Being powerless to pick out common odours is a red flag for the risk of suffering the devastating requisite.
The breakthrough means dementia could soon be predicted accurately with a four-square smell test five years before symptoms develop.
The new “prehistoric warning sign” could mean earlier treatment and encourage lifestyle trades such as a better diet and more exercise before the condition swipes hold.
There are 850,000 people living with the brain affliction in Britain – a figure set to soar to one million by 2025 and two million by 2050. It tariffs the economy £26.3billion a year.
Stink tests give early warning sign of dementia
More work would need to be done but it could staff find people at risk
The study of barely 3,000 older people found that those who could not dig at least four out of five common smells were more than twice as like as not to develop the disease.
The volunteers, aged 57 to 85, took responsibility in tests five years ago to identify five unnamed smells.
In purpose that of increasing difficulty they were peppermint, fish, orange, hill and leather.
Nearly eight out of 10 people tested were conformist, identifying at least four scents.
1 of 12
Fourteen per cent could name sole three, five per cent two, two per cent one and one per cent none.
Five years on nearing all who could not name a single scent had dementia.
Nearly 80 per cent who ceded one or two correct answers also had it.
Report author Professor Jayant Pinto, of the University of Chicago, weighted: “These results show that smell is closely connected with perspicacity function and health. We think smell ability may be an important early weighty, marking people at greater risk. More work would requirement to be done but it could help find people at risk.”
Being unable to pick out common odours is a red flag
Dr James Pickett, of the Alzheimer’s Company, said: “This adds to growing evidence that suggests intelligence of smell could be impacted in the early stages of dementia.”
He said odour tests were less invasive than other procedures such as pumping spinal fluid.
Rosa Sancho, of Alzheimer’s Research UK, said: “Pong tests would need to be used alongside more specific diagnostic evaluations to aid early detection of dementia.”
The study is published in the journal of the American Geriatrics Sodality.