Long-term exposure to increased glucose levels is known to cause damage to the kidneys, retinas and other organs. Now, it appears that long-term exposure to hyperglycemia may also have significant and measurable effects on the brain, and greater efforts are needed to evaluate and monitor patients with diabetes for dementia and Alzheimer’s disease, according to experts.
“I think we all need to have our antenna up. It is a risk, and we need to get our patients into evaluation and treatment centers when we begin to see the problem,” said endocrinologist Janet McGill, MD, who is a professor of medicine in the division of endocrinology, metabolism and lipid research at Washington University School of Medicine in St. Louis. “Do we need wholesale random screening? That may not be cost-effective, but we need to be aware of the early signs.”
Diabetes Effects’ on the Brain
A recent review published in the American Journal of Psychiatry has found that individuals with mild cognitive impairment (MCI) are at higher risk for developing dementia if they have diabetes or psychiatric symptoms such as depression.1
Researchers at University College London analyzed data from 62 separate studies, following a total of 15,950 people diagnosed with MCI. They found that among patients with MCI, those with diabetes were 65% more likely to progress to dementia. The review further suggests incorporating appropriate preventative strategies to lessening the increasing societal burden of dementia in older adults with diabetes.
Another study conducted by researchers at the Mayo Clinic has also found that individuals who develop diabetes and high blood pressure (BP) in middle age are more likely to have brain cell loss and other damage to the brain. In addition, patients with diabetes were found to be more likely to have problems with memory and thinking skills compared with individuals without diabetes or hypertension, according to the study published in Neurology.2
Study author Rosebud Roberts, MB, ChB, who is an epidemiologist at the Mayo Clinic in Rochester, Minnesota, said by controlling diabetes and hypertension in middle age, it may be possible to prevent or delay the brain damage that occurs decades later leading to memory problems and dementia.
Dr. Roberts and her colleagues evaluated the thinking and memory skills of 1,437 people with a median age of 80 years. The participants had either no thinking or memory problems or MCI. In this study, middle age was defined as age 40 to 64 years and old age was defined as age 65 years and older.
Brain scans revealed that individuals who developed diabetes in middle age had smaller total brain volume by an average of 2.9% compared with those without diabetes. In the hippocampus, the volume was 4% smaller.
According to the data, patients with diabetes were also twice as likely to have thinking and memory problems. Dr. Roberts said patients who developed diabetes even in old age were more likely to have areas of brain damage. Conversely, not many effects related to high BP were noted that developed in old age.
These findings suggest that diabetes has adverse effects regardless of the age at which the disease develops, she said.
“We concluded that midlife type 2 diabetes was not simply a vascular risk factor but rather had a more general negative effect on brain integrity. It could directly affect nerve cell and synapse physiology, perhaps by enhancing Alzheimer-type neurodegeneration, or the loss of brain volume could be separate though additive with Alzheimer pathology,” said study co-author David Knopman, MD, in an interview with Endocrinology Advisor. “We do not know whether the issue is simply elevated blood glucose, elevated HbA1c, the degree of insulin resistance or something else that is the fundamental culprit.”