It is a common saying among neurologists that what is good for the heart is also good for the brain. Not only is this true of exercise, maintaining a healthy weight, and keeping blood pressure within a healthy range, but now a study suggests that blood sugar levels lower than the usual diagnostic criteria for diabetes may be detrimental to brain health.
It has long been known that high blood sugar levels are damaging to the circulatory system, contributing to atherosclerosis (plaques in the arteries) and associated problems like nerve damage, eye and kidney problems, gum disease and even heart attack and stroke.
As a major organ, the brain is dependent on the circulatory system for oxygen and other compounds necessary for cell health. When circulatory health is impeded, the brain suffers.
In the new study conducted by the Australian National University and published in Neurology, 249 people age 60 to 64 each had brain scans four years apart. Those people with higher fasting blood sugar levels were found to have experienced more brain shrinkage in the four-year interval.
Participants who were not diabetic, but who had high blood sugar levels were shown to have experienced brain deterioration. (In the United States, diabetes is commonly diagnosed when fasting blood sugar reaches or exceeds 126 milligrams per deciliter.)
Researchers took into account other factors — such as smoking, alcohol use, age and high blood pressure — that could affect brain health. Even controlling for those factors, the researchers found that 6 to 10 percent of brain loss could be accounted for only by blood sugar levels.
Interestingly, another study in the journal Pediatrics recently showed a link between metabolic syndrome (which includes the insulin resistance seen in pre-diabetes) in teens with worsened brain functioning.
In older adults, numerous studies have shown links between high blood sugar, Type 2 diabetes and dementia. Until now, though, it was unknown whether people with non-diabetic blood sugar levels could experience the same results. The current research suggests that blood sugar ranges too low to be considered diabetes may in fact place people at risk for brain deterioration along with other complications.
So, what can you do? Basically, it's important to live a healthy lifestyle. Get exercise, eat well and keep your brain active. Make sure to have your doctor keep an eye on your blood sugar ranges, and know your numbers for blood sugar just as you would for cholesterol and blood pressure. If you have questions about your diet, consult a registered dietitian or your doctor.
Dr. Gregory Jicha is the McCowan Endowed Chair in Alzheimer's Disease at the University of Kentucky Sanders-Brown Center on Aging.