Is Type 1 diabetes dramatically more common than is widely understood? That’s the contention of Dr. David Leslie, Professor of Diabetes and Immunology at London University’s Blizard Institute.
In the United States, about 30 million people are said to have diabetes. Of those, about 1 million are diagnosed with Type 1, and the other 29 million are diagnosed with (or suspected of having) Type 2. But is that ratio accurate? Or does it reflect a misunderstanding of the nature of Type 1 diabetes?
Dr. Leslie thinks the real numbers “will definitely be different:”
“The number of people with Type 1 is probably much higher than we’ve accounted for. That 29 million – something like 2 million of them may have undiagnosed Type 1.”
The misdiagnosis of Type 1 diabetes is already a known problem. It’s easy for doctors to confuse Type 1 with Type 2, especially among adult patients and those displaying some of the indicators of the latter condition, such as obesity. A recent study from the University of Exeter last year showed that “38% of patients with Type 1 diabetes occurring after age 30 were initially treated as Type 2 diabetes,” and, even more strikingly, that “half of those misdiagnosed were still diagnosed as Type 2 diabetes 13 years later.”
According to Dr. Leslie, even these numbers may underreport the problem: “In our research, of those adults who presented with [Type 1] diabetes, the ratio of those that did not require insulin, compared to those who did, was about 3:1.”
Dr. Leslie is a recognized leader in the world of diabetes research, having served as principal investigator on several major European trials. We were first alerted to his work when a fascinating paper that he authored came across the ASweetLife desk: C-peptide persistence in type 1 diabetes: ‘not drowning, but waving’?
The paper, published in the journal BMC Medicine, discusses surprising amount of variance in C-peptide persistence in people with Type 1 diabetes. While it was once thought that everyone with T1D rapidly declined towards zero insulin production, what we now know is that C-peptide persistence varies widely across a spectrum. Most people with T1D retain at least some ability to produce insulin, even after many years, and many retain so much that they haven’t even been identified as having T1D.
And so the old image of T1D as a disease of the young is gradually getting turned on its head. Various studies have shown that among T1D patients requiring insulin immediately, just as many were diagnosed in adulthood as in childhood. That’s without counting the unknown millions that have a mild or slow-developing form of the disease and have yet to be identified.
Dr. Leslie told me, “I see patients every week who are diagnosed in adulthood and are told, ‘That’s it, Type 2, end of story.’ They don’t get the antibodies test. Every week I see people like that.” When Dr. Leslie tests them, he will often learn that they do have the autoantibodies that define Type 1 diabetes.
Dr. Leslie explained that it only became evident as late as the 1970s that adults were developing variants of Type 1 diabetes that did not require insulin. In the years since, researchers have begun to identify a bewildering diversity of specific types of Type 1 diabetes, each with their own unique criteria, such as LADA, MODY and SPIDDM. But even while awareness of adult-onset diabetes and these associated conditions has grown, many experts still tend to view Type 1 diabetes through the prism of our old understanding of it as a “juvenile” or “insulin-dependent” disease. It was only within the last decade, for example, that the Juvenile Diabetes Research Foundation officially changed its name to JDRF.
The old stereotypes are still strong. When I was diagnosed (as an adult) I had more than a few people express surprise that it was even possible for an adult to develop T1D. One too-confident acquaintance told me that I was in error, and that I had Type 2. Unfortunately, many on the front lines of diabetes, such as the primary care providers and family doctors that are often the first to see a patient with the symptoms of hyperglycemia, still cling to these old assumptions.
Dr. Leslie’s contention reminds us that proper diabetes management requires self-examination and self-advocacy. Diabetes is not a disease that allows one to simply accept a doctor’s prescription uncritically. Patients themselves have the primary responsibility of monitoring their own blood sugar levels and evaluating the success of their medicine, diet, lifestyle and exercise choices.
Sometimes, unfortunately, the need for self-advocacy extends even to question of the diagnosis itself.