In a Diabetes Special Issue of The Lancet, researchers demonstrate that group-based lifestyle interventions of diet and exercise for a period of six years may prevent or delay diabetes for up to 14 years following the intervention. It is not clear, however, that lifestyle interventions also reduce the incidence of cardiovascular disease (CVD) and mortality.

There have been several major clinical trials in various countries that have demonstrated how people with impaired glucose tolerances can reduce their likelihood of diabetes due to lifestyle interventions. Researchers, though, still have questions regarding the length of time after intervention that the strategies remain effective. To investigate this issue, Professor Guangwei Li, (China-Japan Friendship Hospital, Beijing, China), Dr Ping Zhang (Centers for Disease Control and Prevention, Atlanta, Georgia, USA), and colleagues conducted the China Da Qing Diabetes Prevention Outcome Study (CDQDPOS) - analyzing 20 years of patient follow-up data.

The patients who participated in the study all had impaired glucose tolerance and came from 33 clinics in China. In 1986, the researchers randomly assigned the patients to one of three lifestyle intervention groups (diet, exercise, or diet and exercise) or to the control group. Over a period of six years (until 1992), the patients experienced active intervention, and a 2006 follow-up provided data that would be used to assess the interventions' long-term effects on main outcomes such as diabetes incidence, CVD incidence and mortality, and all-cause mortality.

During the active intervention period, the combined lifestyle intervention group had a 51% reduction in incidence of diabetes compared to participants in the control group. Over the whole 20-year period, this effect was reduced to 43%. Intervention participants had an average annual incidence of new diabetes diagnoses of 7%, compared an 11% rate for control participants. After 20 years, 80% of those in the intervention group had diabetes and 93% of the control group did; intervention group participants suffered 3.6 fewer years with the disease than control group participants. The researchers, however, did not find a significant difference between the intervention and control groups when measuring the rates of first CVD events, CVD mortality and all-cause mortality.

"This study has shown that, in Chinese people with impaired glucose tolerance, group-based interventions targeting lifestyle changes such as diet and exercise produce a durable and long-lasting reduction in incidence of type 2 diabetes...Since around 3 million excess deaths a year are attributable to diabetes worldwide, lifestyle interventions seem to be a justifiable public-health action both in developed and developing nations," conclude the authors.

Dr Jaana Lindström (National Public Health Institute, Helsinki and University of Helsinki, Finland) and Professor Matti Uusitupa (University of Kuopio, Finland) write in an accompanying editorial that, "We propose that lifestyle intervention should start much earlier, when people are normoglycaemic, to achieve true primary prevention of type 2 diabetes and its main consequence, cardiovascular disease. In this regard, both population-based strategies and those targeted at high-risk groups should be applied."

The long-term effect of lifestyle interventions to prevent diabetes in the China Da Qing Diabetes Prevention Study: a 20-year follow-up study
G Li et al.
The Lancet (2008). 371[9626]: pp. 1783 - 1789.
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Written by: Peter M Crosta