Image of a clinician advising a patient about diabetes care.

The odds of developing full dementia among older adults with cognitive impairment triples when diabetes is poorly controlled — but diabetes itself is not a factor in progression, a new study has found.

Researchers followed more than 2,500 individuals aged 60 years and older for 12 years. Although none had a dementia diagnosis at the study’s start, over 700 had cognitive impairment. About 9% of participants had type 2 diabetes, and 1 in 3 had prediabetes, investigators said.

Image of Abigail Dove; Image credit: Karolinska Institute
Abigail Dove; Image credit: Karolinska Institute

Almost 30% of participants developed cognitive impairment over the study period. Using measures of blood glucose (HbA1C) and CRP, an inflammation marker, the researchers found no evidence that type 2 diabetes was linked to the development of cognitive impairment. Nor was it linked to existing cognitive impairment becoming full dementia, reported researcher Abigail Dove, from the Karolinska Institute in Sweden. 

Rather, participants with poorly controlled diabetes, when compared to their peers without diabetes, were twice as likely to develop preclinical dementia. And when these participants already had cognitive impairment, they were three times as likely to progress to a dementia diagnosis, Dove and her colleagues found. 

“What matters is how well-controlled the diabetes is. Since there is currently no cure for dementia, prevention is vital, and here we have evidence that this can be done through the careful control of diabetes,” Dove said.

The results may explain why earlier studies have produced conflicting results about the link between diabetes and dementia. Few of them have factored in diabetes control, she said.

According to the treatment guidelines for older adults, HbA1C of over 7.5% is considered poorly controlled diabetes, the researchers noted.

The study was published in the journal Alzheimer’s & Dementia.