People who eventually develop type 2 diabetes first pass through a stage of impaired glucose tolerance. At this point, they do not yet have diabetes, but are very likely to develop it. Research suggests that making dietary changes, starting an exercise program, and losing weight can help people with impaired glucose tolerance avoid developing diabetes. In addition, one study has suggested that taking the diabetes drug metformin (Glucophage) can help such people ward off diabetes. Now, research published in the June 15, 2002 issue of The Lancet suggests that the diabetes drug acarbose (Precose) may also help prevent the development of diabetes in people with impaired glucose tolerance.

About the study

This study was funded by Bayer AG, the company that manufactures acarbose. However, the study authors state that Bayer had no role in the study design, data analysis and interpretation, or writing of the report.

Between December 1995 and July 1998, researchers from the STOP-NIDDM Trial Research Group enrolled 1429 men and women between the ages of 40 and 70 with impaired glucose tolerance and a body mass index (BMI) of 25 to 40, which is considered overweight. Based on their glucose tolerance and body size, these participants would be expected to develop diabetes. Participants were from Canada, Germany, Austria, Norway, Denmark, Sweden, Finland, Israel, and Spain.

Participants were randomly assigned to take either 100 mg of acarbose or placebo (inactive pill) three times daily. All participants were given instructions on a weight-reduction or weight-maintenance program and encouraged to exercise regularly. They also had yearly appointments with a dietitian where they reported their dietary intakes and physical activity from the previous three days.

In August 2001, after an average of 3 years of follow-up, the researchers compared the number of people who developed diabetes in both the acarbose and the placebo groups.

The findings

People taking acarbose were 25% less likely to develop diabetes than their counterparts taking placebo. These numbers held true even after adjusting for age, sex, and BMI. Acarbose also helped people revert from impaired glucose tolerance to normal glucose tolerance.

Side effects more common in the acarbose group than the placebo group included stomach upset, excess gas, and diarrhea. Of note is that 19% of participants in the acarbose group dropped out of the study due to these unwanted side effects, compared with only 5% in the placebo group.

Although these results are interesting, there are limitations to this study.

Participants reported their dietary and exercise habits only once per year, and even this small amount of information was not included in the analysis. Therefore, we don’t know what role diet and exercise (two factors known to reduce the risk of diabetes) played in these results. In addition, 30% of people in the acarbose group dropped out of the study compared with only 18% in the placebo group. Although these people were included in the analysis, there is no way to know how they would have responded to the drug if they had remained in the study.

How does this affect you?

Should you take acarbose to prevent type 2 diabetes if you have impaired glucose tolerance? This study suggests that acarbose may help you ward off diabetes. However, diet and exercise have been shown to reduce the risk of developing diabetes by 58%, which is greater than the 25% risk reduction attributed to acarbose in this study. In a head-to-head comparison of diet and exercise versus the diabetes drug metformin, diet and exercise changes reduced the risk of diabetes by 39% more than metformin did. More research is needed to directly compare the effectiveness of acarbose with diet and exercise for reducing the risk of type 2 diabetes.

If you have impaired glucose tolerance, talk to your health care provider about medication and/or a modified diet and exercise plan to reduce your risk of developing type 2 diabetes. Together, you can make an informed decision about which options are appropriate for you.