Fifteen-year follow-up of the DPP (Diabetes Prevention Program) study has shown that lifestyle change and metformin are both effective in preventing type 2 diabetes in people at high risk of the condition.
In the original DPP study, conducted between 1996 and 2001, people who were overweight/obese and with elevated fasting and post-load blood glucose were randomised to receive metformin 850 mg twice daily, placebo or an intensive lifestyle intervention comprising regular individual and group sessions aiming to achieve ≥7% weight loss with a low-fat, low-calorie diet and 150 minutes of moderate exercise per week. After 3 years of follow-up, the incidence of diabetes per 100 person-years was 11.0, 7.8, and 4.8 in the placebo, metformin and lifestyle groups, respectively, with both interventions significantly better than placebo in preventing the condition, and with lifestyle significantly more effective than metformin.
At the conclusion of DPP, 2776 participants agreed to be followed in DPPOS (the DPP Outcomes Study), in which the metformin group continued to receive metformin (now open-label) and all participants received the lifestyle intervention for 1 year, along with quarterly group maintenance sessions. In addition, the original lifestyle group were offered supplementary group programmes and individual check-ups twice per year.
At the 15-year follow-up, compared with the placebo group, the incidence of diabetes was lower in both the lifestyle (hazard ratio [HR], 0.73; P<0.001) and the metformin groups (HR, 0.82; P=0.001). While there was still a difference in efficacy between lifestyle and metformin, this had reduced and was no longer significant (P=0.1). The cumulative incidence of diabetes was 55%, 56% and 62% in the lifestyle, metformin and placebo groups, respectively.
In terms of the microvascular complications of diabetes, there was no overall difference between the groups. However, an effect was observed in women, with the lifestyle group showing a lower prevalence compared with the placebo (relative risk [RR], 0.79; P=0.03) and metformin (RR, 0.78; P=0.02) groups. The authors are unable to explain this but note that a similar gender effect was observed for nephropathy in the Look AHEAD (Action for Health in Diabetes) study.
In their conclusion, the authors state: “The results of the DPPOS have shown very long-term effects of lifestyle intervention and metformin to reduce the incidence of diabetes in a population at very high risk. However, most participants in each treatment group developed diabetes 15 years after enrolment. Therefore, interventions with greater long-term efficacy for diabetes prevention are still needed.”
The study results can be read in full here.
