Cognitive decline is worse in diabetes

Having diabetes, especially if it is inadequately controlled, is associated with worse cognitive function, research has shown. The study, published online first in Archives of Neurology, also found that well-functioning older people with diabetes were more likely to experience worse cognitive decline than those without diabetes.

Researchers in California assessed the cognitive function of 3069 people aged 70-79 years, nearly a quarter of whom already had diabetes at baseline. About a further 5% were diagnosed with diabetes during the 10-year follow up.

Participants’ cognitive function was reassessed at their 3-, 5-, 8- and 10-year follow-up visits.

People with diabetes at baseline already had lower cognitive test scores than people who did not have diabetes. In addition, among people with diabetes at baseline there was a significant association between higher glycosylated haemoglobin (HbA1c) levels and poorer cognitive function, even after adjustment for age, sex, race and educational level.

People who already had diabetes showed significantly worse cognitive decline over the follow-up period than those without diabetes.

The authors also reported that people who developed diabetes during their study showed a ‘trend towards intermediate cognitive decline’. They said: “This suggests that delaying or preventing the onset of DM [diabetes mellitus] may prove beneficial for maintaining cognitive function in older adults, especially considering that a longer duration of DM has been linked to worse cognitive function, including mild cognitive impairment.”

They concluded: “This study supports the hypothesis that older adults with DM have reduced cognitive function and that poor glycaemic 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.”