Interventions to Prevent Progression to Type 2 Diabetes
Background: Persons with impaired glucose tolerance have a high risk of developing type 2 diabetes. Many lifestyle, herbal, and phar-macologic interventions have been studied to prevent or significantly delay this progression; however, the relative effectiveness of these interventions is unclear. The rapidly increas-ing incidence of diabetes makes gaining infor-mation about the most effective preventive strategies of critical importance. Gillies and colleagues conducted a meta-analysis to com-pare the effectiveness of pharmacologic and lifestyle interventions in preventing or delay-ing the development of type 2 diabetes.
The Study: To identify relevant studies, the authors used electronic databases, references of published studies and reviews, and expert recommendations. Inclusion was limited to good-quality randomized controlled trials that clearly defined patients with impaired glucose tolerance and included the develop-ment of diabetes as the primary outcome measure. Three reviewers had to approve each study for inclusion in the meta-analysis. From more than 11,000 identified articles, 17 trials with 8,084 total participants were included in the meta-analysis. Pharmacologic interventions were orlistat (Xenical), oral diabetes medication, and the jiangtang bushen herbal regimen. Lifestyle interven-tions comprised diet and/or exercise.
Results: All interventions were effective in preventing or delaying diabetes. When con-sidered separately, diet, exercise, and a com-bination each had a relative risk reduction of 49 percent. The pooled effect for all lifestyle interventions had a hazard ratio of 0.51; this was equivalent to a number needed to treat (NNT) of 6.4. Lifestyle interventions were more effective in participants with initially higher body mass indices. Oral diabetes med-ication and orlistat also were highly beneficial with pooled hazard ratios of 0.70 and 0.44, respectively. The herbal regimen had a hazard ratio of 0.32. The NNTs for diabetes medica-tion, orlistat, and the herbal regimen were 10.8, 5.4, and 4.0, respectively. Adverse events were mainly gastrointestinal upsets related to medications; the reported incidence of adverse events varied widely among trials.
Conclusion: The authors conclude that lifestyle and pharmacologic interventions equally reduce progression to type 2 diabetes in persons with impaired glucose tolerance. These interventions can halve the risk of diabetes in these patient. A clear understand-ing of potential adverse effects of long-term pharmacologic therapy is needed for an accu-rate risk-benefit assessment.
Source: Gillies CL, et al. Pharmacological and lifestyle interventions to prevent or delay type 2 diabetes in people with impaired glucose tolerance: systematic review and meta-analysis. BMJ February 10, 2007;334:299-302.
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