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Parkinson’s disease is a movement disorder that affects the nervous system. Its symptoms occur because of low dopamine levels in the brain.

Experts do not know why Parkinson’s disease develops, but they currently believe that genetic changes and exposure to environmental factors, such as toxins, play a key role.

Read on to find out more about the early signs of Parkinson’s disease and what causes it.


The symptoms of Parkinson’s disease develop gradually. They often start with a slight tremor in one hand and a feeling of stiffness in the body. Over time, other symptoms develop, and some people can experience dementia.

Some early signs of Parkinson’s disease may include:

Movement symptoms may start on one side of the body and gradually affect both sides.

Other common symptoms include:

Having these symptoms does not mean a person has Parkinson’s disease. Various other conditions can have similar symptoms, such as:

There is currently no test for Parkinson’s disease. Its similarity to other conditions can make it hard to diagnose in the early stages.


Parkinson’s disease is a neurological disorder that develops when changes occur in the brain. Precisely why it happens is unclear, but scientists have identified some variations that occur.

Low dopamine levels

Parkinson’s disease symptoms mainly result from low or falling levels of dopamine, a neurotransmitter. It happens when cells that produce dopamine die in the brain.

Dopamine plays a role in sending messages to the part of the brain that controls movement and coordination. Therefore, low dopamine levels can make it harder for people to control their movement.

As dopamine levels continue to fall, symptoms gradually become more severe.

Low norepinephrine levels

Parkinson’s disease may also involve damage to the nerve endings that produce another neurotransmitter, norepinephrine, which contributes to blood circulation and other automatic body functions.

Low levels of norepinephrine in Parkinson’s disease may increase the risk of both motor and nonmotor symptoms, such as:

This may explain why people with Parkinson’s disease commonly experience orthostatic hypotension. This refers to when a person’s blood pressure changes when they stand up, leading to lightheadedness and a risk of falling.

Lewy bodies

A person with Parkinson’s disease may have clumps of protein known as alpha-synuclein, or Lewy bodies, in their brain.

The accumulation of Lewy bodies can cause a loss of nerve cells, leading to changes in movement, thinking, behavior, and mood. It can also lead to dementia.

Lewy body dementia is not the same as Parkinson’s disease, but people may have both as the symptoms are similar.

Genetic factors

Experts have identified changes in several genes that appear to have links with Parkinson’s disease, but they do not consider it a hereditary condition.

Genetic factors appear to cause only 10% of cases, mostly among people with early onset disease.

Autoimmune factors

In a 2017 study, scientists found a possible genetic link between Parkinson’s disease and autoimmune conditions, such as rheumatoid arthritis.

In 2018, researchers investigating health records in Taiwan found that people with autoimmune rheumatic diseases had a 1.37-higher chance of also having Parkinson’s disease.

Risk factors

Several environmental factors may increase the risk of developing Parkinson’s disease.

These include:

Symptoms usually appear from the age of 60 years. However, 5–10% of people with the disease have early onset Parkinson’s, which starts before the age of 50 years.

Do racial factors affect the risk?

In the past, statistics have suggested that Parkinson’s disease is less likely to affect Black people than other people of other ethnicities in the United States.

However, experts now say this may be due to a lack of awareness about how the disease can affect Black individuals and a higher chance of misdiagnosis due to inequities in health provision.

For more on issues of health equity, see our dedicated hub.


It is not possible to prevent Parkinson’s disease, but some lifelong habits may help reduce the risk.

Avoiding toxins

People should take precautions when using potentially toxic chemicals, such as herbicides, pesticides, and solvents.

Where possible, individuals should take the following steps:

Avoid head trauma

For protection from a traumatic brain injury, people can take the following steps:


Regular physical exercise may help prevent or treat Parkinson’s disease, according to a 20108 study . The authors note that physical activity can help maintain dopamine levels in the brain.

Dietary factors

Some dietary choices may also help reduce the risk of Parkinson’s and other diseases. Research has shown that the following may help:


Parkinson’s disease is a lifelong condition involving neurological changes in the body.

Experts do not know why Parkinson’s disease occurs, but genetic and environmental factors may play a role. Specifically, experts have found strong links with past traumatic brain injury and exposure to toxins.

Exercise, a healthy diet, and avoiding toxins may all help prevent Parkinson’s disease, but there is no current evidence to confirm the specific cause.

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