Effect of tight blood glucose control versus conventional control in patients with type 2 diabetes mellitus: a systematic review with meta-analysis of randomized controlled trials.

Tight control of blood glucose reduces cardiovascular events and total mortality is conflicting. To summarize clinical effects of tight versus conventional glucose control in patients with type 2 diabetes. We systematically searched MEDLINE, EMBASE, Cochrane Library, and ISI Web of Knowledge with no limits of language and time. Further trials were searched from the reference lists of identified studies. We included randomized controlled comparing different levels of blood glucose control intensity in type 2 diabetic patients. Two independent reviewers extracted data of eligible studies using standard case report forms. We investigated total mortality, cardiovascular and microvascular events, and hypoglycemia in patients with type 2 diabetes. We used random-effects models to obtain relative risks (RR) with 95% confidence intervals (CI). We included 6 trials involving 27,654 patients. There was no significant effect of tight blood glucose control on all-cause mortality (RR 1.03; 95% CI 0.90-1.17) or cardiovascular mortality (RR 1.04; 95% CI 0.83-1.29). Tight glucose control reduced the risk for nonfatal MI (RR 0.85; 95% CI 0.76-0.95), although had no effect on the incidence of nonfatal stroke (RR 1.02; 95% CI 0.88-1.17). For microvascular events, tight glucose control reduced the risk progression of retinopathy (RR 0.80; 95% CI 0.71-0.91), incidence of peripheral neuropathy (RR 0.94; 95% CI 0.89-0.99), and progression of nephropathy (RR 0.55; 95% CI 0.37-0.80), but had not significant effect on the incidence of nephropathy (RR 0.69; 95% CI 0.42-1.14). The risk of severe hypoglycemia increased with tight glucose control (RR 2.39; 95% CI 1.79-3.18). Tight blood glucose control reduces the risk for some macrovascular and microvascular events, without effect on all-cause mortality and cardiovascular mortality. Tight glucose control increases the risk of severe hypoglycemia.