Mild cognitive impairment (MCI) is often the first stage of Alzheimer’s development and a primary symptom is the inability to differentiate between scents.
Memory is a basic function of your brain. If your cells are healthy, they communicate back and forth to your hippocampus – your brain’s filing room – dropping memories in and taking them back out as needed. As we age that process takes longer because we don’t have as many brain cells working together.
Neuro-degenerative diseases such as Alzheimer’s further disrupt this communication as plaque – small clusters of protein – builds up to toxic levels.
Eventually, patients are unable to access that filing room at all. The area of the brain responsible for processing smell is one of the first affected in Alzheimer’s patients.
Plaque Removal Restores Sense of Smell
Case Western Reserve University School of Medicine recently found that removing plaque in the brain restored rats’ sense of smell. Their study was published in The Journal of Neuroscience.
Daniel Wesson, assistant professor of neuroscience, explains, “’The evidence indicates we can use the sense of smell to determine if someone may get Alzheimer’s disease, and use changes in sense of smell to begin treatments, instead of waiting until someone has issues learning and remembering. Understanding smell loss, we think, will hold some clues about how to slow down this disease.”
The plaque accumulates in parts of the brain responsible for smell long before it shows up in the areas responsible for loss of cognition, coordination and memory.
Even amounts of this plaque too small to be detected by a brain scan affected the rats’ ability to smell but was still caught early enough that the rest of their brain function was not yet impaired.
The mice were given a drug that flushes these plaque deposits from the brain. Their sense of smell returned within weeks only to deteriorate rapidly when the drug therapy was stopped. Wesson explained, “This shows the unique vulnerability of the olfactory system to the pathogenesis of Alzheimer’s disease.”
Earlier detection of this toxic plaque in human brains could mean Alzheimers prevention.
The Importance of Smell
In a recent cooperative study between Rush University and the University of Pennsylvania published in Archives of General Psychiatry, researchers discuss the link between loss of smell and cognitive decline in older people.
Chosen participants showed no sign of cognitive decline. Their sense of smell was monitored at the start of the study, then each year thereafter for five years.
Brain function tests, as well as neurological and physical exams, were also given to the 589 subjects each year. 12 familiar odors were used to measure their sense of smell followed by a choice of four possible answers.
By the end of the study, 30% [177 participants] showed a decline in their sense of smell and also developed MCI – specifically showing difficulty perception and remembering experiences, ideas, words or symbols. In fact, as their ability to smell declined, so did their cognitive function.
Researchers concluded that subjects with a poor sense of smell were 50% more likely to develop MCI – making their risk of developing Alzheimer’s disease much higher than those who scored average or well on their smell tests.
They are hopeful that smell tests will become a useful tool in early diagnosis of neurodegenerative illnesses such as MCI, Alzheimer’s and Parkinson’s.
Neurodegenerative diseases affect more than 40 million people worldwide and there are currently no cures.
Alzheimer’s patients experience a gradual decline in their senses, memory loss, overall coordination problems and personality changes.
As more about the biology of the brain is learned, Alzheimers prevention and other brain function illnesses becomes possible. The quality and effectiveness of current treatment is already improving.
Fighting these diseases effectively is promising; figuring out how to prevent them entirely will be even better.
Scents You Can Use at Home to Test Your Sense of Smell
If you have difficulty identifying the scents listed above, you should speak to your doctor.
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