NEW ORLEANS — Nearly a quarter of people aged 50 years or older with cardiovascular disease or aged 55 or older with at least one cardiovascular-disease risk factor had diabetes in a study that screened over 35,000 people.
Another 28% of the people in this screened group were found to have impaired glucose tolerance, Dr. M. Angelyn Bethel, an endocrinologist at Duke University, Durham, N.C., and her associates reported in a poster at the annual scientific sessions of the American Heart Association.
In addition, a risk assessment based on history, physical-examination findings, and common blood measures such as lipids and fasting glucose was able to identify three-quarters of the people diagnosed with diabetes using an oral glucose tolerance test. In contrast, identifying people as having metabolic syndrome based on the current U.S. definition was a relatively poor method for predicting who would be diagnosed with diabetes, the researchers reported.
They used data collected in the Nateglinide and Valsartan in Impaired Glucose Tolerance Outcomes Research (NAVIGATOR) trial, a study that began in 2002 and is planned to end next August. The study, sponsored by Novartis, which markets nateglinide (Starlix) and valsartan (Diovan), enrolled about 9,300 people with impaired glucose tolerance. They were aged 50 or older and diagnosed with cardiovascular disease or were aged 55 or older and had at least one cardiovascular disease risk factor such as hypertension, hypercholesterolemia, or current smoking.
The study's primary end point is prevention of diabetes and cardiovascular events.
To find participants for the study, Dr. Bethel and her associates screened more than 42,000 people who met the age and cardiovascular-disease history requirements in 39 countries. Their average age was 62 years, about half were women, and their average body mass index was about 29 kg/m
They screened these people with an oral glucose tolerance test, with valid results available for 35,744 people.
Of those screened, 22% had outright diabetes; 28% had impaired glucose tolerance, defined as a fasting glucose level of less than 126 mg/dL and a blood glucose level 2 hours following oral challenge of 140-199 mg/dL; 30% had impaired fasting glucose, meaning their fasting glucose level was 100-126 mg/dL but their glucose level 2 hours after oral challenge was less than 140 mg/dL; and the remaining 20% had normal glucose tolerance, with a fasting level of less than 100 mg/dL and a 2-hour level following challenge of less than 140 mg/dL.
These statistics showed the high prevalence of both diabetes and impaired glucose tolerance in the type of people eligible for screening in the study, said the reseachers.
Their next goal was to find factors that could identify people with the type of history used by the study who had an especially high risk for diabetes. It would be impractical to use an oral glucose tolerance test on everyone with this history because of cost and inconvenience, they said.
The presence of metabolic syndrome, defined using the criteria of the Adult Treatment Panel III guidelines of the U.S. National Cholesterol Education Program, was only slightly better than flipping a coin, identifying 58% of those with diabetes. In contrast, an assessment taking into account several risk factors including sex, age, blood pressure, triglyceride level, LDL cholesterol level, fasting glucose level, and a history of cardiovascular disease events accurately identified 75% of those who had diabetes when they were assessed with an oral glucose challenge.
Middle-aged or older people with such a risk profile are good candidates for an oral glucose tolerance test that would provide an early diagnosis of diabetes, they said.