A bad sense of smell predicts early death but we don’t know why

By | April 30, 2019
Inability to distinguish odours could be a sign of ill health

Inability to distinguish odours could be a sign of ill health

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A poor sense of smell in older adults is linked to a nearly 50 per cent increase in the likelihood of dying in the next 10 years, but the reasons for this aren’t fully clear.

The relationship between olfaction and health is often overlooked, however a growing body of research suggests a poor sense of smell can foreshadow the onset of Parkinson’s disease and even premature mortality.

To investigate further, Honglei Chen of Michigan State University and his colleagues analysed data from more than 2000 people aged 71 to 82.

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Each person did a type of test that assesses how good someone is at identifying 12 common odours, such as cinnamon, lemon, gasoline and smoke. The team then tracked the survival of the participants for 13 years afterwards.

Compared with those who scored highly on the smell test, those who correctly identified no more than eight odours were 46 per cent more likely to have died 10 years later, and 30 per cent more likely to have died by the end of the 13 years.

Analysing the data, the team found that a poorer sense of smell wasn’t linked to deaths from cancer or respiratory illnesses, but was strongly associated with deaths from Parkinson’s disease and dementia. There was a modest link with deaths from cardiovascular disease.

It had been thought that a worsening sense of smell might lessen a person’s interest in food, leading to weight loss and worsening health. But the team found that weight loss, dementia and Parkinson’s disease together only explained around 30 per cent of the higher mortality associated with a poor sense of smell.

Unfortunately, people are often unaware of their sense of smell degrading and it’s rarely tested by doctors.

“In the future, as these potential health implications are unveiled, it may not be a bad idea to include a sense of smell test as part of your [doctor’s] visit,” says Chen.

Journal reference: Annals of Internal Medicine, DOI: 10.7326/M18-0775

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