Cheap diabetes drugs already taken by millions of people may slow down the progression of Alzheimer’s, helping patients to live without severe symptoms for longer, a new study suggests.

Researchers in the US examined the brains of 63 people with dementia, around half of whom were also diabetic and were taking drugs like metformin or the hormone insulin.

Tests on blood vessels and brain tissue found that half of the biological markers used to diagnose Alzheimer’s were reduced in the diabetics.

The researchers believe the drugs have a protective effect on the vascular system of the brain and have called for trials to test whether they could slow down the disease.

Diabetes drugs cost just a few pence per pill and have already passed safety trials, so clinical studies could be relatively quick.

The new research also suggests that other drugs which target the brain's capillary system could have beneficial effects in Alzheimer's patients.

"The results of this study are important because they give us new insights for the treatment of Alzheimer's disease," said senior author Dr Vahram Haroutunian, Professor of Psychiatry and Neuroscience at the Icahn School of Medicine at Mount Sinai.

"Most modern Alzheimer's treatments target amyloid plaques and haven't succeeded in effectively treating the disease.