Multifactorial lifestyle interventions in the primary and secondary prevention of cardiovascular disease and type 2 diabetes mellitus--a systematic review of randomized controlled trials.

This systematic review aims to summarize the available randomized trials of multifactorial lifestyle interventions in the primary and secondary prevention of coronary heart disease and type 2 diabetes mellitus. Randomized trials investigating the effects of lifestyle interventions including the elements of diet, physical activity, and stress management in people at increased risk for or with manifest coronary heart disease or type 2 diabetes mellitus were searched for in five electronic database and by citation tracking. Quality was assessed using the Cochrane Collaboration's risk of bias tool. Exploratory effect size calculations were performed for a variety of laboratory and clinical outcome measures. Twenty-five trials including a total of 7,703 participants met the inclusion criteria. Fifteen trials were in patients with coronary heart disease, seven in patients with type 2 diabetes mellitus, and three on primary prevention. The interventions varied greatly regarding concept, intensity, and providers. Compared to participants in "usual care" control groups, there were no consistent effects on lipid levels and blood pressure and small effects on body mass index and glycated hemoglobin (HbA1c). Composite cardiac event rates were significantly less in the intervention groups of the few trials reporting these outcomes. Mortality was also lower in the intervention groups, but the difference was not statistically significant, and confidence intervals were wide. The evidence base for multifactorial lifestyle interventions is weak. Effects on surrogate measures seem minor, but there may be clinically relevant effects on major clinical endpoints.