According to recent research, a simple smell test can accurately predict dementia symptoms five years before they appear. A study of nearly 3,000 older people found that those who could not identify at least four of five common odors were more than twice as likely to have the disease.
The worse their sense of smell, the greater the risk, the scientists said. Aromas are mint, fish, orange, rose and leather depending on the difficulty level and can be used as an early warning system.
This will allow medications and lifestyle changes, such as a healthy diet and more exercise, to be more effective before the devastating condition occurs. The findings add to growing evidence that the initial damage in the brain occurs in olfactory neurons that distinguish different aromas.
Five years after the first test, nearly all the participants, who ranged in age from 57 to 85 and could not name a single smell, were diagnosed with dementia. And almost 80 percent of those who gave only one or two correct answers did so.
Overall, the degree of smell loss was significantly related to the incidence of the disease. Lead author Professor Jayant Pinto, from the University of Chicago, said: “Our testing just signals that someone should pay closer attention.
“A lot more work needs to be done to make this a clinical test. But it could help find people who are at risk. We could then enroll them in early-stage prevention studies.”
“Of all the human senses, smell is the most undervalued and underappreciated—until it’s gone. These results show that the sense of smell is closely linked to brain function and health.”
“We think that the ability to smell specifically, but also sensory function more broadly, may be an important early marker that puts people at greater risk for dementia.”
Almost eight in ten (78%) of those tested were normal, correctly identifying at least four out of five odors. However, 14 percent could not smell only three, five percent could not smell two, two percent could not smell one, and one percent could not smell even one.
The ear, nose and throat surgeon, who studies the genetics and treatment of olfactory and sinus diseases, added: “We need to understand the underlying mechanisms so that we can understand neurodegenerative disease and develop new treatments and preventive interventions.
“Loss of the sense of smell is a strong sign that something is wrong and serious damage has occurred. This simple smell test can provide a quick and inexpensive way to identify people who are already at high risk.”
The study, published in the Journal of the American Geriatrics Society, follows a related paper from 2014 in which olfactory impairment was associated with an increased risk of death within five years. In this study, loss of the sense of smell was a better predictor of death than a diagnosis of heart failure, cancer, or lung disease.
In both studies, researchers used a validated tool known as the “Sniffin’Stick,” a marker-like tool infused with different scents.
Participants smell each item and then identify that scent one by one from four options. Those who achieved two or three correct answers were considered “hyposmic,” defined as a diminished sense of smell, while those who achieved one or none were labeled “anosmic,” who had completely lost the sense of smell.
The olfactory nerve is the only cranial nerve directly exposed to the environment. The cells that detect odors connect directly to the olfactory bulb at the base of the brain.
This potentially exposes the central nervous system to environmental hazards such as pollution or pathogens. Smell problems are often an early symptom of Parkinson’s or Alzheimer’s disease and get worse as the disease progresses.
Prof Pinto said losing the ability to smell could have a significant impact on lifestyle and wellbeing. He explained: “Smells affect nutrition and mental health.
“People who can’t smell face daily challenges such as detecting whether food has spoiled, detecting smoke during a fire, or assessing the need to shower after a workout.
“Not being able to smell is closely associated with depression because people cannot enjoy life as much.”
Loss of the sense of smell is one of the early signs of dementia, which can only be diagnosed after death. “This evolutionarily ancient specialized sense may signal an important mechanism that also underlies human cognition,” said Martha McClintock, professor of psychology at the University of Chicago.
He stated that the olfactory system also has self-renewing stem cells. Prof McClintock added: “A decline in the ability to smell may indicate a reduction in the brain’s ability to regenerate essential components that decline with age, which can lead to pathological changes in many different types of dementia.”
A Canadian study last month of 300 people at high risk of developing Alzheimer’s found that those who had trouble distinguishing the smells of gum, petroleum and lemon were more likely to have dementia-related proteins in their cerebrospinal fluid.
Around 850,000 people in the UK have dementia; Due to the aging population, this figure is expected to increase to one million in 2025 and two million in 2050.