If you can’t smell onion, better see your doctor

Losing the ability to smell strong odours such as onions, petrol or lemons in later life could be a warning sign that death is approaching, a study has found. Researchers tested the smelling ability of 2,300 people aged between 71 and 82, then followed them for more than 10 years. During that period poor smellers were found to be far more likely to have died than those with a good sense of smell.

LOSING the ability to smell strong odours such as onions, petrol or lemons in later life could be a warning sign that death is approaching, a study has found.

Researchers tested the smelling ability of 2,300 people aged between 71 and 82, then followed them up for more than 10 years.

During that period, around half died. For those who struggled to smell, the risk of dying within 10 years rose by 46 per cent, meaning around threequarters of the poor smellers were dead within a decade.

Losing the ability to smell often goes hand in hand with diseases such as Parkinson’s and Alzheimer’s, as the neurodegenerative conditions kill off olfactory nerves needed to sense odours.

However, the study found that such diseases accounted for fewer than onethird of cases, and seven in 10 of the bad smellers had appeared healthy before their deaths. “We don’t have a reason for the increased risk. We need to find out what happened to these individuals,” said Honglei Chen, an epidemiologist at Michigan State University.

“It tells us that in older adults an impaired sense of smell has broader implications of health beyond what we have already known. Incorporating a sense-of-smell screening in routine doctor visits might be a good idea.”

Those involved in the study were asked to take part in the Brief Smell Identification Test (BSIT), in which 12 odours are released by scratching scent strips with a pencil. The smells include rose, soap, banana, chocolate, smoke and turpentine, and were chosen because of their distinctiveness and familiarity in most cultures. Commenting on the study, experts said it was important for older people to let their doctor know if their sense of smell began to diminish, as it could herald unseen problems.

Robert Howard, professor of old age psychiatry at University College London, said: “We have known for many years that loss of sense of smell in later life may precede other symptoms of neurodegenerative disorders by many years. The study showed that the risk of dying in the next 10 years was increased by about a half in people with an impaired sense of smell, and that only some of this risk could be explained by the development of Parkinson’s or Alzheimer’s.

“This raises the interesting possibility that loss of smell may be a marker of generalised ageing and should be taken seriously by older people and doctors.”

A previous study by the University of Florida found it may be possible to diagnose Alzheimer’s by testing how close a person needed to be to a peanut to smell it. Patients who needed the nut to be at least 2.3 inches closer to the left nostril than the right before they could detect its odour were all diagnosed with Alzheimer’s.

Dr Sara Imarisio, head of research at Alzheimer’s Research UK, said: “Previous research has suggested that changes in sense of smell could be an early indicator that diseases like Alzheimer’s are under way in the brain.

“While scientists are exploring the potential of smell tests to help detect diseases like Alzheimer’s at an early stage, these need to be refined and evaluated in clinical trials before they could be used to support a diagnosis.”

The research was published in the journal Annals of Internal Medicine.