Lasting Effects of Lifestyle Change

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The long-term effect of lifestyle interventions to prevent diabetes in the China Do Qing Prevention Study: a 20-year follow-up study, by Guangwei Li and colleagues. Lancet 371:1783-1789, 2008

What is the problem and what is known about it so far?

Intensive lifestyle-change programs can prevent type 2 diabetes in people with impaired glucose tolerance (blood glucose levels higher than normal but not high enough to be diagnosed as diabetes). But no one knows how long the benefits of such programs last after the program is finished or whether such programs also reduce the risk of heart and blood vessel disease.

Why did researchers do this particular study?

The researchers wanted to find out whether an intensive group lifestyle-change program had a long-term effect on the risk of developing diabetes, diabetes-related complications, and death.

Who was studied?

This 2006 study included 568 adults with impaired glucose tolerance who had participated in a 6-year lifestyle-change study between 1986 and 1992 in China. The original study compared three lifestyle-change groups (featuring diet, exercise, or both) with a control group that did not have lifestyle-change measures.

How was the study done?

Researchers followed up with participants of the earlier study to find out how many of them had developed diabetes or heart disease and how many had died from heart disease or from any cause.

What did the researchers find?

Compared to those who had no lifestyle change measures, participants from the combined lifestyle-change portions of the original study were far less likely to develop diabetes over the next 20 years. After 20 years, 80% of the lifestyle-change participants had developed diabetes, compared to 93% of the participants who did not have lifestyle-change measures. Lifestyle-change participants who developed diabetes did so more than 3 years later than those who did not have lifestyle interventions. The study detected only small differences between the two groups in terms of heart disease events, heart disease deaths, or deaths from any cause.

What were the limitations of the study?

The design of the study prevented researchers from fully detecting possible differences among heart disease rates and death rates between the two groups. The finding that there were no major differences in these areas may therefore be incorrect. Also, because the participants were not re-tested periodically between the end of the original study and the 20-year mark, the rate of diabetes development after the original study ended could have been underestimated. Furthermore, researchers could not learn the specific reasons why the earlier lifestyle-change programs might have improved the rate of diabetes development.

What are the implications of the study?

Group lifestyle-change programs of several years in length may prevent or delay diabetes for many more years after the programs end. However, it remains unclear whether such programs also prevent heart disease and death.

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