London - A poor sense of smell could be an early warning sign of dementia, research suggests.
A study found elderly men and women who performed badly in smell tests were more likely to show signs of memory loss over the next three-and-a-half years.
And those who had the weakest sense of smell were at the highest risk of developing Alzheimer’s.
The findings raise the prospect of a simple sniff test being used to identify patients at greater risk of dementia in later life.
US scientists at the Mayo Clinic research centre in Minnesota tested 1 430 men and women with an average age of 79. They used a standardised smell test which measured how accurately the participants could identify 12 scents – six of foods including banana and cinnamon, and six non-foods such as petrol, soap and roses.
The participants, who were all assessed as having no dementia symptoms at the beginning of the study, were then tracked over the next three-and-a-half years.
During that time, 250 developed signs of mild cognitive impairment – often the first stage of dementia. Of those, 64 were later diagnosed with dementia, 54 of whom had the Alzheimer’s form of the disease.
The scientists, whose work is published in the journal JAMA Neurology, did not examine the participants’ brains so could not prove a link. But they suspect that deterioration in the part of the brain that controls smell could coincide with deterioration in the area that controls memory. The experts warned that there are many reasons someone may start to lose their sense of smell in later life – and that it might not necessarily be linked to dementia.
But they added that in the future, sniff tests may be combined with other diagnostic tools to give an early warning of dementia years before the main symptoms appear.
They wrote: “Clinical implications of our findings are that odour identification tests may have use for early detection of persons at risk.”
British experts welcomed the breakthrough – but said more research is needed. Dr Doug Brown, of the Alzheimer’s Society, said: “This study adds to the growing evidence that a deteriorating sense of smell could be an early indicator of Alzheimer’s.
“If used in combination with other tests it may help researchers to identify which of those already experiencing memory problems are at a greater risk of dementia.”
However, he added: “It is really important to note that most people experience some sensory loss as they age, so those with a decreased sense of smell shouldn’t be immediately worried that it means they will develop Alzheimer’s disease.”
Daily Mail