Should more classifications be available for different varieties of diabetes?

By Pam Sowers
HS News and Community Relations

One out of four people over age 45 is likely to have diabetes. According to the latest studies, that should put most of the Baby Boomers in line at the doctor’s office, ready for a blood sugar test. Once the diagnosis is made, however, a UW researcher and clinician says they may not fall into the two categories of the disease established by the American Diabetic Association in 1979.

In an editorial published in volume 17 of the journal Clinical Diabetes, Dr. Irl Hirsch, medical director of the Diabetes Care Center at UW Medical Center and associate professor of medicine, says the old classifications resulted in classifying patients by treatment, rather than by the causes of the specific disease.

Irl Hirsch, medical director of UW Medical Center’s Diabetes Care Center. Photo by Gavin Sisk

The ADA has classified insulin-dependent diabetes mellitus as type 1, and non-insulin-dependent diabetes mellitus as type 2. Hirsch says recent research shows what has been called type 1, or juvenile onset diabetes, is actually an auto-immune response.

On the other hand, patients with type 2 diabetes are resistant to the effects of insulin. Complete insulin deficiency does not develop in these people, and there is no evidence of any autoimmune disorder.

The cause of the development of high blood sugar is often unclear. From 10 percent to 20 percent of patients who develop diabetes as adults have what has been called latent auto-immune diabetes of adults, or LADA. Typically, these people are 35 years old or older, not overweight, and may continue on medication for several years before becoming insulin-dependent. Hirsch prefers to call these patients type 1.5, to be consistent with the ADA’s current nomenclature.

Complicating the matter is another group of patients who have diabetes, but when started on insulin have only a gradual loss of the ability to produce their own insulin. Some of them can be maintained on extremely low doses of insulin for years. Hirsch says this “honeymoon” period, more typical of newly diagnosed children with type 1 diabetes, should not be taken as a signal to try oral medication; however, these patients do not have type 1.5 either. Hirsch sees these patients as type 1.25.

“It turns out you can get this at any age,” Hirsch adds. “The oldest person I’ve seen with a fresh diagnosis was 86 years old. We now know it can take years for the body to destroy the cells that produce insulin.”

Hirsch’s advocacy of these new subclassifications may send the ADA nomenclature committee back to the drawing board, to allow for variations in the standard descriptions.