The lede in a recent piece on USAToday sets the stage: “Higher blood sugar levels, even those well short of diabetes, seem to raise the risk of developing dementia, a major new study finds. Researchers say it suggests a novel way to try to prevent Alzheimer’s disease -- by keeping glucose at a healthy level.” The article was based on a study at the University of Washington, Seattle, and was published in the New England Journal of Medicine.
A piece by Megan Brooks in MedScape Medical News quotes the study’s lead author, Dr. Paul Crane, as saying, “We considered blood glucose levels far into the normal (nondiabetic) range, and even there found an association between higher glucose levels and dementia risk.” “He said the results suggest that the ‘clinical determination of diabetes/not diabetes may miss important associations still there for people who are categorized as not having diabetes’.”
The Associated Press story on the USAToday piece was written by Marilynn Marchione. She quotes Dallas Anderson, a scientist at the National Institute on Aging, the federal agency that paid for the study: “It’s a nice clean pattern -- risk rises as blood sugar does.” According to Marchione, Anderson said, “This is part of a larger picture” and adds evidence that exercising and controlling blood pressure, blood sugar and cholesterol are a viable way to delay or prevent dementia.
Marchione then also quotes Dr. Crane, “At least for diabetics, the results suggest that good blood-sugar control is important for cognition.” And, for those without diabetes, he said, “it may be that with the brain, every additional bit of blood sugar that you have is associated with higher risk. It changes how we think about thresholds, how we think about what is normal, what is abnormal.”
Charles Bankhead of The Gupta Guide at MedPageToday commented, “Nondiabetic patients who developed dementia had a mean blood glucose level of 115mg/dl in the preceding 5 years compared with 100mg/dl in similar patients who did not have dementia. According to Dr. Crane, “the higher levels were associated with almost a 20% [18% actually] increase in the hazard for dementia.”
This piece by Paula Span in The New York Times has another quote from Dr. Crane: “We found a steadily increasing risk associated with ever-higher blood glucose levels, even in people who didn’t have diabetes. There’s not threshold, no place where the risk doesn’t go up any further or down any further.” The association with dementia kept climbing with higher blood sugar levels and, at the other end of the spectrum, continued to decrease with lover levels. He said that this held true even at glucose levels considered normal, she said.
Another recent article from MedPageToday ties blood sugar (A1c) levels to cognitive function NOW, not to the far-off future risk of dementia. The group studied was a population of non-diabetics, aged 50 and up, with BMIs between 25 and 30. Their mean A1c was 5.8%, with a range from 4.3% to 6.5%. The researchers found that “each of the three cognition parameters evaluated was significantly associated with A1c levels…”
The article, titled “Blood Sugar Tied to Cognitive Function,” appeared in The Gupta Guide, Sanjay Gupta, MD, Editor, and was reviewed by staff of the Perlman School of Medicine at the University of Pennsylvania. The researchers “added that ‘lifestyle strategies’ to achieve strict glucose control could prevent age-related cognitive decline, even in individuals with A1c levels currently considered normal…”
So, what’s the takeaway? What does it mean to change “how we think about thresholds, how we think about what is normal, what is abnormal”? Well, well-designed prospective controlled trials are needed to prove causation, but the association of progressively higher and lower blood glucose with cognitive function, and ultimately dementia, even at so-called “normal” and “nondiabetic” blood sugar levels is undeniably true.
What is considered “normal”? And what is “prediabetic”? From 1979 to 1997 the threshold for type 2 was two consecutive visits with a fasting blood glucose of ≥140mg/dl. In 1997, ≥126mg/dl became the threshold for diabetes. In 2010 the ADA added A1c standards, with an A1c of 6.5% for diabetes (with a “treatment goal” of 7.0%!), and an A1Cs of 5.7--6.4% regarded as “pre-diabetic”. Some physicians, notably Richard K. Bernstein, consider 5.8% to be a full-blown type 2 diabetic. Another, Dr. Ralph DeFronzo, in his Banting lecture at the 2008 ADA convention, said that “By both pathophysiological and clinical standpoints, these pre-diabetic individuals with IGT should be considered to have type 2 diabetes.”IGT, or Impaired Glucose Tolerance, is defined as a fasting Oral Glucose Tolerance Test result of >140 at 2 hours. Statistically, you are 7-10 years away from diabetes and your heart disease risk is already rising. To test your glucose tolerance, follow the directions here: http://www.phlaunt.com/diabetes/14046889.php. But if there are no thresholds for an increased risk of dementia, shouldn’t we all adopt “‘lifestyle strategies’ to achieve strict glucose control” and thus potentially “prevent age-related cognitive decline, even in those individuals with A1c levels currently considered normal…”?