A diminishing sense of smell could be a sign of declining health and potential frailty, a new study has warned.
Doctors at Johns Hopkins University in the US compared the olfactory abilities of more than 1,000 elderly people with a questionnaire and assessment on their health which produced a score for frailty.
They found that those who were the most frail and had the worst standards of overall physical health also had the worst sense of smell.
The finding suggests that smell loss could be a useful indicator of overall health in older people and the team have called for it to be included in future health check-ups.
Adding smell tests to routine screenings could help identify someone's risk of unhealthy ageing, and act as a tipoff to whether additional tests are needed, they argue.
“We already do tests to assess how well we can see or hear, and it's just as easy to conduct a simple smell test that takes only minutes, which could potentially be used as a valuable tool to assess the risk of frailty or unhealthy ageing,” said Dr Nicholas Rowan, associate professor of head and neck surgery from John Hopkins University, and study author.
"For example, if someone flunks a smell test then maybe this patient needs to improve their nutrition or undergo a more detailed neurological or medical workup."
The study builds on previous research that shows a drop in one's ability to smell is a common early sign of cognitive decline.
However, the findings suggest that the connection to frailty is likely not just in the brain but also a genuine drop in smelling ability.
The study, published in the Journal of Gerontology, tested participant's capabilities to detect an odour's presence and name a scent.
These measures are called olfactory sensitivity and olfactory identification, respectively.
Olfactory identification relies on the brain to help work out what the smell is and suggests that neurological function may help to explain the relationship between smell and frailty.
Dr Rowan said: "We use our sense of smell to identify the threat of a fire or to enjoy the fragrance of flowers on a spring day. But just like vision and hearing, this sense weakens as we age.
"We found that both impaired olfactory identification and sensitivity functions are associated with frailty, which is interesting because it shows that it's not just your ageing brain at work here, but it may also be something peripheral, like something at the level of your nose that is able to predict our impending frailty and death."
However, exactly how worsening smell is linked to declining health remains to be seen
Common consequences of smell loss include a loss of appetite, difficulty monitoring personal hygiene, depression and an inability to detect toxic fumes.
For older adults, it can also lead to weight loss, malnutrition, weakness, inadequate personal care and even potential injuries caused by gas leaks or fires.
Frailty is a key marker of old age and declining health and can be delayed with exercise, good habits and a healthy diet.
Loss of senses is a common indicator of poor health, with hearing loss, for example, linked to Alzheimer’s.
Dr Sarah Bauermeister, senior scientist at Dementia Platforms UK and an academic at the University of Oxford, is calling for people to get regular hearing checks throughout their life to spot any auditory decline which may be a harbinger of future Alzheimer’s.
Hearing loss, she says, is the single biggest factor which can increase a person’s risk of the degenerative condition.
“Regular hearing checks are very important, and this is across the lifespan, so that it’s normalised to have a hearing check, whether you are 30 or 40 years old,” she said.
“If we normalise hearing checks, it will normalise the wearing of a hearing aid and the stigma will then be reduced.”