Effectiveness of interventions for reducing diabetes and cardiovascular disease risk in people with metabolic syndrome: systematic review and mixed treatment comparison meta-analysis

Aims: To review the evidence on interventions for reversing metabolic syndrome or preventing development of type 2 diabetes and cardiovascular disease in people with metabolic syndrome. Methods: A systematic review and Bayesian mixed treatment comparison meta-analysis was conducted. Relevant electronic bibliographic databases were searched up to January 2010. Included studies were randomized controlled trials with a follow-up of =24 weeks and outcomes comparing incidence of diabetes and/or cardiovascular disease, or reversal of metabolic syndrome. Results: A total of 16 studies met the inclusion criteria. Thirteen studies with outcome data for reversal of metabolic syndrome, involving 3907 participants, were included in the meta-analysis. Insufficient trials reported cardiovascular events/mortality, or incidence of type 2 diabetes, to conduct a meta-analysis for these outcomes. Interventions, alone or in combination, included lifestyle (diet and/or exercise) and pharmacological therapy. Using random-effect models, both lifestyle (odds ratio, OR 3.81; 95% confidence interval, CI 2.475.88) and pharmacological interventions (OR 1.59; 95% CI 1.042.45) were statistically superior compared with control for reversing metabolic syndrome. Using mixed treatment comparison methods, the probability that lifestyle interventions were the most clinically effective was 87%. Conclusions: Evidence suggests that both lifestyle and pharmacological interventions can reverse metabolic syndrome. However, there is a lack of data on whether these benefits are sustained and translate into longer term prevention of diabetes and/or cardiovascular disease.