Parkinson’s Disease: News on Causes, Prevention, and Treatment

Prianka Waghray, Brandel France de Bravo, MPH, National Center for Health Research

Prianka Waghray, Brandel France de Bravo, MPH, Avery Nork, Sophia Phillips, MS, Ashley Hystad, National Center for Health Research

Nearly 90,000 people in the U.S. are diagnosed with Parkinson’s Disease each year. This is a 50% increase from the 60,000 diagnosed in the U.S. in previous years.1 By 2030, approximately 1.2 million people in the U.S. will be living with the disease. People with traumatic brain injuries (TBI) and people exposed to pesticides are more likely to develop Parkinsons.2,3 And, a study published in 2023 reports the people exposed to a common chemical, trichloroethylene (TCE), are also more likely to develop Parkinson’s.

What is Parkinson’s Disease?

Parkinson’s disease is one of the most common nervous system disorders and affects 1-2% of the population over 65 years of age. Parkinson’s is a chronic neurological disorder, which means that it affects a patient’s nervous system and gets worse over time.4

A person with Parkinson’s may have difficulty walking, chewing, speaking, and moving their arms and legs. There are four (4) common symptoms associated with Parkinson’s:

  • Tremors and trembling hands, legs, jaw and arms
  • Stiffness of the arms, legs and body
  • Inability to move fast
  • Lack of balance and coordination

Other symptoms include cognitive impairment and emotional changes, including depression.

There is no one cause of Parkinson’s disease, and environmental exposures may contribute to developing the disease.

Trichloroethylene (TCE)

A 2023 article examining numerous case studies and animal research studies found that a chemical known as TCE used in paint removers, gun cleaners, aerosol cleaning products, and dry cleaning is associated with as much as a 500% increased risk for Parkinson’s disease. The article’s lead researcher, Dr. Ray Dorsey, from the University of Rochester, called Parkinson’s disease “the world’s fastest-growing brain disease” and that it “may be largely preventable.”5

Unfortunately, TCE is used in countless commercial, military, and medical industries. TCE exposure is not limited to those in close proximity; it also pollutes the outdoor air, taints groundwater, and contaminates indoor air. It is present in an excess amount of groundwater in the U.S. It evaporates from underlying soil and groundwater and enters home, work, and schools, often undetected. Researchers found that a similar chemical, perchloroethylene (PCE), transforms into TCE. TCE damages parts of cells in the brain, such as the mitochondria.5

A 2023 study compared veterans from Camp Lejeune (where marines were exposed to up to 70 times the EPA recommended level of TCE) to veterans from Camp Pendleton, a similar camp which did not have high levels of TCE.6 They found that the former marines at Camp Lejeune had a significantly higher chance of developing Parkinson’s than their colleagues at Camp Pendleton. Although fewer than 1% of the veterans developed Parkinson’s at either camp, the chance of developing Parkinson’s was 70% higher at Lejeune than it was at Pendleton.

Traumatic Brain Injury and paraquat

A 2012 study concluded that people who reported traumatic brain injury and had exposure to paraquat—a chemical used to kill weeds and other plants—were three times more likely to develop Parkinson’s disease than other people.7 Traumatic brain injury was defined as a loss of consciousness for more than 5 minutes.  The study was based on interviews with 357 Parkinson’s patients and 754 people from the general population in Central California who otherwise matched the Parkinson’s patients. Participants were asked to report if they ever experienced a head injury with a loss of consciousness for more than 5 minutes. Using a tracking system that measures chemicals in the environment, researchers assessed participants’ exposure to paraquat based on where they lived and where they worked between 1974 and 1999. Paraquat is an herbicide that can only be applied by licensed professionals.8 It is not the type of weed killer used in people’s backyards; it is used in farming, which is why the researchers chose the agricultural area of Central California.

For some time, scientists have speculated that a traumatic brain injury might make the brain more vulnerable to certain chemicals in pesticides and herbicides, thereby worsening the effects of exposure to them. The findings of the Central California study suggest that head injury and paraquat exposure combine to damage dopamine-producing cells located in the brain. Dopamine cells enable a person’s motor functions. When these cells are damaged, a person’s motor functions can be permanently impaired. While dopamine cells were damaged by head injury and paraquat exposure alone, more cells were damaged when traumatic brain injury was accompanied by exposure to paraquat.

When Should You Be Concerned?

Has everyone with Parkinson’s been exposed to TCE, had a brain injury, or been exposed to paraquat? No: Parkinson’s happens after brain cells that make dopamine have been damaged.  Damage to brain cells occurs for different reasons in different people. More research is needed on the percentage of Parkinson’s cases that can be explained by the combination of these, or other, factors.

Is There Anything You Can Do to Prevent or Delay Parkinson’s?

While there is no cure for Parkinson’s, there is growing evidence that you can help prevent it as well as slow the worsening of symptoms.

Exercise. Over the years, researchers have reported mixed results about whether physical activity helps prevent the disease. However, a study published in 2023 took a different approach, evaluating physical activity of adults who were approximately 10 years younger than the age when people are usually diagnosed with Parkinson’s.9  They found that the people who were more physically active in their early to mid-adulthood were significantly less likely to develop Parkinson’s compared to their less active colleagues. The researchers pointed out that patients who are eventually diagnosed with the disease start showing some early symptoms (such as a small tremor or constipation) that may discourage them from exercising, which could be why the benefits of exercise weren’t as clear in the past. This study indicates that exercise can lower your risk of developing Parkinson’s, and it is beneficial to keep exercising through your early to mid-adulthood.

Diet. A different 2023 study looked at how diet could affect your chances of developing Parkinson’s and they found that people who followed a Mediterranean diet had a significantly lower risk of developing the disease. A Mediterranean diet consists of eating a lot of fruits, vegetables, low-fat proteins (such as fish or poultry), olive oil, and legumes (such as beans or peas) and has been linked to lower risk of heart disease and stroke. This study suggests that it may also help to lower the chances of developing Parkinson’s compared to people who have other eating habits. In addition, studies conducted in both the US and Europe have found that people who eat or drink more dairy products may be more likely to develop Parkinson’s. 10 However, research is still underway to determine if dairy products are related to Parkinson’s.

Lifestyle. Although the exact causes of Parkinson’s are still being studied, there are several factors that may increase the chances of developing the disease. In small studies, caffeine, Vitamins B and D, and alcohol have all been linked to reducing the chances of developing Parkinson’s, but similar, larger studies had mixed results. In general, research indicates that lowering stress decreases your chances of developing Parkinson’s.11

Treatments

There are some treatments available that may help manage the symptoms of Parkinson’s. The main therapy for Parkinson’s is a drug called levadopa, which is used to help brain cells produce dopamine. The lack of dopamine production in the brain is a primary factor in a Parkinson’s disease diagnosis. Levadopa is taken in combination with another drug, carbidopa, which is used to manage the side effects. These side effects include paralysis and difficulty breathing.12 A single oral dose of levodopa is able to improve motor signs providing benefits on dexterity, ability to walk, and speech for a limited period of time. However, experts do not agree on when levodopa should be started.13

For Parkinson’s patients whose symptoms cannot adequately be treated by medication, researchers are working on other treatment options, including Deep Brain Stimulation (DBS), a surgically implanted medical device that helps control movement and balance for Parkinson’s patients.14 DBS, approved by the Food and Drug Administration in 2002, is designed to block nerve signals that cause tremors, shaking, and other symptoms of Parkinson’s.

Studies show that DBS can curb some symptoms in patients with advanced Parkinson’s, but the treatment also has risks. A 2009 study published in JAMA (the Journal of the American Medical Association), found that by 6 months after surgery, patients receiving DBS had gained, on average, four and a half more hours per day of good symptom control, while patients receiving standard medical care showed no change in symptom control.15 Patients with DBS also had significant improvements in quality of life as compared to patients receiving standard medical care, who had almost no change in quality of life over the six-month study period. On the other hand, the DBS patients experienced many more moderate to severe side effects than the patients receiving standard care, particularly in the first three months. Patients with the surgically implanted device were more likely to fall, have gait disturbances, dyskinesia (problems with controlling movement), motor dysfunction (problems with movement), problems with balance, experience depression, and suffer from dystonia, a disorder which causes muscles to contract uncontrollably and the body to contort. The most common problem for DBS patients (about 10% of patients) was infection at the site of the surgery, requiring antibiotics and sometimes the removal of all or part of the device.

Focused ultrasound is another non-medication treatment. It destroys a small neuron cluster in the brain in order to disrupt the pathway that produces uncontrolled movement and motor impairment. This treatment was approved in 2016 by the Food and Drug Administration for treatment of essential tremor, a common movement disorder that involves an involuntary tremor in both hands and arms when moving and standing still. A March, 2023 small study investigating a version of this method for Parkinson’s patients found that patients receiving this non-invasive treatment experienced an improvement in their symptoms that lasted at least a year or more.16 However, side effects included gait disturbance, loss of taste, visual problems, and facial weakness and this treatment for tremors is considered less effective than DBS.17 With DBS, tissue is not destroyed, but stimulated. DBS is also available for Parkinson’s dyskinesia and motor impairment. However, DBS requires an invasive procedure, making one or more small openings in the skull into which a wire is inserted and guided to the target area in the brain. The wire is then connected to a small neurostimulator implanted in the chest.

The bottom line is that patients considering various treatments for Parkinson’s need to know the risks and decide whether they are worth taking. More research is needed to determine if the benefits of DBS or focused ultrasound truly outweigh the risks for most patients. If only some patients truly benefit, then it is important to know which patients those are likely to be.

All articles are reviewed and approved by Dr, Diana Zuckerman and other senior staff.

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  8. Center for Disease Control. Facts about paraquat. https://emergency.cdc.gov/agent/paraquat/basics/facts.asp
  9. Portugal, B., Artaud, F., Degaey, I., Roze, E., Fournier, A., Severi, G., Canonico, M., Proust-Lima, C., & Elbaz, A. (2023). Association of Physical Activity and Parkinson Disease in Women: Long-term Follow-up of the E3N Cohort Study. Neurology, 10.1212/WNL.0000000000207424. Advance online publication. https://doi.org/10.1212/WNL.000000000020742
  10. Maraki, M. I., Yannakoulia, M., Xiromerisiou, G., Stefanis, L., Charisis, S., Giagkou, N., Kosmidis, M. H., Dardiotis, E., Hadjigeorgiou, G. M., Sakka, P., Scarmeas, N., & Stamelou, M. (2023). Mediterranean diet is associated with a lower probability of prodromal Parkinson’s disease and risk for Parkinson’s disease/dementia with Lewy bodies: A longitudinal study. European journal of neurology, 30(4), 934–942. https://doi.org/10.1111/ene.15698
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