Cognitive functioning abilities drop as average blood sugar levels rise in
people with type 2 diabetes, according to a new study conducted by researchers
at Wake Forest University Baptist Medical Center.
The ongoing "Memory in Diabetes," or MIND, study, which is a sub-study of the
"Action to Control Cardiovascular Risk in Diabetes Trial," or ACCORD,
study, found a statistically significant inverse relationship between A1C
levels, or average blood glucose levels over a period of two months to three
months, and subjects' scores on four cognitive tests. No association, however,
was found between daily blood glucose levels —measured by the fasting plasma
glucose test — and test scores.
For the study, researchers at 52 of the 77 ACCORD sites throughout the United
States and Canada administered a 30-minute battery of cognitive tests to nearly
3,000 people ages 55 and older.
"The tests used in the study measured several aspects of memory function,"
said Jeff Williamson, MD, MHS, principal investigator for the study at the Wake
Forest clinical site. "For example, we tested one's ability to switch back and
forth between memory tasks or to 'multitask,' an important skill for people
needing to manage their diabetes."
The results showed that a 1 percent increase in A1C corresponded to slightly
lower scores on tests of psychomotor speed, global cognitive function, memory
and multiple task management.
"One of the little known complications of type 2 diabetes is memory decline
leading to dementia, particularly Alzheimer's dementia," said Williamson, a
professor of internal medicine, director of gerontology and geriatrics research
and director of the Roena Kulynych Center for Memory and Cognition Research at
Wake Forest Baptist. "This study adds to the growing evidence that poorer blood
glucose control is strongly associated with poorer memory function and that
these associations can be detected well before a person develops severe memory
loss."
Diabetes is a risk factor for mild cognitive impairment, vascular dementia
and Alzheimer's disease. Previous studies have shown that people with diabetes
are 1.5 times more likely to experience cognitive decline and develop dementia
than people without diabetes. The ACCORD-MIND study supports the idea that the
brain's chronic exposure to elevated blood glucose levels may be part of the
explanation for this phenomenon.
Alternatively, people with impaired cognitive ability have higher A1Cs
because they are less compliant in taking medications and controlling their
diabetes. The ongoing ACCORD-MIND study, which is overseen by Williamson and a
team of Wake Forest Baptist researchers, will test the hypothesis that lowering
A1C could result in improved cognitive function.
Meanwhile, "people with type 2 diabetes and their health care providers need
to be careful in situations where there is education and teaching about diabetes
care, as patients may need a little more time to absorb and process
information," Williamson said. "Patients also need to be open to having a family
member periodically making sure they are keeping track of managing their
diabetes through monitoring, diet, exercise and medication."
(Story courtesy Wake Forest University Baptist Medical Center, Feb. 11,
2009. This story does not contain original reporting by The Nation’s Health
staff.)
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