A Decade Later, Lifestyle Changes or Medication Still Lower Type 2 Diabetes Risk
Study reports on persistence of benefits seen in the Diabetes Prevention Program
After following participants in the Diabetes Prevention Program Outcomes Study for 10 years, researchers at the University of Miami Miller School of Medicine and at 26 other medical centers in the United States conclude that intensive lifestyle changes aimed at modest weight loss reduced the rate of developing type 2 diabetes by 34 percent compared with placebo in people at high risk for the disease. Results of the study, which examines the persistence of the interventions first tested in the Diabetes Prevention Program, appear online in The Lancet on October 29.
Participants randomly assigned to make lifestyle changes also had more favorable cardiovascular risk factors, including lower blood pressure and triglyceride levels, despite taking fewer drugs to control their heart disease risk. Treatment with the oral diabetes drug metformin reduced the rate of developing diabetes by 18 percent after 10 years compared with placebo.
“At the Miller School’s Diabetes Research Institute we enrolled 150 patients in the initial study, and 130 continued in the ten year follow-up arm,” said Ronald Goldberg, M.D., professor of medicine and principal investigator of the study. “When you break down the findings they are dramatic. In ten years, participants in the lifestyle group, who made exercise and diet changes, delayed type 2 diabetes by about four years compared with placebo, while those in the metformin group delayed it by two years. When you consider the devastating medical complications that go along with type 2 diabetes, these are very significant findings.”
The benefits of intensive lifestyle changes were especially pronounced among the elderly. People age 60 and older lowered their rate of developing type 2 diabetes in the next 10 years by about half.
“The spiraling epidemics of obesity and type 2 diabetes in this country and worldwide show no signs of abating,” said Griffin P. Rodgers, M.D., director of the National Institute of Diabetes and Digestive and Kidney Diseases, part of the National Institutes of Health. “In the United States, about 11 percent of adults — 24 million people — have diabetes, and up to 95 percent of them have type 2 diabetes. An additional 57 million overweight adults have glucose levels that are higher than normal but not yet in the diabetic range. This condition substantially raises the risk of a heart attack or stroke and of developing type 2 diabetes in the next 10 years. Many could delay diabetes for years and possibly prevent the disease altogether if they lost a modest amount of weight through diet and increased physical activity.”
The Diabetes Prevention Program Outcomes Study (DPPOS) is a continuation of the Diabetes Prevention Program (DPP), a large, randomized trial in 3,234 overweight or obese adults with already elevated blood glucose levels. Researchers announced the initial findings of the DPP in 2001, a year earlier than scheduled, because results were so clear: After three years, intensive lifestyle changes reduced the development of type 2 diabetes by 58 percent compared with placebo. Metformin (850 milligrams twice a day) reduced it by 31 percent compared with placebo.
“Striking as the findings were, we could not say how long the benefit would endure, since the results were based on just three years of data,” said Goldberg. “This is why it was so important to continue a much longer period of follow-up, and we were fortunate that the NIH agreed and funded the continuation of the study.”
After a “bridge” period from January to July 2002, when all participants learned the results and were offered a 16-session program explaining how to make intensive lifestyle changes, the Diabetes Prevention Program Outcomes Study began, with 88 percent of volunteers from the original study taking part.
Intensive lifestyle changes consisted of lowering fat and calories in the diet and increasing regular physical activity to 150 minutes per week. Participants received training in diet, exercise (most chose walking), and behavior modification skills. In the first year of the DPP, this group lost 15 pounds on average but regained all but about five pounds over 10 years. The metformin group has maintained a loss of about five pounds, and the placebo group lost less than two pounds over the decade.
About five to six percent of those in the lifestyle intervention group developed type 2 diabetes annually, an incidence rate that remained steady throughout the DPPOS. When the DPP ended in 2001, the metformin and placebo groups were developing diabetes at the rate of eight and 11 percent a year, respectively. In 10 years, however, the yearly diabetes incidence rates for the drug and placebo groups had also fallen to about five to six percent, and the lifestyle intervention group’s rate remained at this lower level. The researchers are looking at a number of explanations for the convergence of diabetes incidence rates for the three groups. One may be that lifestyle changes adopted by the drug and placebo groups after the DPP ended may have lowered their rate of type 2 diabetes over time.
At enrollment in the DPP, participants ranged from age 25 to 85 years, with an average age of 51. They had an average body mass index (BMI) of 34, which is in the obese range. Forty-five percent of participants were from minority groups disproportionately affected by type 2 diabetes: African Americans, Hispanic/Latino Americans, American Indians, and Asian Americans and Pacific Islanders. The trial also recruited other groups at higher risk for type 2 diabetes, including people age 60 and older, women with a history of gestational diabetes, and people with a first-degree relative with type 2 diabetes.
Other studies have shown that diet and exercise delay type 2 diabetes in at-risk people. However, the DPP is the first major trial to show that lifestyle changes can effectively delay diabetes in a diverse population of overweight American adults at high risk of diabetes.