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Loss of Smell in Parkinson’s Research


Smell Loss in Parkinson’s disease Research Project

Peter A. LeWitt, M.D.
Professor of Neurology, Wayne State University School of Medicine
Director, Parkinson's Disease and Movement Disorders Program
Henry Ford Hospital - West Bloomfield


We wish to study the early signs of Parkinson’s disease (PD) because detecting the onset of Parkinson’s at its earliest stages may help physicians develop more effective treatments. We are targeting the sense of smell and smell memories because changes in these measures have been implicated as early signs of Parkinson’s disease.

Impaired sense of smell is very common among PD patients. In fact, decreased acuity in recognizing odors (known as hyposmia) is so common that as many as 90% of PD patients experience it. It can be a subtle development for some patients that this sense has diminished, or that certain foods no longer have the same smell as before. Research indicates that smell loss can be an early sign of PD, one that may manifest several years before the onset of motor symptoms, such as tremor and slowed movement. The presence of smell loss does not always mean a person will go on to develop PD; however one investigation found that participants with the most profound smell loss were five times more likely to develop PD than those without this problem.

The reasons for this association are unclear. One theory by researcher Heiko Braak may offer insight. According to this theory, the pathological changes associated with PD first appear in areas such as the gastrointestinal tract and the olfactory bulb (the region of the brain that controls our sense of smell). The theory is that an abnormal protein (alpha-synuclein aggregates which are lethal to nerve cells in the PD brain) initially develop in these regions, causing local damage before spreading to other regions of the brain controlling movement. This may explain why smell loss and other non-motor symptoms of PD (such as chronic constipation) often precede motor symptoms.

Smell loss can significantly impact quality of life for PD patients. Enjoyment from smelling and tasting food can be diminished (and this may lead to weight loss or nutritional deficiencies). Safety can also be of concern with smell loss, as there may be difficulty smelling spoiled food or noxious substances. Unfortunately, treatments for smell loss are limited. In particular, treatment for PD doesn’t benefit smell loss. Rarely, deep brain stimulation (DBS) has improved smell loss in some patients. In addition, smell training (smelling certain odors twice a day for several weeks) has shown promise in improving sense of smell in PD patients. More research is needed, however, to evaluate effective treatments for smell loss.

Investigating the connection between smell loss and PD may help researchers learn more about the cause and treatment of this disorder. Studying the early signs of PD, such as smell loss, is particularly important because it may lead to improved efforts for early detection. As new treatments for halting PD become available in the future, early diagnosis may be a critical need.

In this study, we are testing those who have been recently diagnosed with Parkinson’s disease and those who have not. If you fit that criteria, we would like to invite you as well as your spouse, friends, or family members to participate in this study at not cost. Participation would involve one visit to the clinic and would require no more than 2 hours and 30 minutes. The study is being conducted at Parkinson’s Disease and Movement Disorders Center at Henry Ford Hospital in West Bloomfield.

In this study, you will be asked to complete smell tests in which you will be asked to identify odors, such as the smell of coffee. In addition, you will be asked to complete tests on thinking capacity.

If you would like to learn more about participating in this research study, please contact Peter LeWitt MD at 248-661-6540 for more information.

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