What Is Parkinson’s Disease? Symptoms, Causes, Diagnosis, Treatment, and Prevention
Parkinson’s disease is a movement disorder that happens when nerve cells (neurons) in a certain part of the brain are no longer making the chemical dopamine.
The condition is also sometimes known as paralysis agitans or shaking palsy.
The Parkinson’s Foundation estimates that nearly 90,000 Americans are diagnosed with Parkinson’s every year. But the true number of people who develop the disease may be much higher. (1)
Symptoms and possible treatments for Parkinson’s were discussed in texts related to Ayurveda, an ancient Indian medical practice that’s been around since as early as 5,000 BCE. (2) A Parkinson’s-like condition was also mentioned in the first Chinese medical text, the Huangdi Neijing, more than 2,500 years ago.
Parkinson’s disease was formally recognized in an 1817 paper, “An Essay on the Shaking Palsy,” by James Parkinson, a London apothecary-surgeon and member of the Royal College of Surgeons. (3)
Parkinson (1755–1824) observed what are now known as the classic symptoms of Parkinson’s disease, including tremors, rigidity, and postural instability. He theorized that the disease developed because of a problem in the brain’s medulla region.
Parkinson’s essay received little attention until 1861, when French neurologist Jean-Martin Charcot and his colleagues distinguished the disease from other neurological conditions and termed it “Parkinson’s disease.” (3)
Parkinson’s disease is the most common cause of parkinsonism, a category of neurological diseases that cause slowed movement. (4) Parkinsonism may appear very similar, but it is not caused by Parkinson’s disease. It develops as a result of other neurological diseases or injury, such as stroke or traumatic brain injury.
No quick or easy diagnostic tests exist for Parkinson’s disease, so a patient may receive an initial diagnosis of parkinsonism without a more specific condition being confirmed.
Classic Parkinson’s disease — referred to as idiopathic because it has no known cause — is the most common and most treatable parkinsonism.
About 15 percent of people with parkinsonism have atypical variants, which are also known as Parkinson’s-plus syndromes. (5)
Among the most common nonmotor symptoms are:
The primary symptoms of Parkinson’s disease — tremors, muscle stiffness, slow movement, and impaired balance — can vary from person to person depending on what subtype of Parkinson’s they have, but they generally get worse over time. The three Parkinson’s subtypes are: (20)
Parkinson’s symptoms often begin on one side of the body and gradually affect both sides of the body, but they tend to be worse on the side they affected first.
Learn More About Signs and Symptoms of Parkinson’s Disease
Neurologists usually describe the progression of Parkinson’s symptoms in stages, using the system known as the Hoehn and Yahr scale. (6) These stages are:
Most cases of Parkinson’s disease are idiopathic, meaning the cause is unclear.
It’s widely believed that a person with Parkinson’s may be genetically vulnerable to the disease and that one or more unknown factors in the environment eventually triggers it.
Most of the symptoms of Parkinson’s disease come from the loss of neurons in an area of the brain called the substantia nigra. (7)
Normally, the neurons in this part of the brain make the chemical messenger (neurotransmitter) dopamine, which allows communication with another area of the brain, the corpus striatum.
This communication helps produce smooth, purposeful movement. When the neurons in the substantia nigra die, the resulting loss of communication leads to the motor (movement-related) symptoms of Parkinson’s. (8)
Although the cause of this cell death is unknown, many researchers believe that the cells are killed by clumped proteins called Lewy bodies. (8)
The affected neurons of people with Parkinson’s disease have been found to contain clumped proteins called Lewy bodies. (9) Researchers aren’t yet sure why Lewy bodies form or what role they play in the disease, but Lewy bodies are believed to be toxic. (9)
Lewy bodies are clumps of a protein called alpha-synuclein. Neurons can’t break down these protein clumps, which may lead to the death of these cells. (9)
Some other theoretical causes of brain cell death in people with Parkinson’s disease include free-radical damage, inflammation, or toxins.
Learn More About Lewy Body Dementia
Risk factors for Parkinson’s disease include:
Genetics
People with a first-degree relative (parent or sibling) with Parkinson’s are at an increased risk for the disease — possibly as much as 9 percent greater. Genetic risk factors (the presence of certain genes associated with Parkinson’s disease) are more commonly seen in early-onset Parkinson’s.
Fifteen percent of people with Parkinson’s have a known relative with the disease, but a condition called familial Parkinson’s, which has a known genetic link, is relatively rare. (10)
Age
The average age of onset is 60, and the incidence rises with advancing age. About 4 percent of people have “early-onset” or “young-onset” disease, which begins before age 50. (11)
Gender
Parkinson’s affects about 50 percent more men than women, for unknown reasons. (12)
Pesticide Exposure
Exposure to some pesticides has been shown to raise the risk of developing Parkinson’s.
Problematic chemicals include organochlorine pesticides like DDT, dieldrin, and chlordane. Rotenone and permethrin have also been implicated. (13)
Fungicide and Herbicide Exposure
Exposure to the fungicide maneb or the herbicides 2,4-dichlorophenoxyacetic acid (2,4-D), paraquat, or Agent Orange may raise the risk of Parkinson’s.
The U.S. Department of Veterans Affairs considers Parkinson’s to be a possible service-related illness if the person was exposed to significant amounts of Agent Orange. (14)
Head Injuries
Recurrent head injuries, particularly repetitive head injuries, may contribute to the development of Parkinson’s in some people. (15)
Coffee and Smoking
People who drink coffee or smoke tobacco in moderation have been found to have a lower risk of Parkinson’s disease, for reasons that remain unclear. (16) But while smoking could potentially lower the risk for Parkinson’s disease, it clearly increases the risk for lung cancer and cardiovascular disease, including heart attacks and stroke.
There aren’t any specific tests to diagnose someone with Parkinson’s disease.
Doctors typically make a diagnosis based on the following:
Sometimes, people who have a known inherited form of Parkinson’s disease can take a gene test to determine their risk for developing the disease. (17,18)
As Parkinson’s progresses, symptoms often worsen. Some people who respond well to therapy have minimal disability issues. Others, however, become severely incapacitated.
Although Parkinson’s isn’t considered a fatal disease itself, it can cause life-threatening complications that may shorten your lifespan.
Today, most people living with Parkinson’s disease have close to a normal life expectancy. (19)
Once you have Parkinson’s, you can’t get rid of it. But there are many effective therapies to help control your symptoms and limit disability. Research shows you can live many years with Parkinson’s disease. (19)
For decades, doctors couldn’t treat Parkinson’s disease effectively and thought it was a terminal illness. In the late 19th century, arsenic, morphine, hemlock, and cannabis were used to treat tremors. (3)
By the 1940s and 1950s, neurosurgeons had begun to perform surgery on the basal ganglia of the brain, which resulted in improvements in Parkinson’s disease symptoms. While this surgery was sometimes effective, it was also risky — about 10 percent of patients died as a result of the operation. (3)
The biggest advance in Parkinson’s treatment came in the 1960s. Researchers identified differences in the brains of people with Parkinson’s associated with low levels of the chemical dopamine, which plays a role in coordinated movement. (3)
There’s no cure for Parkinson’s, but a number of treatments can help manage the disease’s symptoms. (17)
Medications for Parkinson’s disease fall into three general categories:
Treating Parkinson’s disease with medication can be a balancing act between managing the disease and managing drug side effects.
Learn More About Medications for Parkinson’s Disease
Deep brain stimulation surgery is an option for people with Parkinson’s disease who no longer respond to medications. This is most effective at treating severe tremors that impact a person’s ability to function.
With this method, doctors implant electrodes in specific areas of the brain. The electrodes connect to a generator that’s implanted in the patient’s chest. The generator sends electrical pulses to the brain, which help reduce symptoms. (17,18)
Some people with Parkinson’s disease use complementary therapies to manage their symptoms.
These approaches may include:
Learn More About What to Eat if You Have Parkinson’s Disease
Researchers don’t know of any proven ways to prevent Parkinson’s disease, but avoiding certain risk factors and adopting a healthy lifestyle may reduce your risk.
Some studies have shown a diet high in antioxidants along with regular exercise may play a role in preventing Parkinson’s. Other findings have suggested that compounds like caffeine (No Doz), niacin (Nicotinic Acid), and nicotine (Thrive) may have a protective effect against Parkinson’s disease. (21)
Researchers have studied various formulations of nicotine — including intranasal, transdermal, and chewing gum — to see whether they could help with Parkinson’s symptoms, but so far none has been found effective at slowing the progression of Parkinson’s.
Parkinson’s disease can increase your risk of developing complications such as falls, choking, and pneumonia.
Nearly 1 million people in the United States are living with the disease. More than 10 million people worldwide have Parkinson’s. (1)
About 4 percent of people with Parkinson’s are diagnosed before age 50. (1)
Men are 1.5 times more likely to develop the disease than women. (1)
Some research suggests that Parkinson’s disease is more likely to affect white and Hispanic people than African Americans. (22) But other studies have indicated that the prevalence of Parkinson’s among African Americans is similar to that of white people. (23,24,25)
African Americans remain underrepresented in Parkinson’s-related research studies, which may contribute to the discrepancies in these estimates.
African American patients may also be less likely to receive proper care for the disease, research shows.
A study published in 2021 showed that Black people with Parkinson’s were, on average, four years older at the time they received their diagnosis than white people with this condition. (23)
The study also revealed racial disparities when it comes to diagnosis, treatment, survival, and medication use that negatively impact Black people compared with white people who have Parkinson’s.
For example, Black people were more likely to receive care for Parkinson’s through the emergency department than white people and were less likely to be taking medications for parkinsonism and mood disorders than white people. (23)
These disparities likely result from factors such as health insurance status and access to medical care, among others. (24,25)
Many conditions can cause symptoms that are similar to those of Parkinson’s disease, including the following:
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