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Serious Health Risks From Impaired Glucose Tolerance

IGT and IFG are major risk factors for future diabetes and cardiovascular disease (CVD) and the need for urgent intervention. " BRUSSELS, BELGIUM — September 11, 2002 — The statement represents a milestone consensus", said Professor Sir George Alberti, President of the IDF. "Cardiovascular diseases are the major cause of premature death in individuals with diabetes. Cost-effective strategies must be developed to identify IGT and IFG in high-risk populations so that prevention can be targeted to where it matters most."

The statement calls for IGT and IFG to be taken seriously by health authorities and for screening and treatment to be reimbursable. IGT and IFG should be considered as seriously as hypertension, dyslipidaemia and obesity in relation to diabetes risk and classified as treatable risk factors.

IGT and IFG are categories of glucose intolerance, an intermediate state between normal glucose tolerance and type 2 diabetes.

Sixty percent of people with diabetes have either IGT or IFG five years before they are diagnosed(1). A study in America suggested that one in seven adults aged over 40 years with no history of diabetes has IGT while one in twelve have IFG(2). In total it is estimated that over 200 million people worldwide have IGT.

Seventy-five per cent of people with diabetes will die as a result of CVD(3), making CVD the major cause of premature death in people with diabetes. CVD may begin to develop well before type 2 diabetes is diagnosed. By the time type 2 diabetes is diagnosed 50 percent of people already have cardiovascular complications(3). People with diabetes are two to four times more likely to suffer a heart attack than people without diabetes(3)

The statement, published in this month’s edition of Diabetic Medicine, was released following an Expert Consensus Meeting convened by the IDF in response to the excessive cardiovascular risk seen in IGT and diabetes. The meeting was co-chaired by Professor Sir George Alberti, president of the International Diabetes Federation, professor of medicine at the University of Newcastle and professor of metabolic medicine at Imperial College, and Professor Paul Zimmet, director of the International Diabetes Institute, Melbourne, Australia.

People who are particularly at risk for the development of type 2 diabetes include those who are overweight, inactive, older, have a family history of diabetes or are from certain ethnic groups. The authors emphasise the effectiveness of lifestyle interventions such as weight loss and increased physical activity, which are highly effective in preventing or delaying the onset of diabetes in people with IGT. The Finnish Diabetes Prevention Study(4) and the Diabetes Prevention Programme(5) — two randomised controlled trials of individuals with IGT — found that lifestyle interventions can reduce the risk of progressing to diabetes by 58 percent. More trials are urgently needed to study the effect of lifestyle and drug interventions on the progression of IGT to diabetes.

The largest such trial in progress is NAVIGATOR, a world-wide study investigating the effectiveness of Starlix® (nateglinide), an oral hypoglycaemic agent, and Diovan® (valsartan), an angiotensin II receptor blocker in 7,500 people with IGT and at least one other cardiovascular risk factor (e.g. hypertension, raised cholesterol) or disease (e.g. angina, previous heart attack). Another international study, DREAM, is investigating the effectiveness of ramipril and rosiglitazone in the prevention of diabetes in over 4,000 people with IGT.

In studies including Stop-NIDDM6 and the Diabetes Prevention Programme(5), medical intervention with acarbose and metformin has been shown to reduce progression to diabetes in people with IGT. These studies have shown pharmacological interventions to be less effective than the intensive lifestyle interventions that were used in the Finnish Diabetes Prevention Study(4) and the Diabetes Prevention Program(5). More trials are urgently needed.

"We need more studies on lifestyle and drug intervention in people with IGT to reduce the massive burden that diabetes and CVD place on our lives and our health systems", said Professor Paul Zimmet. "Diabetes is the biggest epidemic the world will face in this century. Because of this, larger studies are required to investigate the effectiveness of additional drug interventions in preventing diabetes and CVD. We eagerly await the results of trials such as NAVIGATOR and DREAM to further investigate whether it is possible to prevent or delay diabetes in those at high risk". Diabetes Care 1998;21:1720-5.

References:
1. de Vegt F, Dekker JM, Stehouwer CD, Nijpels G, Bouter LM, Heine RJ. The 1997 American Diabetes Association criteria versus the 1985 World Health Organization criteria for the diagnosis of abnormal glucose tolerance: poor agreement in the Hoorn Study. Diabetes Care 1998;21(10):1686-90.
2. Harris MI, Flegal KM, Cowie CC, Eberhardt MS, Goldstein DE, Little RR, Wiedmeyer H-M, Byrd-Holt DD. Prevalence of diabetes, impaired fasting glucose and impaired glucose tolerance in US adults. The Third National Health and Nutrition Examination Survey, 1988-1994. Diabetes Care 1999; 21:518-528.
3. Donnelly R et al. Vascular complications of diabetes. Brit Med J 2000; 320: 1062-6.
4. Tuomilehto J, Lindstrom J, Eriksson JG, Valle TT, Hamalainen H, Ilanne-Parikka P, et al. Prevention of type 2 diabetes mellitus by changes in lifestyle among subjects with impaired glucose tolerance. New England Journal of Medicine 2001;344(18):1343-50.
5. Knowler WC, Barrett-Connor E, Fowler SE, Hamman RF, Lachin JM, Walker EA, et al. Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin. New England Journal of Medicine 2002;346(6):393-403.
6. Chiasson J, Gomis R, Hanefeld M, Josse R, Karasik A, Laakso M. The STOP-NIDDM Trial: an international study on the efficacy of an alpha-glucosidase inhibitor to prevent type 2 diabetes in a population with impaired glucose tolerance: rationale, design, and preliminary screening data. Study to Prevent Non-Insulin-Dependent Diabetes Mellitus.