Parkinson’s disease is a movement disorder. It affects the nervous system, and symptoms become worse over time.

Other movement disorders include cerebral palsy, ataxia, and Tourette syndrome. They happen when a change in the nervous system affects a person’s ability to move or stay still.

The National Institutes of Health (NIH) note that, in the United States, around 50,000 people receive a diagnosis of Parkinson’s disease (PD) each year, and around half a million people are living with the condition.

Read on to find out more about this condition, the early signs, and what causes it.

What is Parkinson’s disease?

Tremor in one hand is a early sign
Tremor in one hand is a early sign of Parkinson’s disease.

The symptoms of PD 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 will have dementia.

Most of the symptoms result from a fall in dopamine levels in the brain.

One study, based in France, found in 2015 that men are 50 percent more likely to develop PD than women overall, but the risk for women appears to increase with age.

In most people, symptoms appear at the age of 60 years or over. However in 5–10 percent of cases they appear earlier. When PD develops before the age of 50 years, this is called “early onset” PD.

Early signs

Here are some early signs of PD:

  • Movement: There may be a tremor in the hands.
  • Coordination: A reduced sense of coordination and balance can cause people to drop items they are holding. They may be more likely to fall.
  • Gait: The person’s posture may change, so that they lean forward slightly, as if they were hurrying. They may also develop a shuffling gait.
  • Facial expression: This can become fixed, due to changes in the nerves that control facial muscles.
  • Voice: There may be a tremor in the voice, or the person may speak more softly than before.
  • Handwriting: This may become more cramped and smaller.
  • Sense of smell: A loss of sense of smell can be an early sign.
  • Sleep problems: These are a feature of Parkinson’s, and they may be an early sign. Restless legs may contribute to this.

Other common symptoms include:

  • mood changes, including depression
  • difficulty chewing and swallowing
  • problems with urination
  • constipation
  • skin problems
  • sleep problems

REM sleep disorder: Authors of a study published in 2015 describe another neurological condition, REM sleep disorder, as a “powerful predictor” for PD and some other neurological conditions.

The importance of recognizing early symptoms

Many people think that the early signs of Parkinson’s are normal signs of aging. For this reason, they may not seek help.

However, treatment is more likely to be effective if a person takes it early in the development of PD. For this reason, it is important to get an early diagnosis if possible.

If treatment does not start until the person has clear symptoms, it will not be as effective.

Moreover, a number of other conditions can have similar symptoms.

These include:

  • drug-induced Parkinsonism
  • head trauma
  • encephalitis
  • stroke
  • Lewy body dementia
  • corticobasal degeneration
  • multiple system atrophy
  • progressive supranuclear palsy

The similarity to other conditions can make it hard for doctors to diagnose Parkinson’s disease in the early stages.

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

Causes and risk factors

Scientists are not sure what causes PD. It happens when nerve cells die in the brain.

Parkinson's with Lewy bodies
If a person with Parkinson’s also has changes known as Lewy bodies in the brain, they can develop dementia.

Low dopamine levels: Scientists have linked low or falling levels of dopamine, a neurotransmitter, with PD. This 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. Low dopamine levels can make it harder for people to control their movements.

As dopamine levels fall in a person with PD, their symptoms gradually become more severe.

Low norepinephrine levels: Norepinephrine, another neurotransmitter, is important for controlling many automatic body functions, such as the circulation of the blood.

In PD, the nerve endings that produce this neurotransmitter die. This may explain why people with PD experience not only movement problems but also fatigue, constipation, and orthostatic hypotension, when blood pressure changes on standing up, leading to light-headedness.

Lewy bodies: A person with PD may have clumps of protein in their brain known as Lewy bodies. Lewy body dementia is a different condition, but it has links with PD.

Genetic factors: Sometimes, PD appears to run in families, but it is not always hereditary. Researchers are trying to identify specific genetic factors that may lead to PD, but it appears that not one but a number of factors are responsible.

For this reason, they suspect that a combination for genetic and environmental factors may lead to the condition.

Possible environmental factors could include exposure to toxins, such as pesticides, solvents, metals, and other pollutants.

Autoimmune factors: Scientists reported in JAMA in 2017 that they had found evidence of a possible genetic link between PD and autoimmune conditions, such as rheumatoid arthritis.

In 2018, researchers investigating health records in Taiwan found that people with autoimmune rheumatic diseases (ARD) had a 1.37-higher chance of also having PD than people without ARD.


Pesticides may increase the risk of PD
Using appropriate protection when using pesticides and other toxins may help reduce the risk of PD.

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

Turmeric: This spice contains curcumin, an antioxidant ingredient. It may help to prevent the clumping of a protein involved in Parkinson’s disease, at least one laboratory study has found.

Flavonoids: Consuming another type of antioxidant — flavonoids — may lower the risk of developing Parkinson’s disease, according to research. Flavonoids are present in berries, apples, some vegetables, tea, and red grapes.

Avoiding reheated cooking oils: Scientists have linked toxic chemicals, known as aldehydes, to Parkinson’s, Alzheimer’s and other neurodegenerative diseases, and some cancers.

Heating certain oils — such as sunflower oil — to a certain temperature, and then using them again can cause aldehydes to occur in those oils.

Avoiding toxins: Exposure to herbicides, pesticides, and other toxins may increase the risk of neurological diseases such as PD. People should take precautions when using these types of product, for example, by using protective clothing.


Parkinson’s disease is a lifelong condition that involves neurological changes in the body. These changes can make it harder for a person to function in daily life. However, medications and other types of therapy are available for treating PD and reducing the symptoms.

Current treatment can relieve symptoms, but scientists hope that gene therapy or stem cell therapy will one day be able to do more than this, and restore function that the person has already lost.