World Diabetes Day 2009

One of the recurring themes of BeyondApples.Org is that preventive health guidelines are and should be based on solid evidence. Most people in the general public appreciate that new drugs are rigorously tested in clinical trials — highly controlled experiments in which some people are given the new drug and others an old drug or placebo in order to measure its true effects. But many do not realize that similarly designed experiments are done to test for non-pharmacologic interventions, such as advice to quit smoking or lose weight. Thus when doctors tell us to stop smoking or exercise, it isn’t just lip service. When done in an evidence-based way, their recommendations are based on scientific data that shows that for people like us this advice has a real health benefit. In this blog entry, I discuss a groundbreaking study that shows that through intensive lifestyle interventions diabetes can be prevented. This topic is timely because today, November 14th 2009, is World Diabetes Day (www.worlddiabetesday.org).

Diabetes is a terrible disease. It affects 8 percent of the U.S. population and is a leading cause of end-stage kidney disease, blindness, and heart attacks. Overall diabetes is the fifth leading cause of death worldwide. Although effective treatments exist, like most diseases it is better not to get it in the first place. Controlling diabetes usually require lifelong medications and often daily insulin injections, and even those with well-controlled disease have frequent appointments with an array of specialists. We have known for years what the major risk factors for diabetes are*: family history, overweight (body mass index or BMI > 25 kg/m2), abdominal obesity (waist circumference > 35 inches in women, > 40 inches in men), sedentary lifestyle (low levels of physical activity), and impaired glucose tolerance (sugar levels that are abnormally high but not enough to diagnose diabetes). Given these risk factors, the big question on many people’s minds is can diabetes be prevented?

To evaluate this question, researchers in the late 1990s conducted a now landmark clinical trial called the Diabetes Prevention Program or DPP. In this study, over 3200 people at high risk for diabetes were randomly assigned to one of three groups — intensive lifestyle modification, daily oral medication, or placebo — and then followed for an average of three years. People in the lifestyle modification group were enrolled in a wellness program with the goal of achieving and maintaining a 7 percent weight loss through a low calorie, low fat diet and moderate intensity exercise (at least 150 minutes a week of brisk walking). Those in the medication group were given metformin, a medicine that is often used to treat diabetes. And those in the placebo group were given a placebo or dummy pill.

The results were impressive. Over the course of the study, about one-third of the people in the placebo group developed diabetes. In comparison, those taking metformin had a 31 percent lower risk of developing diabetes. Even more remarkable was that those in the lifestyle modification group were 58 percent less likely to develop diabetes than placebo. Weight loss was the most important predictor of risk of diabetes — for every kilogram (2.2 lbs) of weight loss risk of diabetes dropped by 16 percent. The study, which was published in the New England Journal of Medicine in 2002, showed that diabetes is preventable. For every 7 people that participate in similar lifestyle-intervention program over three years, one case of diabetes would be prevented (number needed to treat or NNT=6.9). Through an intense dieting and exercise program, it is possible to keep at-risk people from developing diabetes. 

When the study came out many experts wondered how long the benefits would last. Are we simply delaying the onset of diabetes or are we actually preventing it? Just this past month a follow up study was published in Lancet by the DPP group that helps answer that question. After 3 years in the lifestyle, metformin or placebo group all study participants were enrolled in a less-intense lifestyle counseling program for an average of 7 years. (Those in the metformin group received both medication and counseling.) They found that over the 7 years of follow up the incidence of diabetes in the three groups was the same — not too surprising given that all the participants received the same treatment. However, what was remarkable was that the differences in rates of diabetes from the first 3 years of the study persisted over the entire 10 years. Overall the rate of diabetes was 18 percent lower in the metformin group and 34 percent lower in the intensive lifestyle group. Thus the study concluded that the “prevention or delay of diabetes with lifestyle intervention or metformin can persist for at least 10 years.”

This study provided many new insights into diabetes prevention. However, science is a iterative, continuous process; like all studies with these results came new questions:

1. The lifestyle intervention in this study was intensive. Each patient in the lifestyle group participated in a 16-lesson curriculum covering diet, exercise, and behavior modfication taught by case managers on a one-to-one basis over 24 weeks. After this patients received individual sessions (usually monthly) and group sessions designed to reinforce the behavioral changes. This begs the question: is the intensity of this intervention realistic for most primary care practices? If not, can less intense interventions have similar impact?

2. The participants were at high risk for diabetes. They not only were overweight but already had signs of impaired glucose tolerance (called pre-diabetes). In fact, the study found that one-third of those with the placebo group developed diabetes over three years (10 percent risk per year). Do the results of this study apply to people at lower risk (e.g., overweight with normal blood sugars, family history of diabetes)?

3. This study showed conclusively that diabetes can be prevented. But in the end, the goal of preventive health care is to improve health, not necessarily to prevent diagnoses. So did the participants in the lifestyle modification group have improved health outcomes (e.g., less heart attacks, lower mortality)?

Over the next several years researchers in the DPP group and elsewhere will no doubt use science to answer these and other critical questions regarding diabetes prevention. Still I think those of us outside the walls of research can take home some important messages: a) diabetes is preventable, b) diabetes can be prevented by eating healthy and exercising, and c) that these benefits are long-lasting.

As we observe World Diabetes Day (www.worlddiabetesday.org) let us bear in mind these critical observations. I can think of no better way to “celebrate” World Diabetes Day than to renew each of our committments to a healthful lifestyle — a lifestyle which amongst other things will help us steer clear of diabetes and other chronic diseases.

- Shantanu Nundy, M.D.

* There are two major types of diabetes — type 1 or insulin-dependent diabetes and type 2 or non-insulin-dependent diabetes. Type 2 diabetes is by far more common and is associated with weight gain. In the blog entry, we use the term diabetes loosely to refer to type 2 diabetes.

To learn more about diabetes visit NIH ”Diabetes Overview” at http://diabetes.niddk.nih.gov/dm/pubs/overview/.

The lifestyle intervention course offered to participants in the DPP trial are available online at: http://www.bsc.gwu.edu/dpp/manuals.htmlvdoc.

To access original NEJM DPP article: http://content.nejm.org/cgi/content/abstract/346/6/393.

To access DPP followup article in Lancet: http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(09)61457-4/abstract.

To access accompanying Lancet editorial on preventing diabetes: http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(09)61631-7/fulltext.