A COMMON symptom that plagues those with Covid could in fact be an early sign of a killer condition.
Loss of smell occurs in around one fifth of people who get the virus, and plagues millions more after recovery.
Losing your sense of smell? Research suggests it may be more serious than long Covid
Studies show that one in 20 people who catch Covid may permanently lose their sense of smell or taste (anosmia).
But new research warns that losing sense of smell may be a signal for dementia, of which the most common form is Alzheimer’s.
The disease, which causes the memory to slowly vanish, is the leading cause of death in the UK.
It’s diagnosed in one in six people over the age of 80, but can start developing years before.
And researchers have now said a rapid loss of smell is a “really good indicator” of what’s going on in the brain, including dementia risk.
Memory plays a critical role in our ability to recognise smells – you can remember a person or time in your life by a whiff passing you by.
Scientists say that the build-up of proteins that kill brain cells in the development of Alzheimer’s disease often appear in parts of the brain related to smell first.
It’s still unknown if this damage actually causes the decline in a person’s sense of smell.
Rachel Pacyna, lead author of the study, said: “Our idea was that people with a rapidly declining sense of smell over time would be in worse shape –and more likely to have brain problems and even Alzheimer’s itself –than people who were slowly declining or maintaining a normal sense of smell.”
The medical student and a team at the University of Chicago Pritzker School of Medicine studied more than 500 adults who had signed up to a study in 1997.
They found a drop in smelling abilities during a period of normal cognition predicted multiple features of Alzheimer’s disease.
People with deteriorating sense of smell had smaller grey matter volume in the areas of the brain related to smell and memory, brain scans showed.
They also had worse cognition and higher risk of dementia, according to the findings published in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association.
The researchers claimed the risk of sense of smell loss was similar to carrying the APOE-e4 gene, a known genetic risk factor for developing Alzheimer’s.
But there are dozens of risk factors for dementia, including genetics, poor lifestyle choices and education level.
Senior author Dr Jayant Pinto, an ear nose and throat (ENT) specialist, previously found that older adults with no sense of smell were three times more likely to die within five years.
Dr Pinto said: “Sense of smell and change in the sense of smell should be one important component in the context of an array of factors that we believe affect the brain in health and ageing.”
The professor of surgery at the University of Chicago said he hoped that in the future, testing someone’s sense of smell could be used to detect those at risk of dementia as early as possible.
This would involve something like reporting the smell of a scented stick.
Ms Pacyna said: “If we could identify people in their 40s, 50s and 60s who are at higher risk early on.”
Previous research has shown that those who have difficulty identifying four out of five smells (peppermint, fish, orange, rose and leather) were twice as likely to develop the dementia within five years.
But a contradictory 2001 study found that people with Dementia or Alzheimer’s were no less likely than others to develop anosmia.
Alzhiemer’s is incurable – once you have it, there is no way of getting rid of it and the progression is slow over many years.
Generally, you can slash dementia odds by eating a healthy diet, exercising, not smoking and limiting alcohol.
There are currently around 900,000 people with dementia in the UK, most of which will have Alzheimer’s.
And worldwide, there are 57.4 million – a figure expected to more than double to 152.8 million by 2050.