Elderly adults without dementia who have diabetes and struggle with maintaining glycemic control are at risk for accelerated cognitive decline, based on research from a prospective cohort study.
According to the CDC, approximately 27% (10.9 million) of adults aged 65 years and older have diabetes.
“Many studies report a link between diabetes mellitus and decreased cognitive function, with a stronger association found in older (>60 years) adults compared with younger groups,” researchers wrote in a study published in the Archives of Neurology. “However, most studies investigating diabetes mellitus and cognitive function have either been case-control or prospective studies that focused on the prevalent diabetes mellitus determined only at baseline.”
Kristine Yaffe, MD, of the University of California, and colleagues aimed to evaluate this association by conducting a study beginning in 1997 that included 3,075 community-dwelling white and black adults living in Memphis, Tenn., or Pittsburgh. The mean age of the participants at baseline was 74.2 years.
Patients were administered the modified mini-mental state examination (3MS) during follow-up visits at years 1, 3, 5, 8 and 10. A digit symbol substitution test (DSST) was administered at baseline and selected intervals over 10 years. Additionally, HbA1c levels were measured at years 1 (baseline), 4, 6 and 10 from fasting whole blood.
“Decline scores on the 3MS among those with incident diabetes mellitus were also similar to those with prevalent diabetes mellitus. In addition, participants with diabetes mellitus who had a higher HbA1c level performed more poorly on cognitive tests, suggesting that glucose control is related to cognitive function,” researchers wrote.
Of the 3,075 patients in the study, 717 (23.4%) had prevalent diabetes, which was associated with black males with less high school education, as well as a history of myocardial infarction or hypertension, and a higher BMI. Moreover, 159 (5.2%) patients developed diabetes during follow-up, researchers said.
At baseline, patients with prevalent diabetes had lower unadjusted 3MS and DSST scores compared with patients without diabetes (P=.001). Once adjusted, patients with prevalent diabetes compared with those without had a slightly lower mean 3MS baseline score (P=.01) and DSST score (P=.03).
After 9 years, patients with prevalent diabetes had a significant decline on both the 3MS (P=.008) and the DSST (P=.001), compared with patients without diabetes, researchers wrote. The decline was still substantially evident after adjustments for age, race, sex and education (P=.001).
HbA1c levels among patients with diabetes were associated with lower average cognitive scores on the 3MS (P=.003) and DSST (P=.04), even after multivariate adjustment, they said.
Further studies were suggested by the researchers to determine whether early diagnosis and treatment of diabetes will decrease the risk for developing cognitive decline.
- Dr. Yaffe reports serving on data safety monitoring boards for Medivation, the NIH and Pfizer; and has received research support from NIH, the Department of Defense, American Health Assistance Foundation, Anonymous Foundation, and the Alzheimer’s Association. Other researchers report financial ties with Amgen, GlaxoSmithKline, Merck Serono, Novartis and the NIH. Eleanor M. Simonsick, PhD, serves as an associate editor for the Journal of Gerontology Medical Sciences.