A systematic review of interventions for diabetic retinopathy, published in the American Journal of Ophthalmology, has found that intensive insulin pump therapy, compared to multiple daily injections, is more effective in preventing the occurrence and progression of diabetic retinopathy (DR). The results of the study, applicable to both adults and adolescents with Type-1 diabetes, showed that not all modes of intensive insulin therapy are equally effective. Previous studies assumed that intensive insulin therapy, whether delivered through continuous subcutaneous insulin infusion or through multiple daily injections, would have similar impact on micro-vascular outcomes. However, the current review and meta-analyses (American Journal of Ophthalmology, Nov 2015, http://dx.doi.org/10.1016/j.ajo.2015.07.024) suggests this may not be the case.
The review, conducted by Dr. Sohaib Kirk and colleagues at the Institute of Endocrinology and Diabetes, Westmead’s Children’s Hospital, Sydney, Australia, showed that in the largest cohort study included in the meta-analyses, there was a 55% risk reduction in the incidence of diabetic retinopathy for continuous subcutaneous insulin infusion, relative to multiple daily injections. Overall, the research identified 7,847 records, primarily via electronic searches, from which 24 studies involving 9,302 patients met the strict inclusion criteria. From analyses of the filtered available data, the authors found that incident diabetic retinopathy was reduced by intensive versus conventional insulin therapy (RR 0.43; 95% CI 0.23–0.83) and that in particular, insulin pumps versus multiple daily injections (RR 0.45; 95% CI 0.24–0.83) were significantly more effective. In 5 studies that included a total of 2,168 patients, intensive insulin therapy significantly reduced the risk of incident diabetic retinopathy relative to conventional insulin therapy (17.5% vs 29.8%; RR 0.43; 95% CI, 0.23–0.83; P = .01; I2 = 75%), while in a single study that directly compared continuous subcutaneous insulin infusion with multiple daily injection therapy, the continuous infusion provided greater protection against the development of the disease (9.1% vs 20.4%; RR 0.45; 95% CI, 0.24–0.83; P = .01).
In concluding their analyses the Australian-based researchers stated that, “there is strong evidence supporting intensive insulin therapy for prevention of DR in both young people and adults with type 1 diabetes, with some evidence for added protection with continuous subcutaneous insulin infusion over multiple daily injections. In addition, the authors of the study commented that “AIIRAs (angiotensin II receptor antagonists) and ACE (angiotensin-converting enzyme) inhibitors reduce the risk of DR incidence and progression, respectively, in normotensive, normoalbuminuric adults, but their effectiveness in other populations is yet to be reported.” Finally, the authors highlight that their current study is the first report on the benefit of intensive insulin treatment independent of the DCCR (Diabetes Control and Complications Trial), conducted over 20 years ago and before any of the newer insulin analogues or current delivery methods were available.