THURSDAY, May 14, 2020 (HealthDay News) -- Memory and thinking skills are generally worse after a stroke for people with type 2 diabetes compared to people with normal blood sugar levels or prediabetes, new research suggests.
"We found that diabetes, but not prediabetes, is associated with poorer cognitive performance in every aspect of cognition tested," said study lead author Jessica Lo. She's a research associate from the University of New South Wales Sydney's Center for Healthy Brain Aging in Australia. Prediabetes is a condition in which blood sugar levels are higher than normal, but not yet high enough to be considered type 2 diabetes.
People with diabetes are more likely to have strokes than people without the disease. In fact, every two minutes someone with diabetes in the United States is hospitalized due to stroke, according to the Know Diabetes by Heart Initiative, a collaboration of the American Heart Association and American Diabetes Association.
The new research combined data from seven international studies. More than 1,600 people (average age: 66) who had recovered from a stroke were included in the analysis.
They came from six countries. Seventy percent were Asian, 26% were white and 2.6% were black. Nearly all had a stroke caused by a blood clot.
Memory and thinking skills were measured between three and six months after the stroke occurred.
People with diabetes scored much lower on tests that measured: memory; attention; information processing speed; language skills, the ability to copy or draw lines and shapes; mental flexibility, and executive functioning (mental abilities used to focus, plan, recall instructions and multi-task).
People with prediabetes didn't score significantly worse on these tests.
Dr. Jorge Plutzky is a spokesman for the American Heart Association and director of preventive cardiology at Brigham and Women's Hospital in Boston. He was not involved with the research but reviewed the findings.
"This study provides additional evidence that after a stroke, people with diabetes don't do as well," Plutzky said.
And though people with prediabetes didn't have significant memory and thinking problems in this study, he said those with prediabetes should still be concerned about higher-than-normal blood sugar (glucose) levels.
"In terms of cardiovascular events, lots of evidence supports the idea that when you go from normal glucose levels to diabetes, there's a continuum of risk," Plutzky said. "And that continuum includes prediabetes. You don't want to progress to diabetes."
Dr. Minisha Sood, an endocrinologist from Lenox Hill Hospital in New York City, also reviewed the findings and agreed that this study points to a spectrum of risk -- the longer blood sugar levels are high, the bigger the problem.
"While the study findings highlight the importance of avoiding progression to type 2 diabetes if one has prediabetes, it should also be emphasized that achieving prediabetes status should be avoided as well if at all possible," she said.
Lo, Plutzky and Sood all said there are multiple reasons why people with diabetes might have worse memory and thinking skills after a stroke.
Inflammation associated with higher blood sugar may play a role, according to Lo. Plutzky noted that people with diabetes often have small blood vessel disease. After a stroke, the small blood vessels are important for providing blood and oxygen to areas around lost brain tissue. If those vessels are damaged from diabetes, they aren't able to do that as well.
Sood said people with diabetes may not clear certain debris from the brain as effectively as people without higher blood sugar levels do.
Lo said it's important to understand that people with diabetes have poorer outcomes after a stroke, so that their medications and lifestyles can be altered accordingly. Ideally, however, lifestyle changes (eating a healthy diet, losing weight, exercising regularly) should begin before a stroke or other major health event in people with diabetes. Those changes should begin when someone has prediabetes, she said.
"If we could prevent diabetes, we would prevent its adverse life-affecting consequences, such as stroke, dementia, heart disease and kidney failure," Lo added.
The study was published May 14 in the journal Stroke.
Learn more about stroke and diabetes from the American Stroke Association.
SOURCES: Jessica Lo, M.Sc., research associate, University of New South Wales Sydney, Center for Healthy Brain Aging, Australia; Minisha Sood, M.D., endocrinologist, Lenox Hill Hospital, New York City; Jorge Plutzky, M.D., spokesman, American Heart Association, and director of preventive cardiology, Brigham and Women's Hospital, Boston; Stroke, May 14, 2020