Type 1 diabetes diagnosed in adulthood may be a form of slowly-progressing diabetes called latent autoimmune diabetes in adults (LADA). LADA is also known as slow-onset type 1 diabetes, type 1.5 diabetes, late-onset autoimmune diabetes of adulthood, and even “double diabetes,” since it has elements of both type 1 and type 2 diabetes. LADA patients, however, are closer to type 1 patients, because they will test positive for antibodies against insulin-producing beta cells of the pancreas.
LADA is more common than classic childhood type 1 diabetes, and is similar to type 1 diabetes, but presents more slowly—and therefore does not require insulin therapy as early in the course of treatment. Most LADA patients do eventually require insulin; the key difference between LADA and type 1 diabetes is not the age of disease onset, but rather the progression of the disease. People with type 1 diabetes tend to be completely insulin-dependent within a few months of diagnosis, while people with LADA can sometimes survive for years without needing to take insulin.
Because they still produce some insulin, and because the disease usually occurs in people over the age of thirty without severe symptoms, many LADA patients are initially misdiagnosed with type 2 diabetes. In fact, researchers estimate that up to 10 percent of people diagnosed with type 2 diabetes have LADA. LADA can be distinguished from type 2 diabetes by antibody tests. Patients who are antibody-positive have an autoimmune reaction similar to that of type 1 diabetes, but which is not found in type 2 diabetes.
Researchers still don’t know whether autoimmune diabetes in adults is due to the same underlying disease process as type 1 diabetes in children, and there are many LADA questions that still need answers. In an attempt to standardize the definition of LADA, the Immunology of Diabetes Society recently proposed the following criteria: patients should be at least thirty years of age, positive for at least one of four antibodies commonly present in type 1 diabetic patients, and untreated with insulin within the first six months of diagnosis.
No one can predict exactly how long a LADA patient will continue to produce insulin. For some, like dLife columnist Jessica Apple, the slow process of beta-cell destruction had probably been ongoing for close to a decade. The crucial task for the physician is to avoid missing a LADA diagnosis. Once LADA is diagnosed, the physician should recognize that some LADA patients require insulin, but because of the similarities to type 2 diabetes, they may benefit from concurrent treatment with various oral medicines.
Regardless of your age, if you are labeled as having type 2 diabetes but have no family history of diabetes and are not overweight, you may, in fact, have LADA. Your doctor can check for this with a blood test for autoantibodies and c-peptide levels, which indicate the amount of insulin you are producing (a low c-peptide level suggests LADA).
Jessica Apple is the co-founder and editor-in-chief of the online diabetes magazine ASweetLife.org. Her essays and stories have appeared in many national publications, including The New York Times Magazine, Financial Times, and The Southern Review. She and her husband both have autoimmune diabetes.