How Do People Get Parkinson’s?

  • Medical Reviewer: Dany Paul Baby, MD
Medically Reviewed on 7/25/2022

What is Parkinson’s disease?

Parkinson's disease is a chronic age-related brain condition of the nervous system, causing parts of your brain to degenerate. People get Parkinson's due to genetic and environmental factors, age, gender, and other things.
Parkinson's disease is a chronic age-related brain condition of the nervous system, causing parts of your brain to degenerate. People get Parkinson's due to genetic and environmental factors, age, gender, and other things.

Parkinson’s disease is a chronic age-related brain condition of the nervous system, causing parts of your brain to degenerate.

Parkinson’s disease typically leads to sluggish movements, twitching, and sometimes an inability to balance your body. Although the condition can’t be cured, there are some medicines and treatments that may improve some of the symptoms. Roughly one million people in the U.S. and about ten million worldwide have Parkinson’s Disease.

Symptoms of Parkinson’s disease

Symptoms typically start slowly and continue to deteriorate over time. As the condition worsens, people generally exhibit four symptoms: 

  • Trembling in the limbs and the jaw
  • Tightening of the muscles for a considerable time
  • Sluggish movements
  • Inability to balance the body and a lack of physical coordination that could cause falls

Other challenges people with this condition face are certain mental and physical changes, including  inability to sleep, having difficulty remembering things, and a general feeling of tiredness. In some cases, Parkinson’s can also exhibit other symptoms such as:

  • Skin issues
  • Urinary and constipation issues
  • Difficulty with oral functions like talking, chewing, and swallowing
  • Emotional transformations such as depression

Symptoms usually differ from one person to the next. Many people with Parkinson’s disease have shared that before the onset of symptoms such as tightening of the muscles, they also had other issues such as constipation, lack of sleep, and a loss of their sense of smell.

What causes Parkinson’s disease?

This condition usually affects nerve cells in a tiny part of your brain called the substantia nigra that’s responsible for making dopamine, a neurotransmitter (the brain’s chemical messenger). Dopamine is used to send messages from one nerve cell to another in your brain and from your brain to the rest of your body.

Dopamine plays a critical role in many bodily functions, especially to control muscle movements and in your brain’s pleasure and reward centers. The reward centers are activated when we do something rewarding like finishing an important task or eating food that’s very tasty. It also affects other physiological functions such as:

  • Learning and attention
  • Mood
  • Heart rate
  • Kidney function
  • Blood vessel function
  • Sleep
  • Pain processing
  • Lactation

These nerve cells (also called neurons) in the substantia nigra die as you age. The death leads to a reduction in the production of dopamine, which in turn leads to challenges with the movements that Parkinson’s disease is linked to.

In most cases, this happens slowly but sometimes the loss of cells happens quickly, causing the onset of Parkinson’s disease. You can see the symptoms of this condition when around 50% to 60% of the cells in the substantia nigra are dead.

Parkinson’s disease is also known to affect the nerve endings that are responsible for the production of norepinephrine, another chemical messenger, that controls several bodily functions. This includes essential functions such as your heart rate and blood pressure.

The reduced levels of norepinephrine are linked to non-movement symptoms of Parkinson’s disease such as inconsistent blood pressure, tiredness, and diminished activity in the digestive tract.

Scientists around the world are still trying to figure out why the neurons die. But there’s a general acceptance in the scientific community that these cells die because of a combination of multiple factors that could be genetic or environmental.

Genetic factors that cause Parkinson’s disease

Scientists estimate that genes are the primary cause in less than 10% of the incidences of Parkinson’s disease. The most prevalent genetic cause that triggers Parkinson’s disease is a defect in the gene known as LRRK2.

In this, you either genetically inherit a copy of a mutated gene from one of your parents or you get one copy of mutated genes from each of your parents. The defect in the LRRK2 gene is commonly found in families that have a Jewish or North African descent.

Research also suggests that you’re twice as likely to get Parkinson’s if you have a parent or a sibling who has it.

Environmental factors that cause Parkinson’s disease

The medical fraternity believes that another common reason for the onset of Parkinson’s disease are the environmental factors. These include coming into contact with farming chemicals and pesticides, heavy metals (such as arsenic, cadmium, lead, and mercury), and Agent Orange, a mixture of herbicides that also contains dioxin and was used by the U.S. military in Vietnam.

Dioxin is a dangerous chemical present in many herbicides that were introduced in the 1940s. They are highly toxic and can lead to reproductive and developmental issues, harm the immune system, meddle with your hormones, and also cause cancer. The use of dioxins was discontinued in 1985 by the U.S. Environmental Protection Agency.

Around 2.6 million U.S. military veterans who served in Vietnam between January 1965 and April 1970 could have come in contact with Agent Orange.

It’s difficult to establish a clear connection to an environmental factor since the onset of Parkinson’s disease symptoms would typically be many years after any such contact. But it’s possible that environmental aspects could play a role in the onset of Parkinson’s, especially in people that are genetically vulnerable.

Other risk factors for Parkinson’s disease

Research has found that there are many changes that occur in your brain after the onset of Parkinson’s disease such as the presence of specific substances in the brain. Other biological factors have also been linked to the onset of Parkinson’s.

Lewy bodies

One of the markers of Parkinson’s disease is the presence of Lewy bodies in brain cells. Although Lewy bodies are made up of multiple substances, it’s the presence of a protein called alpha-synuclein that’s specifically linked to this condition.

Alpha-synuclein is present in all Lewy bodies in a clustered form that’s hard to break down. Researchers are studying more about this protein and its effects on brain function.


The average age for the onset of Parkinson’s is 60 years. The older you get, the more likely the chances of getting Parkinson’s.


Men are more likely to get Parkinson’s disease than women.

Contact with toxins

Continued contact with herbicides and pesticides may put you at higher risk of Parkinson's disease.


Parkinson's disease is only seen in people of advanced age. See Answer
Medically Reviewed on 7/25/2022

Cleveland Clinic: "Parkinson's Disease."

Harvard Health Publishing: "Dopamine: The pathway to pleasure."

Johns Hopkins Medicine: "Parkinson's Disease Risk Factors and Causes."

Parkinson Foundation: "Causes."

The American Parkinson Disease Association: "Potential Causes of Parkinson's Disease."

U.S. Department of Health and Human Services: "Parkinson's Disease: Causes, Symptoms, and Treatments."

U.S. Department of Veterans Affairs: "Agent Orange: Parkinson's disease."

U.S. Environmental Protection Agency: "2,4-D," "Learn about Dioxin."