Loss of smell linked to cognitive decline and dementia in older people

Published 13 July 2014

A decreased ability to identify odours could be an early indicator of cognitive decline and Alzheimer's disease, according to research presented today (13 July 2014).

The findings were presented at Alzheimer's Association International Conference in Copenhagen. Two studies presented suggested a significant correlation between poor performance on a smell test and either memory problems or the transition from mild memory impairment to Alzheimer's.

Researchers from Harvard Medical School administered a 40 item smell test known as UPSIT to 215 clinically healthy older people alongside a battery of other cognitive tests. Those subjects with worse smell identification had smaller brain volumes in two areas linked to memory – the entorhinal cortex and the hippocampus and were more likely to have a poor memory.

In a separate study at Columbia University, researchers investigated a sample of 1,037 people without dementia with an average age of 80.7. Over the course of four years, participants were assessed three times. Lower odour identification scores on the UPSIT test were found to be significantly associated with increased incidence of dementia. For each point lower scored on the smell test, the risk of developing dementia increased 10 per cent. In addition, lower UPSIT scores at the start were significantly associated with cognitive decline in those who started the study without memory problems.

Dr Doug Brown, Director of Research and Development at Alzheimer's Society said of the findings:

'Most people experience some sensory loss as they age, so people with a poor sense of smell shouldn't be immediately worried about dementia. There are more than sixty medical conditions that can affect your ability to smell odours including some medications. These studies do add to the growing evidence that changes in the sense of smell could be an early indicator of Alzheimer's disease, but we need larger studies to test how reliable smell tests could be in the clinic.

'Finding a way to detect dementia early is vital for future research and to help people manage their condition better. Studies like this are a step in the right direction, but with six times more spent on cancer than dementia we need to see significantly more investment to enable a step change in research to help turn discoveries like this into meaningful clinical tools.'

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