As part of my PhD research project on non-motor symptoms in Parkinson’s disease, I often speak to patients and their families or caregivers, who always seem eager to learn more about this aspect of the disease.
Recently, a patient’s wife asked about a number of non-motor symptoms her husband experienced for several years before his diagnosis. She wondered whether these problems were early clues to his underlying Parkinson’s disease.
The truth is that neurologists don’t know for sure if these problems increase the risk for Parkinson’s disease or are pre-clinical signs or symptoms of the disease itself. But, I can share what we now know about these non-motor symptoms.
1. Rapid eye movement (REM) sleep behavioral disorder (RBD): This is a sleep disorder in which people act out their dreams due to a lack of normal paralysis during the dreaming, or so-called REM, stage of sleep. RBD can be identified through a formal study called polysomnography, in which experts monitor important physiological signs such as oxygen levels during sleep. In a recent study in Neurology, about 70 percent of patients with RBD showed signs of a neurodegenerative disease 10 years later.
2. Loss of smell: Our sense of smell diminishes with age, but it can also diminish because of Parkinson’s disease. In fact, about 75 to 90 percent of people with Parkinson’s disease may lose their sense of smell, according to a recent study in Parkinsonism and Movement Disorders. Neurologists can assess sense of smell with tools such as the University of Pennsylvania Smell Identification Test.
3. Postural hypotension: About 25 percent of people with Parkinson’s disease experience postural hypotension, according to a 2016 study in Movement Disorders Clinical Practice. Hypotension happens when the blood pressure drops rapidly and significantly upon standing from a sitting or lying position. This can be especially dangerous if the patient also falls or passes out.
4. Depression and anxiety: These symptoms often occur in tandem and are associated with many different neurologic conditions, including Parkinson’s disease. Excessive daytime fatigue, which can occur on its own or alongside depression, may also be a possible precursor.
5. Constipation: Having fewer bowel movements can occur as part of preclinical autonomic dysfunction—or difficulty regulating the part of the nervous system that helps control many bodily functions such as heart rate and urination.
Some experts believe the order and sequence of these symptoms could reflect the natural progression of Parkinson’s disease-related degeneration in the brain. However, it is usually impossible to ascertain the precise order in which these signs and symptoms occur, and not all patients can recall having these problems. Larger studies that begin tracking individuals before diagnosis will be necessary to answer the many remaining questions.
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