SATURDAY, June 5, 2004 (HealthDayNews) -- New research shows that people with diabetes who reduced their blood sugar levels experienced improvements in working memory.
While previous studies have shown that managing blood sugar can have salutary effects on other complications of diabetes, such as kidney function, blindness and retinopathy, this latest study is the first to extend the effect to cognitive function, an area which has traditionally received less attention.
"The more they lowered their blood glucose levels, the better," said study co-author Christopher Ryan, a professor of psychiatry at the University of Pittsburgh School of Medicine. "Cognitive impairment may be reversible and preventable."
The findings were presented June 5 at the American Diabetes Association's annual meeting in Orlando, Fla.
"Research has shown that people with type 2 diabetes are up to twice as likely as the general population to experience cognitive decline," Dr. Richard Nesto, chairman of cardiovascular medicine at the Lahey Clinic in Massachusetts, said at a teleconference this week to announce the results. "There are 17 million people with type 2 diabetes in the U.S. today, and even mild cognitive impairment can negatively impact learning and memory and may impact ability to perform routine tasks."
Common cognitive difficulties experienced by people with type 2 diabetes include difficulty learning new information and remembering that information, said study co-author Dr. Mark Strachan, of Western General Hospital in Edinburgh, Scotland.
Of particular concern to doctors is how these mental difficulties may impact management of the blood sugar disease.
"We have to keep in mind that the presence of even mild memory problems can affect quality of life in a variety of ways, including the ability to follow complex medical regimens, remembering whether or not you took your medication or tested your blood sugar," Ryan said. "Mild memory problems can have a major impact on patients' adherence with medical management."
This study, the largest ever to look at the effect of glycemic control on cognitive function in people with type 2 diabetes, set out to determine if there was a relationship between the two factors.
To that end, they recruited 141 people who, other than having been diagnosed with diabetes, were relatively healthy. The average age of the participants was 60.
All of the participants took the drug metformin and were then randomized to take either Avandia or glyburide. Fasting plasma glucose was measured at the beginning of the 24-week trial and all individuals took a battery of psychological tests to ascertain cognitive function. Three categories of function were assessed: learning ability, cognitive efficiency and working memory
"The main result of the study was improving glycemic control has no effect on learning ability or cognitive efficiency, but we found that in both arms of study there was a significant improvement in working memory across the 24 weeks. And in one of the major tests that made up the working memory domain, we saw that there was a 30 percent improvement in errors that patients made across the study," Strachan said.
In both groups, working memory improvements correlated with improved control of blood sugar levels. "Those subjects that had the biggest improvement in glycemic control had the biggest improvement in working memory," Strachan said. Avandia, however, had fewer side effects.
It's not clear why working memory improved while other areas did not. It's possible that another set of patients not in such good health would show more widespread declines.
Although the findings need to be replicated and verified, they do seem to provide yet more evidence for controlling blood sugar.
"Our study reinforces the results of previous studies," Strachan said. "We know that good glycemic control and strict management of other diabetes-related parameters is good for your long-term health. This is one further reason why we should be striving to get good glycemic control. It's not doing any harm to get sugar under control better."
More information
The American Diabetes Association has more on type 2 diabetes.
