By Peter Galvin, MD
Prediabetes is an intermediate stage of blood sugar elevation that may precede type II diabetes. It affected approximately 720 million people worldwide in 2021 and is estimated to affect 1 billion by 2045. In the U.S., about 10% of those with prediabetes will progress to outright diabetes each year. The diagnostic criteria used to define prediabetes differs slightly depending on various agencies or associations setting the criteria. These criteria include the fasting glucose level, impaired glucose tolerance, and the glycosylated hemoglobin A1c. As a test for the initial diagnosis of diabetes or prediabetes, HbA1c has the advantage of convenience (no fasting required) compared to fasting glucose level or glucose tolerance test. However, HbA1c may be unreliable as a measure of time-averaged blood glucose levels under certain conditions such as hemolytic anemia, iron deficiency anemia, hemoglobinopathies, pregnancy, and uremia. Moreover, ethnic differences in HbA1c, independent of blood glucose levels, have been reported. Studies have shown that for given levels of blood glucose, black individuals will have higher levels of HbA1c than white individuals. The reasons for this discrepancy are unknown.
The American Diabetes Association (ADA) defines prediabetes as a fasting glucose of 100 to 125, glucose tolerance test results of 140 to 199, or a HbA1c level of 5.7% to 6.4%. The U.S. Preventive Services Task Force recommends screening adults aged 35 to 70 who are overweight or obese for prediabetes every three years. The ADA recommends universal screening for adults aged 35 and over every three years regardless of risk factors. In a large study of the U.S. population, fasting glucose levels identified 28.3% of individuals as having prediabetes, as compared to 21.7% for HbA1c, and 13.3% for a glucose tolerance test. Because of the instability of prediabetic states (false positives are not uncommon), most guidelines call for at least two, if not three, separate tests before confirming the diagnosis. Once an individual has been diagnosed as having prediabetes, annual monitoring is recommended. The major predictive factors for prediabetes include overweight or obesity (defined by the WHO as a BMI or 25.0 to 29.9 for overweight and >30 for obese), older age, physical inactivity, unhealthy diet, and genetic predisposition.
A national survey of U.S. adults aged 18 and over conducted between 2017 and 2020 showed a prediabetes prevalence of 38% in the overall population. Given the fact that obesity rates in the U.S. are climbing, especially among children and adolescents, this rate is expected to rise. Once the treatment of prediabetes has begun, the goal, of course, is the prevention of conversion into outright diabetes type II. The primary treatment is lifestyle modification, which includes weight loss, changing to a healthier diet (i.e., Mediterranean diet), and the institution of an exercise program, all of which should be in conjunction with the knowledge and consent, if not advice, of your healthcare provider. Some studies have shown benefit from the early initiation of treatment with metformin, however metformin alone is not nearly as effective as lifestyle improvement.
When one considers that diabetes is associated with major cardiovascular events, kidney failure, blindness, and premature death, a diagnosis of prediabetes should be a loud wake up call to start living healthier. Please direct questions and comments to firstname.lastname@example.org