Older adults with diabetes who experience severe episodes of low blood sugar, or hypoglycemia, are at increased risk of developing Alzheimer’s disease and other forms of dementia, a new study shows. And those with diabetes and dementia are more likely to experience hypoglycemia.
The results suggest that hypoglycemia and dementia can create a vicious cycle, in which low blood sugar damages the brain, which in turn makes people less able to manage their diabetes, leading in turn to more episodes of low blood sugar. "Older patients with diabetes may be especially vulnerable to a vicious cycle in which poor diabetes management may lead to cognitive decline and then to even worse diabetes management," said Dr. Kristine Yaffe, the senior author.
The findings, which appeared in the journal JAMA Internal Medicine, add to a growing body of evidence linking Type 2 diabetes to Alzheimer’s and other forms of dementia. Studies suggest that having diabetes may increase the risk for developing serious memory and thinking problems, including dementia. And some research has suggested that careful control of diabetes can help to prevent memory decline. In addition, low levels of blood sugar in the brain can trigger thinking problems and damage nerves.
For this study, researchers at the University of California, San Francisco, studied 783 elderly men and women (average age 74) with diabetes. During the 12-year course of the study, about 8 percent had at least one episode of hypoglycemia, and 19 percent had developed Alzheimer’s or another form of dementia.
The researchers found that those who’d experience a serious episode of low blood sugar had twice the risk of developing dementia (34 percent vs. 17 percent) than those who never had a hypoglycemic episode. The increased risk persisted even after the researchers controlled for such factors as age, educational level and other medical problems.
Similarly, study participants with dementia were twice as likely to experience a severe hypoglycemic episode than those who were dementia-free (14 percent vs. 6 percent). It may be that those with dementia and diabetes do not control their diabetes as well, so are more prone to getting to the point where their blood sugar levels become dangerously low.
“Hypoglycemia commonly occurs in patients with diabetes mellitus and may negatively influence cognitive performance. Cognitive impairment in turn can compromise diabetes management and lead to hypoglycemia,” the authors wrote.
The authors of an editorial accompanying the study note that hypoglycemia is a common complication of diabetes treatment with insulin and other drugs that act to lower blood sugar levels. The condition is particularly likely in the elderly, who may have a hard time processing drugs. Common symptoms of hypoglycemia include fainting and, in severe cases, loss of consciousness and seizures.
They call for greater awareness of the potential for dangerously low blood sugar in those being treated for diabetes. Those with diabetes should never forgo their diabetes medications. But it’s also critical for anyone being treated for diabetes, with or without dementia, to keep blood sugar levels in a healthy range – neither too high nor too low.
"Individuals with dementia or even those with milder forms of cognitive impairment may be less able to effectively manage complex treatment regimens for diabetes and less able to recognize the symptoms of hypoglycemia and respond appropriately, increasing their risk of severe hypoglycemia," Dr. Yaffe said. "Physicians should take cognitive function into account in managing diabetes in elderly individuals."
Certain medications known to carry a higher risk for hypoglycemia, including some types of insulin and sulfonylurea drugs, may be inappropriate for older adults with dementia or who are at risk for cognitive impairment, she said.
Sources: Kristine Yaffe, MD, Cherie M. Falvey, MPH, Tamara B. Harris MD, et al: “Association Between Hypoglycemia nad Dementia in a Biracial Cohort of Older Adults With Diabetes Mellitus.” JAMA Internal Medicine. Published online June 10, 2013. doi:10.1001/jamainternmed.2013.6189.
Kasia J. Lipska, M.D., M.H.S., Victor M. Montori, M.D.: “Glucose Control in Older Adults With Diabetes Mellitus—More Harm Than Good?” JAMA Internal Medicine, published online June 10, 2013.