What's Your Type? With Diabetes, It Can Be Unclear
A drop in the number of newly-diagnosed diabetes cases is good public health news. But for the Type 1 diabetes community it's a source of frustration, because the numbers hide their story.
Last month, the Centers for Disease Control and Prevention announced that new cases of diagnosed diabetes among adults in the U.S. had finally dropped after decades of growth, from 1.7 million in 2008 to 1.4 million in 2014.
The decline in new cases gives "confidence that our diabetes prevention efforts are working and we are moving in the right direction," CDC officials said via email to Shots. "We know that long-term lifestyle changes in those at high risk are critical to prevent Type 2 diabetes and maintain this progress."
While it's certainly the right direction for the more common Type 2 diabetes, the findings don't apply to Type 1, a different condition that appears to be on the rise and that is not caused by obesity or lifestyle factors. Rather, Type 1 diabetes results from an autoimmune destruction of the insulin-producing cells of the pancreas.
And while Type 2 diabetes is linked to obesity and can typically be managed with diet, physical activity, and various medications including insulin for some, Type 1 always requires insulin treatment, either with multiple daily injections or an infusion pump, and is far more labor-intensive to manage.
Type 1 is believed to make up roughly 5 percent of the total 29 million adults and children in the U.S. who currently live with diabetes, or about 1.5 million people. But, the actual number isn't really known, and some surveys have suggested there may be twice that many.
The new CDC numbers came from the National Health Interview Survey (NHIS), which asked adult respondents whether a health professional had ever told them they have diabetes. The survey doesn't ask what type.
This is a problem, according to officials with the T1D Exchange, a nonprofit organization that includes a clinic network, registry, biorepository, and online patient community. In an open letter to the CDC, the Exchange's executive director Dana Ball and chief medical officer Dr. Henry Anhalt called for clarification of the announced decrease in new diabetes cases.
"Comingling of the data, particularly from the leading national public health institute of the United States, perpetuates the myth that diabetes is one disease sharing a name, while the reality is that Type 1 and Type 2 diabetes are actually two different diseases in the diabetes family," Ball and Anhalt wrote.
One concern, Anhalt told Shots, is that scientists seeking funding for research into Type 1 diabetes might be turned down if the condition is perceived to be on the decline, when in fact the opposite appears to be the case.
Most of the available data on Type 1 diabetes are in children, even though a large proportion of people with the condition are adults who developed it either as children or in adulthood.
In a large multisite study called SEARCH for Diabetes in Youth that is jointly funded by the CDC and the National Institute of Diabetes and Digestive and Kidney Diseases, there was a 21 percent increase in the number of new cases of Type 1 diabetes in children between 2001 and 2009. Increases were seen in kids of all ages, as well as in ethnic or racial minority groups that are more commonly associated with Type 2.
And according to the International Diabetes Federation's Seventh Atlas , released in 2015, the number of kids with Type 1 diabetes worldwide had risen 9 percent since the Sixth Atlas, from 2013.
Researchers don't know why Type 1 diabetes is rising, and it's important to find out, Anhalt said. "The call to action was not necessarily to say CDC is bad. But if you don't have a way to do it, find one, because obtaining those data is vital."
But that's not so easy, says Edward Gregg, chief of the Epidemiology and Statistics Branch in the CDC's Division of Diabetes Translation. "Our national survey data unfortunately don't have the detail necessary to accurately distinguish diabetes types," he told Shots.
For one thing, while the majority of adults with diabetes in the U.S. have clear-cut Type 2, many aren't familiar with the terminology or are confused about it. Because T1 used to be called "insulin-dependent" diabetes, some people still mistakenly believe that anyone treated with insulin has Type 1. In fact, between a quarter and a third of people with Type 2 are treated with insulin, typically after they've had the condition for several years.
And the former terms "juvenile" and "adult-onset" diabetes persist despite having been officially changed to Types 1 & 2 nearly 20 years ago, after it became clear that adults could develop the "juvenile" type. And Type 2 is now appearing in some overweight and obese children, particularly among African-American, Hispanic or Native American teenagers.
"When you survey people in the population you could ask them their type, but it would not be a super-accurate way of determining the prevalence," Gregg noted.
Health care providers are confused too. Some will simply diagnose all new-onset diabetes in adults as Type 2, since it wasn't appreciated until recently that Type 1 can and often does first appear in adults in their 20s, 30s, 40s, and even older. (Because Type 1 onset tends to be slower in adults, it's often called "latent autoimmune diabetes of adulthood," or "LADA.")
And for pediatricians, it may be difficult to tell which diabetes type an overweight or obese child or teenager has.
Indeed, the overall rise in obesity has furthered the diagnostic confusion. People with Type 1 were generally thin in the past, but today that's no longer the case (in the developed world, anyway).
Although obesity isn't the driver of Type 1 diabetes as it is in Type 2, people with Type 1 diabetes today are at least as likely to be overweight or obese as the general population. And with that, they may also display similar heart disease risk profiles as do people with Type 2 diabetes – in fact, heart disease is believed to be the number one killer of people with Type 1 diabetes, as it is for Type 2.
Adding to the confusion, there are other genetic types of diabetes that are also commonly misdiagnosed as either Type 1 or Type 2. Some of those people are put on insulin unnecessarily, making them vulnerable to weight gain and potentially dangerous low blood sugar episodes.
While some laboratory tests can help determine diabetes type, none are perfect and the most accurate one – checking for antibodies associated with Type 1 diabetes – is not routine and can be costly. (The genetic tests are even more expensive.)
Endocrinologist M. Sue Kirkman, a professor of medicine at the University of North Carolina, Chapel Hill, doesn't ask diabetes patients about their type. Instead, she asks about factors such as their age and symptoms at diagnosis, medication history and family history of diabetes.
"There's a lot of confusion, Kirkman says. "It's not infrequent to see medical records that say Type 2 diabetes, but when we ask the patient some of those questions it's clearly Type 1." And if the type still isn't clear, she'll order an antibody test.
While some argue that knowing the type may not matter as long as the person's blood sugars are well-controlled, mix-ups can have serious consequences. For example, in adult hospital settings, where Type 2 diabetes is extremely common, the fact that insulin can't be withheld for long periods of time – such as for a surgical procedure - in Type 1 patients may be overlooked, Kirkman notes.
Besides, she says, "I actually think it's important for people to understand what kind of diabetes they have, even if [their current treatment] is working. I think it's important to be educated about what's wrong with your body."
Kirkman agrees with the T1D Exchange that CDC should work to improve its data gathering. "I hope the CDC can in the future distinguish better, because I think it's really important to know what's going on with one and the other."
In fact, Gregg says, CDC is addressing the issue in several ways. His team has developed new questions for the NHIS aimed at better distinguishing between the diabetes types, including the age at diagnosis, the interval between diagnosis and starting insulin (a short time would suggest Type 1), and whether insulin use was ever stopped (a long period without insulin would suggest Type 2).
Those questions are being field tested, he said, noting that "we'd be getting a better estimation of proportion of Type 1 versus Type 2, although it won't be perfect."
And, in addition to co-funding the SEARCH study, which looks at both Type 1 and Type 2 diabetes in youth, CDC has also recently issued a request for applications for research specifically to investigate rates of Type 1 diabetes in young adults, with a due date of February 23rd. "That would also hopefully fill this data gap," Gregg said.
Meanwhile, some diabetes experts say that it's time for a complete overhaul of the way diabetes is classified by basing it on underlying causes rather than potentially misleading descriptive characteristics.
In a perspective published last week in the American Diabetes Association journal Diabetes Care, the authors wrote, "The current classification system presents challenges to the diagnosis and treatment of patients with diabetes... in part due to its conflicting and confounding definitions of Type 1, Type 2, and [LADA]...We urge that the time is right to convene a committee of diabetes community leaders and researchers to reevaluate the current outmoded [diabetes] classification system."
Miriam E. Tucker is a freelance journalist specializing in medicine and health. You can follow her on Twitter @MiriamETucker.
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