Type 2 diabetes drug associated with 35% lower risk of dementia, study finds

A drug used to treat type 2 diabetes is associated with a 35% lower risk of dementia, according to research.

The number of people with dementia globally is expected to nearly triple to 153 million by 2050. The health and social costs linked to dementia already exceed $1tn (£780bn) a year, research shows.

Type 2 diabetes is one of 14 risk factors associated with a greater risk of developing dementia. Other factors are high levels of bad cholesterol, untreated vision loss, hearing impairment, high blood pressure, smoking, obesity and physical inactivity.

Now a large Korean study published in the BMJ has suggested that a medicine used to treat type 2 diabetes, called sodium-glucose cotransporter-2 (SGLT-2) inhibitors, may lower the risk of dementia.

While previous studies have suggested SGLT-2 inhibitors could have a protective effect against dementia for older patients, until now, any protective effect on younger people and specific types of dementia such as Alzheimer’s disease and vascular dementia has been unclear.

The academics analysed data from more than 220,000 type 2 diabetics aged between 40 and 69 on the Korea national health insurance service who did not already have dementia.

Half were taking SGLT-2 inhibitors, which reduce the amount of glucose the kidneys reabsorb, and half were taking another drug called dipeptidyl peptidase 4 (DPP-4) inhibitors, which helps to increase insulin levels after food.

A total of 1,172 participants newly diagnosed with dementia were identified during the study period.

The researchers calculated SGLT-2 inhibitors were associated with a 35% lower risk of dementia compared with DPP-4 inhibitors. They also identified a 39% reduced risk for Alzheimer’s disease and a 52% reduced risk for vascular dementia associated with patients taking SGLT-2 inhibitors.

The authors cautioned that this is an observational study and so could not prove cause and effect, but concluded that repurposing existing drugs to treat diseases that cause dementia “is one that has huge potential”, although further trials were needed to confirm their findings.

Dr Jacqui Hanley, the head of research at Alzheimer’s Research UK, said the data was “promising”, adding: “People affected by dementia urgently need effective treatments, as last week’s news of Alzheimer’s drug lecanemab’s rejection by Nice emphasised.”

Repurposing medication that has already been licensed for treating dementia could speed up the process of testing them in clinical trials, as well as making it significantly cheaper, she said. “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.”

But Prof William Whiteley, the associate director of the British Heart Foundation data science centre, said: “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.”

• This article was amended on 29 August and 16 September 2024. An earlier version accurately reported the research as finding that SGLT-2 inhibitors may lower the risk of dementia, but in two instances incorrectly said it may “prevent” the condition. In addition, an earlier version said that DPP-4 inhibitors block the enzyme that helps increase insulin levels after food. DPP-4 inhibitors help to increase insulin levels after food by blocking the enzyme that destroys hormones called incretins, which help the body to produce insulin.