High blood sugar levels, a precursor of diabetes, were tied to an increased risk of dementia in older men and women. The findings are worrisome since so many people have diabetes, obesity or high blood sugar levels, all of which are inter-related and have been linked to an increased risk of brain problems, including Alzheimer’s and other forms of dementia.
Diabetes has been linked to dementia in earlier studies. This study is among the first to show that high blood sugar levels, well below the range considered to be a sign of diabetes, also appear to be bad for memory and thinking skills. The findings appeared in the New England Journal of Medicine.
“The most interesting finding was that every incrementally higher glucose level was associated with a higher risk of dementia in people who did not have diabetes," said the lead author, Dr. Paul K. Crane, of the University of Washington School of Medicine and the Group Health Research Institute.
More than 25 million Americans have diabetes. Far more have high blood sugar levels, which set the stage for full-blown diabetes.
For the study, part of a larger study called the Adult Changes in Thought (ACT), researchers at the University of Washington measured blood sugar, or glucose, levels in more than 2,067 men and women who were free of dementia. Their mean age was 76. More than 10 percent, or 232, had diabetes.
Over the 7-year course of the study, participants were given regular tests of blood, as well as memory tests to screen for Alzheimer’s and other forms of dementia. During that time, dementia developed in 524 of the participants, 74 of whom had diabetes.
Among those who did not have diabetes, higher blood sugar readings -- above 115 milligrams per deciliter of blood -- were tied to an increased risk of dementia. In those with diabetes, high blood sugar was also tied to increased dementia risk. The higher the blood sugar readings, the greater the risk.
"One major strength of this research is that it is based on the ACT study, where we follow people for many years as they lead their lives," said senior author Dr. Eric B. Larson. “This gave us an average of 17 blood sugar measurements per person: very rich data."
The findings provide robust new evidence that high blood sugar can have damaging effects on the aging brain. One reason for this, the authors say, is that uncontrolled blood sugar can damage blood vessels throughout the body, including in the brain. Poor blood flow to the brain is a recognized cause of dementia and may worsen the memory problems in someone with Alzheimer’s.
It is unclear whether treating high blood sugar would prevent the onset of dementia; the study did not look at that. But regular exercise, like walking, swimming and ballroom dancing, is known to help keep blood sugar in a healthy range, keep weight down and stave off diabetes. Regular exercise is also tied to a lower Alzheimer’s risk.
Source: Paul K. Crane, M.D., M.P.H., Rod Walker, M.S., Rebecca A. Hubbard, Ph.D., et al: Glucose Levels and Risk of Dementia. New England Journal of Medicine, Volume 369, No. 6, August 8, 2013