Prediabetes is a condition in which blood glucose levels are elevated, but not yet within the range classified as diabetes. It is also known as impaired fasting glucose (IFG) or impaired glucose tolerance (IGT). The new term was inaugurated by the U.S. Department of Health and Human Services (HHS) and the ADA in March 2002 to promote public understanding of this increasingly widespread problem. According to the American Association of Endocrinologists (AACE), roughly 57 million Americans had prediabetes in 2008. Studies have shown that most people with blood glucose levels in the prediabetes range go on to develop Type 2 diabetes within 10 years; the condition also raises the risk of having a heart attack or stroke by 50%. Prediabetes can be controlled, and in many cases even reversed, through lifestyle changes.
Prediabetes can be detected by either of the two standard tests currently used to diagnose diabetes. In the fasting plasma glucose test (FPG), a person fasts overnight and then has blood drawn for testing first thing in the morning, before he eats. People with a fasting blood glucose level of 100 to 125 mg/dl are considered to have prediabetes. A fasting blood glucose level over 125 mg/dl indicates diabetes. (A second test must be done on a subsequent day to confirm a diagnosis of diabetes.)
In the oral glucose tolerance test (OGTT), a person’s blood glucose is tested once after an overnight fast and again two hours after he has consumed a special, glucose-rich drink. A normal blood glucose level two hours after the drink is below 140 mg/dl; an elevated blood glucose level in the range of 140 to 199 mg/dl indicates impaired glucose tolerance, or prediabetes. A blood glucose level 200 mg/dl or higher two hours after the drink indicates diabetes. (Again, a second test must be done on a subsequent day to confirm diabetes.)
People who are overweight (defined as having a body-mass index of 25 or higher) and are age 45 and up are considered at risk for prediabetes and should be screened. People under the age of 45 who are overweight should also be screened if they have one or more of the following risk factors for diabetes: high blood pressure, a family history of diabetes, low high-density lipoprotein (HDL, or “good”) cholesterol and high triglycerides, a history of gestational diabetes or giving birth to a baby over 9 pounds, or belonging to one of the racial or ethnic groups that is at increased risk for Type 2 diabetes (African-Americans, Native Americans, Asian Americans/Pacific Islanders, and Hispanic Americans/Latinos). If a person is tested for prediabetes and his results are within the normal range, the ADA recommends that he be retested every three years. If a person is diagnosed with prediabetes, he should be screened for Type 2 diabetes every one to two years.
Prediabetes can also affect children and adolescents. A study published in The New England Journal of Medicine in March 2002 found that 25% of obese children and 21% of obese adolescents tested had blood glucose levels within the prediabetes range. Currently, not much is known about how to prevent or delay the onset of Type 2 diabetes in children. The widespread screening of younger people for prediabetes, therefore, is not currently called for by major health organizations. However, in 2000, the American Academy of Pediatrics recommended diabetes testing for obese children who also have two or more of the additional risk factors for diabetes mentioned earlier.
Not all cases of diabetes can be prevented, but many can, and ongoing research may point the way toward preventing even more.