LADA or Diabetes 1.5

Source: Diabetes Focus, Third quarter 2004
Author: Jeffrey Mahon, M.D., M.Sc., FRCPC

LADA or Diabetes 1.5 – Some 2 million people may not have type 2, but a less-understood form of autoimmune diabetes instead

Latent Autoimmune Diabetes in Adults (LADA), also called slow-onset diabetes or diabetes 1.5, has similarities both to type 1 and type 2. Often it is not recognized as LADA or type 1.5, because at first it looks like and reacts positively to treatments for type 2. However, it ends up revealing itself as an autoimmune form of diabetes, more like type 1. It’s a vexing issue, and we asked Dr. Mahon to help us understand the differences and similarities between LADA and the two other types of diabetes.

DF: By definition, LADA is adult-onset autoimmune diabetes.  Why isn’t it considered adult-onset type 1?

Dr.M: When people are diagnosed with LADA, they don’t have the classic features of type 1 diabetes. These include rapid weight loss in someone who is not already overweight and a tendency to ketoacidosis (increased acid levels in the blood and urine). Those with type 1 lose the ability to make insulin relatively quickly. People with LADA seem to lose the ability to make insulin faster than those who have type 2, but more slowly than those who have type 1. People with type 1 have antibodies to the beta cells in their blood. People with LADA have antibodies, too, and that indicates, at least in part, that LADA also results from an immune attack on the beta cells. But the fact that the beta cells are killed off pretty quickly in type 1 and much more slowly in LADA suggest that the immune system is acting differently in each case. So, for now at least, it’s reasonable to consider LADA as separate from both type 1 diabetes and type 2 diabetes.

DF: Why are people with LADA so often misdiagnosed as having type 2?

Dr.M: There are two reasons for this. First, when an adult needs treatment for high blood sugar but doesn’t have the classic features of type 1 diabetes, often we can bring glucose levels under control using exercise, diet and oral medications, just as we can for type 2 diabetes. In this way, the problem looks like type 2 diabetes. Second, testing for pancreas antibodies, which is needed to determine if a person has LADA, is not yet a routine clinical practice.

One could argue that it doesn’t matter. Our treatment wouldn’t change, since there are no immune-based treatments that are proven safe and effective in protecting their beta cells from further destruction.

The person with LADA still needs to be monitored and treated according to existing practice guidelines.  But sooner or later, glucose levels deteriorate to the point where the person needs insulin treatment to control his or her blood sugar. It may take one to six years before it becomes apparent that a person had LADA, and that usually happens when they become insulin-dependent.

Dr. Mahon is an associate professor of epidemiology at the University of Western Ontario, in London, Canada. Dr. Mahon is also the coauthor of a paper titled “Insulin Resistance in Latent Autoimmune Diabetes of Adulthood,” that was published last year in the N.Y. Academy of Science Annual.