A study featured Online First in Archives of Neurology reveals that Diabetes mellitus (DM) and poor glucose control in older, well-functioning adults with no dementia are linked to reduced cognitive function and higher cognitive decline.

Background information in the study states that earlier studies indicated a link between DM and a higher risk of cognitive impairment as well as dementia and Alzheimer’s. However, this association still creates controversy, as the knowledge about incident DM in late life and cognitive function over time still remains inadequate.

To find out more, Kristine Yaffe, M.D., from San Francisco’s University of California and the San Francisco VA Medical Center and her team decided to assess 3,069 patients, who had an average age of 74.2 years. 42% of all participants were black and 52% were female. At the start of the study, the participants were asked to complete the Modified Mini-Mental State Examination (3MS) and Digit Symbol Substitution Test (DSST), which were repeated at selected intervals over a period of 10 years.

The findings showed that 717 participants or 23.4% had prevalent DM at the start of the study, whilst 2,352 or 76.6% had no DM. 159 participants developed DM during follow-up. Those with DM at the study start had lower 3MS and DSST test scores compared with those with no DM. The findings demonstrate a similar pattern of decline at 9-years whereby participants with DM demonstrated a substantial decline in both the 3MS test and the DSST test compared with those who had no DM.

The researchers also noted a link between elevated hemoglobin A1c (HbA1c) levels and lower 3MS and DSST scores in those participants with DM at the start of the study. After the team adjusted the finding for variables, including age, sex, race and education, the scores were still substantially lower in those with medium, i.e. 7-8% and high, i.e. ≥ 8% HbA1c levels in the 3MS test, yet with regard to the DSST test, they were no longer significant.

The researchers conclude:

“This study supports the hypothesis that older adults with DM have reduced cognitive function and that poor glycemic control may contribute to this association. Future studies should determine if early diagnosis and treatment of DM lessen the risk of developing cognitive impairment and if maintaining optimal glucose control helps mitigate the effect of DM on cognition.”

Written By Petra Rattue