Diabetes incidence remains low after 10 years of lifestyle intervention in DPP trial

The prevention or delay of diabetes achieved with lifestyle intervention and metformin in the Diabetes Prevention Program trial persisted after 10 years, according to data published in The Lancet today.

The DPP Research Group conducted the DPP Outcomes Study (DPPOS) at an additional 5.7 years for 2,766 (88%) of the patients enrolled in the original trial. Nine hundred ten participants were from the lifestyle arm, 924 were from the metformin arm, and 932 were from the placebo groups.

At the start of the DPPOS, researchers informed participants of the main DPP results and unmasked treatment to those who had been assigned to metformin and placebo, which was stopped. They offered group-implemented lifestyle intervention all three groups. The metformin group continued to receive 850 mg metformin twice daily as tolerated.

In the original trial, diabetes incidence rates were 4.8 cases per 100 person-years in the lifestyle intervention group, 7.8 in the metformin group and 11.0 in the placebo group. In DPPOS, diabetes incidence rates for those assigned metformin and placebo in DPP dropped to rates similar to the intervention group: 5.9 cases per 100 person-years for those in the lifestyle intervention group vs. 4.9 for the metformin group and 5.6 for the placebo group.

The researchers noted that the lifestyle intervention had the greatest effect on participants from DPP who were aged 60 to 85 years when randomly assigned to metformin, which had no effect.

In the 10 years since patients were randomly assigned to a treatment arm, diabetes incidence has reduced by 34% in the lifestyle intervention group and by 18% in the metformin group compared with placebo.

Anoop Misra, MD, of the department of diabetes and metabolic diseases at Fortis Hospitals in New Delhi, India, wrote in an accompanying editorial that, while DPPOS answers some questions, it leaves others unanswered.

“Even if diabetes is suppressed or delayed (two years by metformin compared with placebo), is it cost-effective to take this drug over a decade to delay diabetes for two years?” Misra wrote. “… Whether prevention of diabetes or maintaining lower levels of glycemia in individuals with prediabetes would lead to any beneficial effect on cardiovascular endpoints or mortality remains to be resolved.”

Diabetes Prevention Program Research Group. Lancet. 2009;doi:10.1016/S0140-6736(09)61457-4.