Diabetes Dateline
Summer 2006

Research News

Nearly One-third of U.S. Adults With Diabetes Don’t Know They Have It

The percentage of adults aged 20 and older with diagnosed diabetes rose from 5.1 to 6.5 percent in recent years while 30.1 percent of U.S. adults with diabetes don’t know they have it, according to a study by the National Institutes of Health and the Centers for Disease Control and Prevention.

The study found that the number of people with undiagnosed diabetes and pre-diabetes stayed the same.

About 26 percent of adults had a form of prediabetes, or impaired fasting glucose (IFG). The study, based on data from the National Health and Nutrition Examination Survey, was published in the June 2006 issue of Diabetes Care.

“With the rising number of people diagnosed with diabetes, we had hoped there would be a corresponding decrease in the number of undiagnosed diabetes cases, but that was not the case,” said lead study author Catherine Cowie, Ph.D., director of the diabetes epidemiology program at the National Institute of Diabetes and Digestive and Kidney Diseases. “When you add it all up—those with diagnosed diabetes, undiagnosed diabetes, and pre-diabetes—you get 73 million people with diabetes or on their way to getting it. It’s really daunting.”

Pre-diabetes, which usually has no symptoms, is dangerous. Many people who have it develop type 2 diabetes within 10 years. Pre-diabetes also substantially raises the risk of a heart attack or stroke even if it doesn’t progress to type 2 diabetes, which accounts for up to 95 percent of all diabetes cases and almost all cases of undiagnosed diabetes.

Early diagnosis of pre-diabetes is important for preventing or delaying the onset of type 2 diabetes.

“We need to do a better job of getting out there and teaching health care providers to test for pre-diabetes or type 2 diabetes on a routine basis,” Cowie said. “And people at risk need to take it upon themselves to get their health care providers to test them.”

Diagnosing type 2 diabetes early allows patients to receive treatment preventing complications before the disease progresses too far.

Diabetes risk factors include age, excess weight, family history, belonging to a minority group, and having had gestational diabetes.

Study Shows No Link Between Tight Diabetes Control and Cognitive Impairment

The landmark Diabetes Control and Complications Trial (DCCT), sponsored by the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), which followed 1,441 people with type 1 diabetes for a decade until 1993, showed conclusively that tight blood glucose control significantly reduces the risk of developing diabetes complications, such as eye, kidney, and nerve disease.

But the DCCT also showed that patients in the trial who kept their blood glucose levels as close to the normal range as possible were three times as likely to suffer episodes of severe hypoglycemia—abnormally low blood glucose levels that can cause confusion, irrational behavior, convulsions, and unconsciousness. This finding raised the fear that although tight blood glucose control may lower the risk of developing other diabetes complications, it also might lead to a long-term loss of cognitive ability.

After following three-quarters of the original DCCT participants for an additional 6.5 years, however, researchers from the Joslin Diabetes Center, in collaboration with investigators at the University of Pittsburgh Medical Center, George Washington University, and the DCCT/EDIC (Epidemiology of Diabetes Interventions and Complications Study) Research Group, found no link between multiple severe hypoglycemic reactions and impaired cognitive function in people with type 1 diabetes.

To determine whether tight control has long-term adverse effects on cognitive function, the researchers examined 1,059 participants in the original DCCT trial: 537 patients receiving intensive therapy with either an insulin pump or three or more daily insulin injections; and 522 patients receiving conventional therapy of one or two injections daily. For the period of this study, 652 patients reported no hypoglycemic, or low blood glucose, events resulting in coma or seizure; 348 reported from one to five events; and 59 patients reported more than five.

All of the patients were evaluated using the same neuropsychological tests that researchers administered during the DCCT trial, tools that analyzed abilities in eight cognitive domains: problem solving, learning, immediate memory, delayed recall, spatial information, attention, psychomotor efficiency, and motor speed. Adjusting for age, sex, years of education, length of follow-up, and the number of cognitive tests taken, researchers found no change in any of the eight areas.

“The DCCT led to a paradigm shift in the treatment of type 1 diabetes,” said Catherine Cowie, Ph.D., the NIDDK’s director of the diabetes epidemiology program. “Today, more than 20 years after it was launched, it continues to provide invaluable insights.”

Diabetes Prevention Trial Sheds Light on Metabolic Progression Patterns

Over a period of at least 2 years, glucose tolerance gradually deteriorates as stimulated C-peptide levels slowly decline in a substantial number of people who develop type 1 diabetes, according to a study of metabolic progression patterns to type 1 diabetes. The study, which provided the first systematic analyses of glucose and C-peptide trends preceding the diagnosis of type 1 diabetes, used data from the Diabetes Prevention Trial–Type 1. The data showed that glycemia levels begin to increase at least 2 years before diagnosis, after which glucose levels continue to increase gradually until at least 6 months before diagnosis. Within 6 months of diagnosis, a steeper rise in glucose levels occurs. As the glycemia level increases, fasting C-peptide levels stay constant and even increase at diagnosis. The article, “Patterns of Metabolic Progression to Type 1 Diabetes in the Diabetes Prevention Trial–Type 1,” appeared in the March 2006 issue of Diabetes Care.

[Top]

NIH Publication No. 06–4562
September 2006