ALZHEIMER'S is a devastating condition for those who have it and their families.
But experts have warned that there is one warning sign that could double your risk of the condition.
Alzheimer's is a brain disease that causes a slow decline in memory, thinking and reasoning skills.
The disease progresses in several stages: preclinical, mild (sometimes called early-stage), moderate, and severe (sometimes called late-stage).
A long-term study of almost 3,000 adults aged between 57 and 85 found that those who could not identify at least four out of five common smells were more than twice as likely to develop the disease within five years.
The five odours, in order of increasing difficulty, were peppermint, fish, orange, rose and leather.
Most people, about 78 per cent, were able to correctly identify at least four out of the five scents but 14 per cent could only name three, five per cent could name two, two per cent could name one and one per cent were unable to name any.
Five years later almost all of the people who couldn't identify any of the smells had been diagnosed with dementia.
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And nearly 80 per cent of those who could only name one or two scents had also developed the disease.
Lead author on the 2017 study, Jayant Pinto, a professor of surgery at the University of Chicago, said: "These results show that the sense of smell is closely connected with brain function and health.
"We think smell ability specifically, but also sensory function more broadly, may be an important early sign, marking people at greater risk for dementia."
Dementia begins when the brain is damaged by diseases, such as Alzheimer's or a series of strokes.
Alzheimer's disease is the most common cause of dementia – but not all dementia is down to Alzheimer's.
Another study published in 2015 also looked into the connection between odour and Alzheimer disease biomarkers in the clinically normal elderly.
It found that in 'clinically normal' individuals, worse odour identification was linked with markers of neurodegeneration.
This is the progressive loss of function of neurons, which is present in diseases such as Alzheimer's disease and Parkinson's disease.
What are the signs and symptoms of Alzheimers?
In the early stages of disease, the signs may be subtle at first.
However, over time they become more pronounced and begin to interfere with a person’s daily life.
While there are common symptoms, every person diagnosed with Alzheimer’s is unique and will likely experience the disease differently.
But, for most, the earliest sign are problems with memory. Here are the five you should look out for.
As the disease progresses a person might:
- lose common items including keys and glasses around the house
- struggle to find the word they are looking for in conversation
- forget recent conversations or events
- get lost in a familiar place, or while on a familiar journey
- forget important anniversaries, birthdays or appointments
Though memory problems are the most common, there are other signs a person may be struggling with dementia.
They include:
- speech problems – a person may struggle to follow a conversation or find they are often repeating themselves
- problems judging distance, navigating stairs or parking the car
- difficulties making decisions and solving problems
- losing track of the day or date
The study was published in the American Academy or Neurologyand found that odour detection is linked to being able to detect preclinical Alzheimer's in those who have no other underlying medical conditions.
Over the last 18 months, a loss of taste and smell have largely been associated with the coronavirus.
In May 2020 if was officially listed as one of the key symptoms of the virus.
A 2001 study actually found that people with Dementia or Alzheimer's were no less likely than others to develop anosmia (loss of taste or smell).
The researchers did state that patients with Lewy bodies were more likely to be anosmic than those with Alzheimer's disease or controls.
The NHS states that Dementia with Lewy bodies (DLB), also known as Lewy body dementia, is one of the most common types of dementia.
The guidance states: "People with dementia with Lewy bodies may have hallucinations – seeing, hearing or smelling things that are not there."
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While many studies have looked at the link between smell and Dementia, the Alzheimer's society states that no singular tests can diagnose the condition.
They state: "Doctors use a range of different examinations; the strengths and weaknesses of new tests need to be compared to existing methods to understand where improvements can be made."
Olfactory deficits are often an early sign of Alzheimer's disease or Parkinson's disease and they get worse with disease progression.
Pinto added that losing the ability to smell can have a detrimental impact on a persons health and wellbeing.
"Smells influence nutrition and mental health," he added.
"People who can't smell face everyday problems such as knowing whether food is spoiled, detecting smoke during a fire, or assessing the need a shower after a workout.
"Being unable to smell is closely associated with depression as people don't get as much pleasure in life."
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