Clinical review 51: Implications of the Diabetes Control and Complications Trial

The next generation of artificial pancreas control algorithms

Creating a wearable artificial pancreas (AP) by closing the loop between a glucose sensor and an insulin infusion pump has the potential to significantly impact the complications associated with and improve the quality of life of diabetic individuals. Despite recent progress on glucose sensor and insulin infusion technologies, control algorithms built on the simple glucose value efferent and insulin dose afferent model are not efficient and reliable. Based on glucose regulatory mechanisms known to date, their impairment in the diabetic state, and fundamental principles of control theory, some corrections to the present course of research are proposed to facilitate the removal of this barrier. A greater emphasis on model predictive controllers or controllers that exploit a mathematical representation, or model, of the patient's own physiology is proposed. Whole-body physiologically based pharmacokinetics-pharmacodynamics-type models hold the best odds for enabling a successful closed-loop AP. However, two major improvements to the diabetes modeling state of the art are required to make them practical for daily care: integrating hypothalamus-pituitary-adrenal axis and gastrointestinal tract submodels. Although there are simple representations of these in current existence, large concerted efforts between experimentalists and modelers will be required to enhance their accuracy. Finally, changes in hardware that complements controller performance are suggested. For instance, the development of dual control inputs of insulin and glucagon could relax tolerances on controller accuracy.

Lifetime costs of complications resulting from type 2 diabetes in the U.S

OBJECTIVE

To model the lifetime costs associated with complications of type 2 diabetes.

RESEARCH DESIGN AND METHODS

A cohort of 10,000 patients with diabetes was simulated using a model based on existing epidemiological studies. Complication rates were estimated for various stages of macrovascular disease, nephropathy, retinopathy, neuropathy, and hypoglycemia. At the beginning of the simulation, patients were assumed to have been treated for 5 years and have a mean HbA1c of 8.4. From the U.K. Prospective Diabetes Study, it was estimated that on current therapies, the HbA1c would drift upward on average 0.15% per year. Direct medical costs of managing each complication were estimated (in 2000 U.S. dollars) from all-payor databases, surveys, and literature.

RESULTS

Macrovascular disease was estimated to be the largest cost component, accounting for 85% of cumulative costs of complications over the first 5 years. The costs of complications were estimated to be $47,240 per patient over 30 years, on average. The management of macrovascular disease is estimated to be the largest cost component, accounting for 52% of the costs; nephropathy accounts for 21%, neuropathy accounts for 17%, and retinopathy accounts for 10% of the costs of complications.

CONCLUSIONS

The complications of diabetes account for substantial costs, with management of macrovascular disease being the largest and earliest. If improving glycemic control prevents complications, it will reduce these costs.