Metformin use might have neuroprotective effects in older patients with type 2 diabetes
medwireNews: Results from an observational study suggest that the use of metformin in older patients with type 2 diabetes is associated with a reduced decline in both global cognition and executive function, and a decreased risk for dementia.
The researchers used The Sydney Memory and Ageing Study to collect data from 1037 community-dwelling adults, aged 70–90 years at baseline, four times every 2 years for a period of 6 years. Participants did not have a dementia diagnosis, major neurologic or psychiatric disease, nor progressive malignancy, and their adjusted Mini-Mental State Examination score was less than 24 at baseline. They were classified into three groups: patients with diabetes who were metformin (n=67) and non-metformin (n=56) users, and individuals without diabetes (n=903). The majority (60%) of people using metformin had taken it for more than 5 years.
Using a linear mixed modelling approach, including covariates such as age, sex, education, BMI, and heart disease, the researchers reported no cognitive performance differences at baseline between patients with diabetes who were metformin users and those who were non-metformin users or did not have diabetes.
The average annual rate of decline in global cognition over 6 years – measured by a battery of neuropsychological tests transformed into a composite z score – was similar between patients receiving metformin and those without diabetes, but this rate was signiﬁcantly reduced when metformin users were compared to non-metformin users. Specifically, the average z score decreased from approximately –0.6 to –1.1 among metformin users and from –0.9 to –2.2 among non-metformin users, giving a between-group difference in the rate of change of 0.21.
These findings support the hypothesis “that metformin use is associated with less cognitive decline,” say Katherine Samaras (Garvan Institute of Medical Research, Darlinghurst, New South Wales, Australia) and fellow researchers in Diabetes Care.
In the same way, patients receiving metformin and those without diabetes had a comparable rate of decline in executive function but when metformin users were compared with non-metformin users, a significantly faster rate was observed in the latter group.
The team observed a similar pattern of results when looking at rates of dementia. Over 6 years of observation, there were 91 reported cases of dementia, including 8.2% of the group of patients without diabetes, 14.5% of the non-metformin users and 6.0% of the metformin users. In a Cox regression analysis, metformin users were significantly less likely to develop dementia than non-metformin users, at an adjusted hazard ratio of 0.19.
They also report that patients in the non-metformin group were 3.03 times more likely to develop dementia during follow-up than people without diabetes. No significant differences were observed between patients who were metformin users and patients without diabetes.
The authors conclude “The current study adds to the existing literature supporting that metformin may have neuroprotective effects.”
And they add: “Randomized controlled studies are required to determine whether metformin may have a protective effect against dementia or cognitive decline, both in people with diabetes and, given metformin’s long safety record, older people without diabetes.”
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