Parkinson’s disease, a neurodegenerative disorder affecting millions worldwide, is often recognized by its more obvious motor symptoms – tremors, stiffness, and slower movements.
However, many people don’t realize that a significant number of Parkinson’s patients – between 75% to 90% – also report a loss of smell, often even before the motor symptoms appear.
This loss of smell, technically known as anosmia, is a non-motor symptom of Parkinson’s that has, until recently, been less studied.
Now, researchers at Yale School of Medicine have shone a light on this issue, making fascinating discoveries about how Parkinson’s impacts our sense of smell.
The Hunt for Biological Clues
To understand why anosmia happens in Parkinson’s patients, scientists from the Greer Lab and Chandra Lab at Yale School of Medicine turned to a special kind of mouse.
These mice are genetically modified to mimic the symptoms of Parkinson’s, thanks to a mutation known as alpha-synuclein A30P.
The researchers performed a “buried food test” to assess the olfactory ability – the ability to smell – of these mice.
They found that the mice with later-stage symptoms of Parkinson’s disease had trouble finding the food, suggesting a diminished sense of smell.
What’s Happening in the Brain?
When they examined the brains of these mice, the researchers found significant damage to certain nerve cells, or neurons, involved in the sense of smell.
These damaged neurons were in a part of the brain called the olfactory bulb, which processes information about odors.
Furthermore, they noticed that these mice had reduced neurogenesis in the olfactory bulb. Neurogenesis is the process by which new neurons are created.
Interestingly, it is known that even in normal aging brains, new neurons continue to form in the olfactory bulb throughout a person’s life.
Why is This Important?
According to Dr. Charles Greer, one of the study’s authors, Parkinson’s patients had been reporting diminished sense of smell for years.
However, the focus of research has often been on the more debilitating motor symptoms. But with these new findings, scientists are starting to understand more about the non-motor symptoms, including anosmia.
Co-author Dr. Sreeganga Chandra shares this excitement, emphasizing the importance of understanding the basis of anosmia in Parkinson’s patients.
Indeed, the implications of these findings could be huge. As Dr. Greer suggests, “These findings could help in developing a very early diagnostic tool for the disease.”
This is because some Parkinson’s patients report a loss of smell up to ten years before their diagnosis.
Understanding the mechanisms behind this symptom could potentially lead to earlier detection and intervention for those living with this life-changing disease.
If you care about Parkinson’s disease, please read studies about Vitamin E that may help prevent Parkinson’s disease, and Vitamin D could benefit people with Parkinson’s disease.
For more information about brain health, please see recent studies about new way to treat Parkinson’s disease, and results showing COVID-19 may be linked to Parkinson’s disease.
The study was published in The Journal of Neuroscience.
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