Medical Myths: All about Parkinson’s disease
Written by Tim Newman on April 5, 2021 — Fact checked by Anna Guildford, Ph.D.
April is Parkinson’s Awareness Month. With this in mind, this week’s edition of Medical Myths tackles the many misunderstandings that surround Parkinson’s disease. We discuss the symptoms and treatment, the outlook for people with the condition, and more.
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Parkinson’s disease is a neurodegenerative movement disorder. Over time, dopamine-producing cells in a part of the brain called the substantia nigra deteriorate.
This deterioration, which leads to a reduction in dopamine, produces symptoms. The symptoms tend to develop slowly over time, often starting with a slight tremor in one hand or stiffness in movement.
Aside from tremor and stiffness, other symptoms include difficulties coordinating movements, changes in posture, a fixed facial expression, a reduced sense of smell, mood changes, and sleep problems.
As the disease progresses, some people with Parkinson’s develop dementia.
In 2016, an estimated 6.1 million people worldwide had Parkinson’s disease. The number of cases has more than doubled in the last 25 years.
In this article, we dispel some of the most common myths associated with Parkinson’s disease.
1. Parkinson’s only affects movement
It is true that the medical community considers Parkinson’s disease a motor disorder. However, people with the condition often also experience nonmotor symptoms, which can begin before the motor symptoms.
Nonmotor symptoms can include cognitive impairment or dementia, depression and anxiety, sleep dysfunction, pain, apathy, sexual dysfunction, and bowel incontinence.
People often overlook these symptoms, but they are important. As the authors of one paper on the topic explain:
“[N]onmotor symptoms dominate the clinical picture of advanced Parkinson’s disease and contribute to severe disability, impaired quality of life, and shortened life expectancy.”
2. Treatment only works for a few years
Although there is no cure for Parkinson’s disease, drugs can help people manage the condition. One of the most effective drugs is levodopa, which the body converts into dopamine once it enters the brain.
There is a long standing myth that levodopa can only relieve symptoms for about 5 years before it stops working. This is a myth. Levodopa can be effective for decades. However, over time, its effectiveness might reduce.
Medical News Today spoke with James Beck, Senior Vice President and Chief Scientific Officer of the Parkinson’s Foundation. He explained why levodopa becomes less potent:
“One of the cruel ironies about Parkinson’s disease is that the key enzyme that converts levodopa to dopamine (aromatic acid decarboxylase or AADC) is predominantly found in the dopamine neurons of the substantia nigra, which are lost during progression of the disease. So, the main way to make dopamine available to the Parkinson’s brain declines as the disease advances.”
In other words, it is not that levodopa stops being effective. Instead, the supply of the enzyme that it needs to be effective becomes more limited.
In the past, doctors and people with Parkinson’s have held off starting treatment because of fears that levodopa would slowly stop working. We now know, though, that this reduction in potency is due not to the length of time that a person takes levodopa but to the progression of the disease.
However, it is true that over time, each dose of levodopa might improve symptoms for a shorter period. This so-called wearing-off means that symptoms start to return before the next dose is due.
3. Levodopa makes symptoms worse
Another misconception about levodopa is that it can make Parkinson’s disease symptoms worse. This is not true.
It is important to note that levodopa can cause other motor symptoms, such as dyskinesia, which refers to involuntary jerky movements. However, the onset of dyskinesia is related to the progress of the underlying disease rather than how long an individual has been taking levodopa.
Therefore, doctors no longer recommend holding off on taking levodopa until later in the disease.
According to the American Parkinson’s Disease Association (APDA), dyskinesia does not generally appear until the individual has been taking levodopa for 4–10 years. The APDA also writes:
“Dyskinesia in its milder form may not be bothersome, and the mobility afforded by taking levodopa may be preferable to the immobility associated with not taking levodopa. People with Parkinson’s must weigh the benefits from using levodopa versus the impact of dyskinesia on their quality of life.”
4. Tremor always signifies Parkinson’s
Tremor is the most well-known symptom of Parkinson’s disease. However, it can also occur as part of other conditions, including drug-induced parkinsonism, vascular parkinsonism, dystonic or essential tremor, psychogenic disease, and dopa-responsive dystonia.
5. Doctors can always provide an accurate outlook
Although doctors understand the range of symptoms that are associated with Parkinson’s, it is very difficult to predict how an individual’s disease will progress. Parkinson’s varies substantially among individuals.
As the authors of one study explain, there are “radical differences in clinical manifestations and progression between patients.”
“The [reason for the] differences observed in how individuals experience Parkinson’s disease and its progression remains unknown.” Dr. Beck explained to MNT. “It could be based on how Parkinson’s began with each individual.”
Scientists are currently investigating ways of making better predictions. Hopefully, in the future, doctors will be able to provide a clearer idea of how an individual’s condition will progress.