Better glycaemic control and risk reduction of diabetic complications in Type 2 diabetes: comparison with the DCCT

Objective: To construct dose response curves relating the development of di abetic complications (retinopathy and microalbuminuria) to mean glycaemic e xposure in a cohort of Type 2 patients followed over a period of several ye ars. This allows a comparison with similar data on Type 1 subjects reported by the Diabetes Control and Complications Trial (DCCT) and provides a rati onal basis for deciding what levels of glycaemic control should be aimed fo r in advising individual patients and in setting guidelines for conducting health services. Research design and methods: This was an analysis of data prospectively collected in our computerized data base for Type 2 patients w ho attended and were followed up at the Complications Assessment Service of our Diabetes Center. The initial development of retinopathy and microalbum inuria was analyzed with respect to the mean HbA(1c) during the follow up p eriod. Statistical procedures identical to those employed in the DCCT were used to construct the dose response curve. Results: A smooth relationship b etween the development of retinopathy with increasing hyperglycaemia was fo und. For every 10% decrease in HbA(1c), there was a 24% (confidence interva l (CI): 16-32) reduction in relative risk, about 2/3 of that reported for i nsulin-dependent diabetes mellitus (IDDM) patients. The relationship betwee n microalbuminuria and HbA(1c) was more linear and less steep with a relati ve risk reduction of 9% (CI: - 2-19%) for any 10% fall in HbA(1c), about 1/ 3 of that reported for IDDM subjects. No threshold of HbA(1c) can be found for the relative risk of developing complications. However, more cases of c omplications are prevented by the same degree of improvement in glycaemic c ontrol at higher levels of HbA(1c). Conclusions: The development of diabeti c retinopathy in Type 2 subjects is also related to the magnitude of hyperg lycaemia although the degree of dependence is less than that in Type 1. Gly caemic control has less influence on microalbuminuria in Type 2. In terms o f relative risk, no threshold of 'safe HbA(1c)' can be found but in absolut e terms more cases of diabetic complications can be prevented by improving the glycaemic control of the very hyperglycaemic patients. (C) 1998 Elsevie r Science Ireland Ltd. All rights reserved.