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Impaired sense of smell linked to dementia risk

Decreased ability to identify smells could be an early indicator of cognitive decline and dementia. 

Decreased ability to identify smells could be an early indicator of cognitive decline and dementia, say researchers from Columbia University Medical Center in the United States. 

They carried out two studies looking at the changes in sense of smell and compared this to two established characteristics of dementia – the amount of amyloid protein in the brain and the size of the brain area that is important for memory. 

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The first study used the University of Pennsylvania Smell Identification Test (UPSIT) to test sense of smell in 397 older people without dementia. Brains scans were carried out to look for thinning of the entorhinal cortex, an area of the brain important for memory that is affected early in Alzheimer’s disease. 

During the four-year follow-up period, 50 participants developed dementia. Impaired sense of smell and thinning of the entorhinal cortex were both significantly associated with transition to dementia, with sense of smell also predicting cognitive decline. 

In a second study looking at how well a declining sense of smell can predict cognitive decline, the researchers used the UPSIT score to rate sense of smell in 84 people, and brain imaging or spinal fluid analysis to determine the level of brain amyloid protein. 

At two or four-year follow-up, 67% of participants showed signs of memory decline. The researchers said the amount of brain amyloid present predicted memory decline, but not odour identification. However, those with an impaired sense of smell were three times more likely to have memory problems. 


The study results were presented at the Alzheimer’s Association International Conference in Toronto, Canada, on 26 July. 

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