Medication used to treat type 2 diabetes has been linked to a 35% lower risk of dementia in a new study.

Experts said the idea of repurposing existing drugs to treat diseases that cause dementia “is one that has huge potential”, although researchers stressed trials are needed to confirm their findings.

The study by Korean academics analysed data from 110,885 type 2 diabetics aged between 40 and 69 on the Korea National Health Insurance Service.

The patients were either taking sodium-glucose cotransporter-2 (SGLT-2) inhibitors, which work by reducing the amount of glucose the kidneys reabsorb, allowing it to pass out of the body in urine, or dipeptidyl peptidase 4 (DPP-4) inhibitors, also known as gliptins, which work by blocking an enzyme that helps the body increase insulin levels after eating.

During a follow-up period, 1,172 people were newly diagnosed with dementia.

The study found SGLT-2 inhibitors were linked to a 35% lower risk of dementia compared with DPP-4 inhibitors.

Researchers said: “This association was similarly observed for Alzheimer’s disease and vascular dementia and was also consistent across subgroups.

“We observed a greater association with treatment duration longer than two years.

“These findings underscore the need for future randomised controlled trials.”

Dr Jacqui Hanley, head of research at Alzheimer’s Research UK, also called for the findings – published in The BMJ – to be confirmed in “robust clinical trials”.

“It will also be important to investigate the mechanisms behind this apparent effect, as this could give researchers clues for other treatment approaches,” she said.

“It is encouraging to see large studies exploring whether drugs that have already been licensed could be repurposed as dementia treatments.

“Since these drugs have already been shown to be safe for use in people, this could potentially speed up the process of testing them in clinical trials against dementia, as well as making it significantly cheaper.

“More broadly, the idea of repurposing existing drugs to treat the diseases that cause dementia is one that has huge potential.

“At Alzheimer’s Research UK, we know that roughly a third of drugs in clinical trials for Alzheimer’s disease are already used for other conditions.

“If we are to cure dementia, clinicians will need a toolkit of treatments which tackle different aspects of the disease and can be used in combination.

“Research into repurposing drugs may help us do just that.”

Professor William Whiteley, associate director of the British Heart Foundation Data Science Centre, clinical lead at the Scottish Stroke Research Network, and professor of neurology and epidemiology at the University of Edinburgh, warned the findings could be down to a “quirk of the study design”.

“People with diabetes have a higher risk of dementia, so finding medicines to reduce this risk is important,” he said.

“Unfortunately, one can never be sure about the effects of a medicine by looking at health record data.

“If this study were true, then SGLT-2 inhibitors would almost halve the risk of some types of dementia, which is much larger than the effect of medicines to reduce dementia progression, or medicines to prevent heart attack and stroke.

“Instead, a quirk of the study design has probably given this result.”