How dangerous is prediabetes? It’s tough to say. The condition has only been recognized for about one decade, and there’s plenty of debate within the medical community about how meaningful it is.
Within the last month, three different notable studies looked at the health impacts of prediabetes. They came to apparently contradictory conclusions.
Prediabetes has been controversial for the entirety of its short history as a recognized condition, which began when American Diabetes Association (ADA) officially named and defined the term in 2009. In doing so, the ADA contradicted the recommendations of an international committee of experts it had helped to convene on the subject. Other major diabetes organizations, including the European Association for the Study of Diabetes and the International Diabetes Federation, took the advice of the same panel, and as a result there is global disagreement on how to name or define the condition.
In 2016, The Journal of Clinical Endocrinology & Metabolism published a Position Statement “strongly” recommending that prediabetes be redefined much more narrowly, so as to be limited only to individuals at the highest risk of developing full-blown diabetes. The authors argued that defining prediabetes too broadly—about 88 million American adults are thought to have the condition, according to the ADA criteria—includes far too many patients that are not really at serious risk of disease progression.
A 2019 exposé in Science magazine went further, alleging that the very term “prediabetes” was essentially a marketing creation, a new medical condition concocted by the ADA and its pharmaceutical industry allies in order to create tens of millions of new potential customers.
And yet, there’s very little dispute that prediabetes is at least a potentially significant condition. While there is global agreement on the bright line defining diabetes, the hyperglycemia and insulin resistance that define diabetes are continuous risk factors, and the border between health and dysfunction can never be strictly delineated. A patient with an HbA1c 6.4% (prediabetes) is likely to benefit from improved glycemic control for the same reasons that a patient with an HbA1c of 6.5% (diabetes) would.
“Less of a worry than once believed”
The first new study, published in JAMA Internal Medicine, received a high-profile treatment from The New York Times. As the sub-headline states, the study suggested that prediabetes “might be less of a worry than once believed,” at least for one demographic—the elderly.
The study looked at older adults (average age: 75.6) without diabetes and followed them for up to 6.5 years. While a majority (73%) of adults satisfied at least one definition of prediabetes when the study commenced, very few actually developed full-blown diabetes. Older adults with prediabetes were actually more likely to experience a blood sugar drop to healthy levels than they were to experience a negative progression to T2D. Those with prediabetes were no more likely to die during the study than those without it.
The takeaway, according to experts interviewed by the Times, is that prediabetes shouldn’t be much of a priority for older adults. It’s not terribly likely to turn into diabetes—and even if it does, patients are not likely to live long enough to suffer the worst complications. And, the argument goes, the elderly often already have more important health issues to concern themselves with.
Not so fast
It’s important to underline, however, that the study really only applies to the very old. People with prediabetes at middle-age have, at best, a “substantially increased risk” of developing diabetes within the next five years. It might be even worse for young adults and adolescents; T2D is known to be especially aggressive in younger patients. And the younger the patient, the more time he or she has to develop (and suffer from) the debilitating long-term consequences of diabetes.
The JAMA study profiled in the Times assessed how likely prediabetes was to progress to diabetes; but it did not attempt to probe whether or not prediabetes is dangerous in and of itself. Two other recently published studies may raise concerns on that subject.
First, in Diabetes Care, a team of researchers analyzed data from older Swedish adults (average age: 72) to see if prediabetes would lead to physical decline and disability progression. And in fact, it did. Patients with prediabetes—even those that did not develop full-blown Type 2 diabetes—showed statistically significant functional decline in physical aptitude tests and a greater frequency of disabilities (defined as difficulty with common tasks such as dressing, bathing, grocery shopping and managing medications). Participants with prediabetes had lower scores when the study began, and still experienced larger declines over the years that the study covered. Some of this decline may be due to the higher rate of cardiovascular disease that those with prediabetes suffered—itself an obvious reason for concern.
Second, in Diabetes, Obesity and Metabolism, a British study addressed the relationship between glycemic control and brain health across the glycemic spectrum. In this study, participants were somewhat younger (ages 40-69), but the finding was much the same: prediabetes was associated with significant risk increases. Those with prediabetes suffered from statistically significant risks of vascular dementia and cognitive decline. Prediabetes even affected the composition of the brain, leading to greater concentration of white matter hyperintensities (brain lesions) and a reduced hippocampal volume.
It’s good news that older adults with prediabetes only rarely develop Type 2 diabetes. Nevertheless, we’d urge caution before concluding that prediabetes isn’t problematic enough to represent a health priority for the elderly. Elevated glucose levels—and the insulin resistance that causes them—do not begin to harm the body only after one passes the threshold for Type 2 diabetes. As the recent studies on physical and cognitive function show, hyperglycemia negatively impacts many aspects of our health, and its risks occur across the whole glycemic spectrum.