The recommendation attaches a relatively high value on the many beneficial effects of the diet used in the studies as well as exercise on other outcomes in addition to diabetes prevention, and the lack of significant adverse effects of these interventions, and on avoiding pharmacological treatment when an equally effective and safe lifestyle intervention is available.
The Diabetes Prevention Program Outcomes (DPPO) study «Aroda VR, Christophi CA, Edelstein SL et al. The e...»2 examined the effect of lifestyle intervention and metformin on preventing or delaying diabetes among women with and without gestational diabetes (GDM). A lifestyle-modification program (goals: at least a 7% weight loss and at least 150 minutes of physical activity per week) was compared with metformin (850 mg twice daily) and with placebo. The incidence of diabetes was 11.0, 7.8, and 4.8 cases per 100 person-years in the placebo, metformin, and lifestyle groups, respectively. The lifestyle intervention reduced the incidence by 58% (95% CI, 48 to 66%) and metformin by 31% (95% CI, 17 to 43%), as compared with placebo; the lifestyle intervention was significantly more effective than metformin. To prevent one case of diabetes during a period of three years, 6.9 persons would have to participate in the lifestyle-intervention program, and 13.9 would have to receive metformin. All 3 groups were offered group-implemented lifestyle intervention. Metformin treatment was continued in the original metformin group. During the 10-year follow-up, the original lifestyle group lost, then partly regained weight. The modest weight loss with metformin was maintained. Diabetes incidence rates in this follow-up study were similar between treatment groups: 5.9 per 100 person-years (5.1-6.8) for lifestyle, 4.9 (4.2-5.7) for metformin, and 5.6 (4.8-6.5) for placebo. Diabetes incidence in the 10 years since randomisation was reduced by 34% (24-42) in the lifestyle group and 18% (7-28) in the metformin group compared with placebo.
A study «...»6 assessed long-term persistence of intervention effects on diabetes incidence after 21 years, and heterogeneity of effects in subgroups defined by baseline diabetes risk factors. 3195 participants originally enrolled in the DPP were included. During follow-up, compared with placebo, diabetes incidence rate was reduced in the original intensive lifestyle intervention (ILS) group (HR 0.76, 95% CI 0.68 to 0.85, rate difference [RD] -1.59 cases per 100 person-years) and in the original metformin group (HR 0.83, 95% CI 0.74 to 0.93, RD -1.17, with corresponding increases in median diabetes-free survival of 3.5 years and 2.5 years, respectively. The diabetes cumulative incidence curves separated early, especially in the first 3 years, with lower incidence rates in the metformin and ILS groups than in the placebo group. The metformin and ILS curves progressively converged with longer follow-up. The overall treatment effects appeared to result from large early effects during the DPP. Absolute intervention effects, measured as RDs versus placebo, were greater with ILS in participants with higher values for baseline fasting glucose, HbA1c, and multivariable clinical and physiological risk indices, and with metformin in younger participants.
A Cochrane review «Metformin for prevention or delay of type 2 diabetes mellitus and its associated complications in persons at increased risk for the development of type 2 diabetes mellitus»1 «Madsen KS, Chi Y, Metzendorf MI et al. Metformin f...»1 included 20 studies with a total of 6774 subjects. The DPPO study contributed 48% of all participants. Comparing metformin with diet and exercise with or without placebo, incidence of type 2 diabetes (T2D) was significantly lower (RR 0.50, 95% CI 0.38 to 0.65; P < 0.001; 12 trials, n=3632). Comparing metformin with intensive diet and exercise, incidence of T2D was similar (RR 0.80, 95% CI 0.47 to 1.37; P = 0.42; 7 trials, n=2960), though there was a trend favouring metformin. In 3 RCTs comparing metformin plus intensive diet and exercise with identical intensive diet and exercise incidence of T2D was similar (RR 0.55, 95% CI 0.10 to 2.92; P = 0.49; n=332). There were no differences in all-cause or cardiovascular mortality, non-fatal myocardial infarction or stroke, probably the follow-up was too short. Serious adverse events were poorly reported.
In part of the Diabetes Prevention Program (DPP) «Ratner RE, Christophi CA, Metzger BE et al. Preven...»4 women with impaired glucose tolerance (350 with prior GDM and 1416 without GDM) were randomized to either standard lifestyle and placebo (n=122, placebo group) or standard lifestyle and metformn 850mg bid. (n=111, metformin group), or to an intensive lifestyle intervention (n=117, ILS group). Whereas entering the study with similar glucose levels, women with a history of GDM randomized to placebo had a crude incidence rate of diabetes 71% higher than that of women without such a history. Among women reporting a history of GDM, both intensive lifestyle and metformin therapy reduced the incidence of diabetes by approximately 50% compared with the placebo group.
In 15-year follow-up of DPP-study «Diabetes Prevention Program Research Group.. Long-...»3 the subgroups that benefited most were assessed. During the DPP adults at high risk were randomly assigned to masked placebo (n=1082) or metformin 850 mg twice daily (n=1073). Participants originally assigned to metformin continued to receive metformin unmasked. Metformin reduced the incidence (by hazard ratio [HR]) of diabetes compared to placebo by 17% or 36% based on glucose tolerance test or HbA1c levels, respectively. Metformin's effect was greater for women with a history of prior GDM (HR 0.59, rate differences -4.57 cases/100 person-years) compared with parous women without GDM (HR 0.94, rate difference -0.38 cases/100 person-years [interaction P = 0.03 for HR, P = 0.01 for rate difference]). Metformin also had greater effects at higher baseline fasting glucose levels.
A study «Pérez-Ferre N, Del Valle L, Torrejón MJ et al. Dia...»5 evaluating the efficacy of a lifestyle intervention for the prevention of glucose disorders (impaired fasting glucose, impaired glucose tolerance or T2D) included 260 women with prior GDM. Women were randomised to a Mediterranean lifestyle intervention group (an educational program on nutrition and a monitored physical activity program) and a control group with a conventional follow-up. Less women in the intervention group (42.8%) developed glucose disorders at the end of the 3-year follow-up compared with the control group (56.75%). Glucose disorders were reduced especially with a BMI of less than 27 kg/m² (OR 0.28, 95% CI 0.12 to 0.65) and low fat intake pattern (OR 0.30, 95% CI 0.13 to 0.70).