Concordance of retinopathy and nephropathy over time in Type 1 diabetes: an analysis of data from the Diabetes Control and Complications Trial

AimsLittle is known about the dynamic relationship over time between diabetic retinopathy and nephropathy. Thus, we sought to evaluate the concordance over time of retinopathy and nephropathy in patients with Type1 diabetes during the Diabetes Control and Complications Trial. MethodsThis analysis was conducted in patients with Type1 diabetes participating in the Diabetes Control and Complications Trial. Only participants with urinary albumin excretion rate <40mg/24h were included in the analysis (n=1365). We evaluated the relationship between the progression of retinopathy and the development of nephropathy over a mean 6.5years of follow-up. Progression of retinopathy was defined by 3-step change in Early Treatment Diabetic Retinopathy Study score on consecutive annual evaluations. Development of nephropathy was defined as incidence of urinary albumin excretion rate 40mg/24h on annual evaluation. ResultsOver a mean 6.5years of follow-up, the incidence of progression of retinopathy was higher in those who developed nephropathy than in those who did not (36.2 vs. 13.4%; P<0.001). The development of nephropathy independently increased the risk for progression of retinopathy (hazard ratio1.62, 95%CI 1.23-2.13, P=0.001), after adjustment for age, gender, diabetes duration, treatment, HbA(1c), BMI, HDL cholesterol and blood pressure. Similarly, the incidence of nephropathy was higher in participants who had progression of retinopathy than in those who did not (40.7 vs. 15.7%; P<0.001). Furthermore, progression of retinopathy independently increased the risk for development of nephropathy (hazard ratio1.72, 95%CI 1.30-2.27, P<0.001). ConclusionsProgression of retinopathy and development of nephropathy each increase the risk for incidence of the other, independent of established risk factors for microvascular complications, supporting the notion of a shared aetiologic basis. What's new? Approximately one quarter of participants (23.6%) had discordant progression of diabetic retinal and renal disease during the Diabetes Control and Complications Trial. Importantly, progression of diabetic retinopathy significantly increased the risk for development of diabetic nephropathy independently of established risk factors for microvascular complications. Similarly, the development of diabetic nephropathy independently increased the risk for diabetic retinopathy progression. These data potentially support the notion of a shared aetiologic basis and suggest that, in practice, the detection of either diabetic retinopathy progression or diabetic nephropathy development may indicate a need for closer surveillance for the other complication.