A poor sense of smell may predict premature death, even among healthy individuals, new research suggests.
Older adults who had trouble recognising or telling apart common odours were almost 50% more likely to die over a 10-year period than individuals with sensitive noses, the study showed.
Impaired smell sense may flag up deteriorating health before it is recognised by doctors, scientists believe. For this reason, smell tests could one day become routine in GP surgeries.
Dr Honglei Chen from Michigan State University said poor sense of smell becomes more common as people age, and there’s a link to a higher risk for death. “Our study is the first to look at the potential reasons why it predicts a higher mortality.”
Dr Chen’s team analysed data from almost 2 300 men and women who took part in a major US investigation called the Aging’s Health ABC Study.
Part of the study involved completing a smell test of 12 common odours. The participants, aged between 71 and 82, were then classified as having a good, moderate or poor sense of smell. Compared to those having a good smell sense, people in the “poor” category were 46% more likely to die after 10 years and 30% after 13 years.
The association was almost unaffected by gender, race and lifestyle factors. But to the surprise of the scientists, poor sense of smell even predicted earlier death in healthier participants. The findings are published in the journal Annals of Internal Medicine.
‘Broader implications’
While poor sense of smell is an early sign of Parkinson’s disease and dementia, and linked to weight loss, this only explained 28% of the increased risk of death. Dr Chen said: “We don’t have a reason for more than 70% of the increased risk. We need to find out what happened to these individuals. It tells us that in older adults, 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 at some point.”
Robert Howard, professor of old age psychiatry at University College London, said: “The study showed that the risk of dying in the next 10 years was increased by about a half in people with impaired sense of smell and that only some of this risk could be explained by the development of Parkinson’s or Alzheimer’s or by weight loss.
“Most of the increased mortality risk could not be explained by associations with specific illnesses such as cancer or cardiovascular disorders. 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 their doctors.”