Clinical Question: Does intensive treatment of type 1 diabetes reduce the risk of cardiovascular events?

Setting: Outpatient (specialty)

Study Design: Randomized controlled trial (double-blinded)

Allocation: Uncertain

Synopsis: This study was a long-term follow-up of patients in the landmark Diabetes Control and Complications Trial (DCCT). Of 1,441 patients originally randomized to intensive or conventional treatment of type 1 diabetes between 1983 and 1989, 1,421 completed the study in 1993, and 1,182 were still available for follow-up in 2004. At the end of the initial 6.5-year study, patients in the intensive control group had a mean A1C of 7.4 percent compared with 9.1 percent in the usual treatment group.

Almost all patients opted for intensive treatment under the supervision of their local physician in 1993, and by 2004, the mean A1C was similar between groups (7.9 versus 7.8 percent). Groups were similar in 2004 regarding blood pressure; lipid control; and use of medications such as hormone therapy, aspirin, statins, angiotensin-converting enzyme inhibitors, and beta blockers. By 2004, the likelihood that a patient would experience a cardiovascular event (i.e., cardiovascular death, nonfatal or silent acute myocardial infarction, revascularization, confirmed angina, or nonfatal stroke) was lower in the intensive treatment group (0.38 versus 0.80 per 100 patient-years of follow-up;P = .008). Put another way, this means intensive therapy prevented one event for every 25 patients treated over 10 years. There was no difference in the likelihood of renal failure (1 percent in each group), and data regarding all-cause mortality were not reported. Given the relatively young average age of this group (45 years), it is not surprising that there was no difference reported regarding the latter outcomes.

Bottom Line: This extension of DCCT provides the first high-quality evidence that intensive treatment of type 1 diabetes reduces the risk of adverse cardiovascular outcomes. Although the relative risk reduction was greater than 50 percent, the absolute risk reduction was modest. Note that this effect has not been shown in patients with type 2 diabetes, although many patients and physicians believe otherwise, and data regarding all-cause mortality or adverse effects of intensive treatment (e.g., hypoglycemic episodes or traffic incidents) are not reported. (Level of Evidence: 1b)