Older people with type 2 diabetes may struggle more with verbal memory than their peers without the disease, a recent study suggests.
Researchers followed 705 older adults without dementia for an average of 4.6 years. At the start, participants were between 55 and 90 years old, with an average age around 70, and 348 of them had diabetes.
In people with diabetes, verbal fluency declined slightly over the course of the study, while it improved slightly in participants without diabetes, researchers report in Diabetologia.
Diabetes develops when the body can't properly use insulin to convert blood sugar into energy and the condition is associated with obesity and aging. While diabetes has long been linked to cognitive decline and dementia, research to date hasn't offered a clear reason for this connection.
Three times during the study, participants had brain scans to look for any signs of atrophy - tissue shrinkage - and they took cognitive tests involving verbal skills.
Although people with diabetes already had more brain atrophy at the start, there was no difference between those with and without diabetes in the rate of brain shrinkage during the study. Atrophy also didn't appear to explain the link between diabetes and cognitive decline.
Still, the results suggest that brain changes associated with diabetes may begin earlier than previously thought, perhaps in middle age, said lead author Michele Callisaya of the University of Tasmania in Hobart, Australia.
For patients, this means it would be a mistake to put off thinking about brain health until they're older or experiencing symptoms of cognitive decline, Callisaya said by email.
"Recommendations for good brain health include physical activity, following a healthy diet, maintaining a healthy weight, checking blood pressure and cholesterol, mentally challenging the brain and enjoying social activities," Callisaya said.
The diabetics in the study were a bit younger, 68 years old on average, compared with an average of 72 for the participants without diabetes.
Researchers accounted for age, sex, education and risk factors like current or former smoking, obesity and elevated blood pressure or cholesterol.
One limitation of the study is that the diabetics had relatively well-controlled blood sugar, and it's possible that the connection between diabetes and changes in the brain might be more apparent in patients with higher blood sugar, the study authors note.
"There isn't evidence that keeping blood (sugar) under control directly improves cognition or lessens cognitive decline," said Dr. Rebecca Gottesman of Johns Hopkins University in Baltimore, Maryland. "But it is likely that long-term control of blood sugar has benefits for the brain," Gottesman, who wasn't involved in the study, said by email.
Another limitation is that the study may have been too brief to detect meaningful differences in cognition and brain volume between people with and without diabetes because these changes can happen slowly.
The diabetics might have had reduced brain reserve, or the ability to withstand damage, when they joined the study, said Jill Morris a researcher at the University of Kansas Alzheimer's Disease Center in Fairway.
The good news is there's plenty that people can do to help keep their mind sharp, Morris said in an email.
"Keep your body and mind active," she advised.
"Diet and exercise are key components of brain health and can simultaneously impact blood sugar levels, insulin resistance, and cerebrovascular disease," Morris added. "These factors are linked to important cognitive and brain-related outcomes in a variety of populations, and are especially important in individuals with type 2 diabetes."