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What Causes Parkinsons?

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What causes Parkinson’s disease?

Parkinson’s disease is caused by the damage or loss of nerve cells in a specific part of the brain, called the Substantia Nigra. According to the American Parkinson's Disease Association (APDA), degeneration of these nerve cells disrupts the production of a neurotransmitter called dopamine. This is the chemical messenger dopamine is known to regulate the movement and function of our smooth muscle cells. 


When the nerve cells responsible for producing dopamine become damaged, less dopamine is available in the brain. As a result, the part of the brain that controls coordination and movement does not work as well. In Parkinson's, this nerve cell destruction is slow but progressive – it worsens over time. 


Why do nerve cells start degenerating in Parkinson’s?

There is no singular known cause of Parkinson disorder, a nervous system complication, but many scientists believe a combination of genetic and environmental factors is the cause. So far, several potential risk factors associated with the development of Parkinson’s disease have been identified, and two of the main risk factors involve age and gender.



Parkinson's disease is considered a late-onset disorder, with most people over 50 at their diagnosis. Age is considered the greatest risk factor someone has for developing Parkinson's. Several hypotheses regarding age and Parkinson's disease, like damage to cells over time and changes in our genetic expression, occur naturally with aging. 



Men are approximately 1.5 times more likely to develop Parkinson’s disease than women. 


Genetic factors

An estimated 15% of people with Parkinson’s have a family member with the disorder. While it can be hereditary, most cases occur in people who do not have a family history. It is suspected that genetic mutations in certain specific genes cause hereditary forms of the disease, and such gene mutations may also be sporadic and have no familial component. Dozens of genes have been identified, but the most common are:


LRRK2: Mutations in the LRRK2 gene are the most common genetic mutation found in people with Parkinson’s disease.

GBA: Approximately 5-10% of people with Parkinson’s disease have a mutation in the GBA gene.

SNCA: SNCA is the gene responsible for alpha-synuclein; mutations can result in excess production and build-up of alpha-synuclein, which causes deposits on the brain called Lewy bodies.


Environmental factors 

  • Pesticides: There is a strong link to the development of PD, specifically the herbicide Paraquat
  • Head injury: Specifically traumatic brain injury increases the risk
  • Area of residence: Identified differences in the geographic distribution of PD.
  • Exposure to metals: There is a possible relation



Most cases of Parkinson’s disease are considered idiopathic, meaning that there is no identifiable cause. People with idiopathic Parkinson's disease often have slower but more variable disease progression than those with genetic or environmental causes. 


Potential Protective Factors

While scientists have identified substances that can lead to the disease, they have also discovered factors that appear to limit the development of Parkinson's. 

  • Caffeine
  • Anti-inflammatory drugs
  • Smoking- possible protective factor of nicotine
  • Vitamin D
  • Exercise- increased activity early in life decreases the risk.


Do I have Parkinson’s disease? 

Symptoms of Parkinson's disease are classified into two main categories, motor and non-motor. Often, non-motor symptoms are harder to identify and can be misdiagnosed, especially early in the disease. 


Motor symptoms

Parkinson's typically begins with a resting tremor that goes away with purposeful movement. These tremors begin in the hands and feet and progress along with the limbs. 


Bradykinesia, or slowness of movement, is also a common symptom in those with Parkinson’s. This progressively worsening slowness of movement is associated with a “mask-like” facial expression. 


Over time, joints and the spine become more rigid or tight. The early onset of this rigidity can often be misdiagnosed as arthritis or other joint problems associated with decreased range of motion. As the disease progresses, balance issues will also develop, limiting mobility. 


Non-motor symptoms


Cognitive changes: Someone with Parkinson’s may exhibit problems with thinking, word-finding, and judgment. They can additionally develop depression, fatigue, and sleeping problems like insomnia.


Gastrointestinal issues: Constipation is common in those with Parkinson’s due to the slowing of the digestive system.


Weight loss: Loss of weight commonly occurs in the later stages of the disease.




A diagnosis of Parkinson’s is determined with a thorough clinical evaluation. A doctor specializing in neurology with additional training in movement disorders is best suited to make the diagnosis. They will perform a clinical evaluation, physical examination, and history taking.


There is no specific testing available for Parkinson’s disease, and therefore other movement disorders must be ruled out. If a person with a Parkinson-like disease does not have the presence of Lewy bodies, it may be referred to as Parkinsonism. One similarly presenting disorder is progressive supranuclear palsy (PSP). 


PSP has several common symptoms with Parkinson’s disease, like slow eye movements, loss of balance, and walking difficulty. PSP can be differentiated from Parkinson’s based on key symptoms. Specifically, Parkinson's hallmark tremor is not always present in someone with PSP. Eye movement and speech are typically worse in PSP than in Parkinson's. 



There is no known cure for Parkinson's disease, but treatment options are available to manage symptoms and prolong life. It is possible to maintain a good quality of life with medical advice from a qualified healthcare provider.


Some are treated with dopamine therapies / medications, which supplement dopamine in your brain. Examples of dopaminergic medications that you may be prescribed include levodopa/carbidopa, anticholinergic agents, and dopamine agonists.


Side effects of most dopamine therapies include:

  • Nausea/vomiting
  • Drowsiness
  • Low blood pressure
  • Hallucinations


Deep Brain Stimulation

DBS is a surgical procedure that can ease motor symptoms by sending electrical pulses into the brain through thin metal electrodes. Not everyone is a candidate for DBS. To be considered, you must have had your diagnosis for at least four years, had some benefit from medication, and should not have dementia. 


Helpful resources for people with Parkinson’s disease:

The Parkinson's Foundation offers resources to individuals and their caregivers who have been diagnosed with Parkinson’s disease. They strongly recommend setting goals, establishing healthy habits, and finding a doctor who is an expert in Parkinson’s care. 


Michael J. Fox is a famous American actor diagnosed with Parkinson's disease. As a result, he created the Michael J. Fox Foundation, which has resources for those diagnosed with Parkinson’s, and funds research into potential causes, testing, and treatments.


The American Parkinson's Disease Association is a national institute that offers resources for healthcare, caregivers and information on enrolling in clinical trials. Some people diagnosed with Parkinson's disease may find it helpful to participate in clinical trials, as they can help find the cure!

Robert Fisher

A Nurse Director at a large medical center in Boston, MA, who holds a Master’s in Nursing Leadership and Administration and an MBA in Healthcare Management.

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