3.6%) had incident diabetes. The incidence of diabetes was higher in persons with lower AVR at baseline (2.4%, 3.1%, 4.0%, and 5.2%, from highest to lowest AVR quartile; P for trend < .001). After controlling for fasting glucose and insulin levels, family history of diabetes, adiposity, physical activity, blood pressure, and other factors, persons in the lowest quartile of AVR were 71% more likely to develop diabetes than those in the highest quartile (odds ratio [OR], 1.71; 95% confidence interval [CI], 1.13-2.57; P for trend =.002). This association persisted with different diagnostic criteria (OR, 1.92; 95% CI, 1.10-3.36; P for trend =.01, using a fasting glucose level of > or =141 mg/dL [7.8 mmol/L] as a cutoff), and was seen even in people at lower risk of diabetes, including those without a family history of diabetes, without impaired fasting glucose, and with lower measures of adiposity.
Conclusions: Retinal arteriolar narrowing is independently associated with risk of diabetes, supporting a microvascular role in the development of clinical diabetes.