gms | German Medical Science

Background/research question: The increasing prevalence of type II diabetes mellitus (T2DM) raises the question as to whether lifestyle interventions (diet/exercise) can delay or prevent the manifestation of T2DM and reduce the risk of micro- and macrovascular complications and premature death in high-risk individuals. Our aim was to determine whether systematic reviews exist that are able to answer our research question and thus provide a basis for the production of evidence-based health information.

Methods: We systematically searched for systematic reviews of controlled trials (CTs) in PubMed, the Cochrane Library and DARE in June 2013. The DIMDI, NICE and AHRQ websites were handsearched. Systematic reviews were included if they met predefined inclusion criteria and achieved an Oxman & Gyuatt Index ≥5. Two researchers independently screened 710 titles/abstracts and the resulting 48 full-text articles.

Results: We identified 9 relevant systematic reviews, of which 4 had the required quality. They differed in terms of the populations, interventions and outcomes included, as well as the search date. The most appropriate review (Jones et al. 2011) on lifestyle interventions (diet/exercise) and diabetes incidence in people with pre-diabetes included 11 randomised CTs in a meta-analysis: The pooled hazard ratio versus controls was 0.51 (95% CI 0.43-0.62). Assuming an annual diabetes incidence of 11% (as in the DPP study) the calculated absolute risk of diabetes would be 5.61% (95% CI 4.73- 6.82). Two other reviews (Dunkley et al. 2012; Sumamo et al. 2011) reported diabetes-related complications and mortality in people with metabolic syndrome on the basis of 2 and 4 randomised CTs, respectively. No significant differences were found between lifestyle intervention and control groups. The fourth review (LeBlanc et al. 2011) focused on weight loss and long-term health outcomes, but judged the available data to be insufficient.

Conclusions: Lifestyle interventions can prevent or delay the diagnosis of T2DM in high-risk individuals. The findings translate into an estimated effect of about 5 out of 100 individuals by reducing an assumed annual diabetes progression rate of 11 out of 100 to about 6 out of 100 individuals. The systematic procedure to find the best available external evidence resulted in a suitable basis for the production of evidence-based health information on diabetes prevention.