Lifestyle Changes Delays Diabetes for Decades

In patients with impaired glucose tolerance, eating healthier and getting more exercise reduced the risk of diabetes for up to 20 years, researchers found. Over a 20-year period, patients who received a six-year lifestyle intervention had a 43% lower rate of diabetes than controls (hazard rate ratio 0.57, 95% CI 0.41 to 0.81), Guangwei Li, M.D., of China-Japan Friendship Hospital here, and colleagues reported in the May 24 issue of The Lancet.

After 20 years, 80% of the patients in the intervention group had diabetes compared with 93% in the control group.  Those in the intervention group delayed the onset of diabetes by an average of 3.6 years, the researchers said.  There was no significant difference, however, in the rates of cardiovascular disease or death between the groups.

"Widespread adoption of such interventions offers the prospect that projected increases in type 2 diabetes could be attenuated," they said.

"Since around three million excess deaths a year are attributable to diabetes worldwide," they concluded, "lifestyle interventions seem to be a justifiable public health action both in developed and developing nations." 

Although it’s well known that interventions aimed at modifying lifestyle can reduce the risk of diabetes, it’s unclear how long the benefits last after stopping the interventions. It is also not known to what extent these interventions reduce the risk of cardiovascular events, the researchers said.

In 1986, 576 Chinese adults who had impaired glucose tolerance were randomized to a control group (138) or one of three intervention groups (438) — diet, exercise, or diet and exercise — for six years as part of the China Da Qing Diabetes Prevention Study.

The diet intervention focused on increasing vegetable intake and reducing consumption of alcohol and sugar. The exercise intervention aimed to increase leisure time physical activity. All three intervention groups were pooled for the analysis because of concerns about statistical power.  At baseline, participants in the intervention group were about two years younger than the controls.

Between-group differences in blood pressure, total cholesterol, and changes in body weight were not significant at any time during the study.

During the intervention period, there was a 51% lower rate of diabetes in the intervention group than in the control group (hazard rate ratio 0.49, 95% CI 0.33 to 0.73).

In 2006, 14 years after the intervention had ended, the researchers followed up on all available participants for the China Da Qing Diabetes Prevention Outcomes Study.  During the entire study there were 145 strokes, 66 myocardial infarctions, and 142 deaths, of which 68 were attributed to cardiovascular disease.

The findings, the researchers said, are consistent with those of the Finnish Diabetes Prevention Study, in which the benefits of a lifestyle intervention persisted up to three-and-a-half years

Dr. Li and colleagues proposed three broad mechanisms for the persistent effect of the lifestyle interventions, including the possibility that participants permanently adopted the behavioral changes introduced by the interventions.  The interventions might also have changed the preventive care and health promotion efforts of the individual clinics in the study, they said.  And finally, the interventions might have led to some type of metabolic memory, they said. "Effects on insulin secretion or sensitivity that are well documented over the short term might be maintained well beyond the active intervention in a manner analogous to the persistent changes that follow intensive insulin treatment for people with type 1 diabetes," they said.
"We propose that lifestyle intervention should start much earlier, when people are normoglycemic, to achieve true primary prevention of type 2 diabetes and its main consequence, cardiovascular disease," they said.

Practice Pearl:
Explain to interested patients that this study found that lifestyle modifications reduced the risk of diabetes well beyond the end of the interventions
Li G, et al "The long-term effect of lifestyle interventions to prevent diabetes in the China Da Qin Diabetes Prevention Study: a 20-year follow-up study" Lancet May 24, 2008; 371: 1783-1789.

Lindstrom J, Uusitupa M, "Lifestlye intervention, diabetes, and cardiovascular disease" Lancet 2008; 371: 1731-1733.

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