Objective: We conducted a systematic review of randomized controlled trials (RCTs) of intensive insulin therapy (IIT) in type 1 diabetes to determine the effect on macrovascular complications.
Research design and methods: MEDLINE (1966-1996), Citation Index, reference lists, and personal files were used to identify RCTs of > 2 years' duration comparing IIT to conventional therapy (CT) in type 1 diabetes. Two independent reviewers applied selection criteria and identified 11 studies; 5 were subsequently excluded because no data were available for macrovascular complications. Data were extracted on macrovascular disease and cardiovascular risk factors. Macrovascular disease was defined as angina, myocardial infarction, angioplasty, coronary artery bypass graft, stroke, claudication, or peripheral bypass. The first event of each type was counted.
Results: IIT decreased the number of macrovascular events (odds ratio [OR] 0.55, [95% CI 0.35-0.88], P = 0.015) but had no significant effect on the number of patients developing macrovascular disease (OR 0.72, [95% CI 0.44-1.17], P = 0.22) or on macrovascular mortality (OR 0.91, [95% CI 0.31-2.65], P = 0.93).
Conclusions: IIT decreases the extent of early macrovascular disease in young individuals with type 1 diabetes but has no effect on the number of patients affected or on macrovascular mortality. These data suggest that IIT may stabilize macrovascular disease or prevent progression in those at risk.