A complete guide to Parkinson’s disease

April is Parkinson’s Awareness Month, so it’s a good time to share important information about this brain disorder that affects about one million people in the United States.

Parkinson’s disease (PD) is a disorder of the brain and nervous system that affects the body’s movement. It’s caused by a gradual breakdown of nerve cells in the brain that produce a chemical called dopamine, which helps the brain function. Parkinson’s is a slow but progressive disease, which means that symptoms get worse over time and eventually interfere with walking, talking, and other daily activities.

By the numbers

  • After Alzheimer’s disease, PD is the second most common neurodegenerative disease (a breakdown of the nervous system, especially nerve cells in the brain).
  • Nearly 90,000 Americans are diagnosed with PD each year.
  • More than 10 million people worldwide are living with PD.
  • The risk of developing PD increases with age, but an estimated 4% of people with PD are diagnosed before age 50.
  • Men are 1.5 times more likely to have PD than women.

Signs and symptoms

Common early signs include slowed movement, stiffness, changes in how a person walks, and tremors. Some signs may occur 10-15 years before diagnosis, such as a reduced sense of smell, sleep disorders, mood changes such as depression and anxiety, and constipation.

Symptoms often begin on one side of the body or sometimes in one limb on one side of the body. PD will eventually affect both sides of the body, but symptoms may still be more severe on one side or the other. These symptoms, and how quickly they get worse, can vary from person to person. Early symptoms may not be noticeable to people with PD, so their friends or family members often see the changes first.

There are four main symptoms of PD:

  • Tremors (shaking) in the hands, arms, legs, jaw, or head
  • Muscle stiffness
  • Slowed movement
  • Loss of balance and coordination, sometimes leading to falls

Other symptoms may include:

  • Depression and other emotional or mood changes
  • Difficulty swallowing, chewing, and speaking
  • Urinary problems or constipation
  • Skin problems

Some people with PD may experience problems with memory, attention, and the ability to plan and accomplish tasks. Stress, depression, and some medications also may contribute to these changes. As the disease progresses, some people may develop dementia and be diagnosed with a condition called Parkinson’s dementia. People with Parkinson’s dementia may have severe memory and thinking problems that affect daily living.

Click here to see a list of 10 early signs of PD, from the Parkinson’s Foundation.


Most signs and symptoms of PD begin showing when nerve cells (neurons) in the area of the brain that controls movement become weak and/or die. These neurons normally produce an important brain chemical called dopamine, but when weakened neurons produce less dopamine, movement problems begin.

People with Parkinson’s disease also lose the nerve endings that produce norepinephrine, a chemical that sends messages in the nervous system to control many automatic functions of the body, such as heart rate and blood pressure. The loss of norepinephrine might help explain some PD symptoms not related to movement, such as tiredness and irregular blood pressure.

Medical researchers are still looking for the causes of PD. Some cases of PD appear to be inherited (passed down from family members), and a few cases can be traced to variations in certain genes. While genes are thought to play a role in PD, the disease does not seem to run in families in most cases. Many researchers now believe that PD is caused by a combination of genetic and environmental factors, such as exposure to toxins.


Doctors usually diagnose the disease by taking a person’s medical history and performing a neurological examination. If symptoms improve after a patient starts taking certain medications for PD, then the patient may be diagnosed with PD.

Until recently, there were no blood or laboratory tests to diagnose non-genetic cases of PD. In April 2023, researchers discovered a new way to detect PD by identifying a “biomarker” for the condition. Short for biological marker, a biomarker is a measure that captures information about cells and organisms.

Many biomarkers come from simple measurements made during routine doctor visits, like blood pressure or body weight, and they can serve as early warning systems for health risks. The biomarker for PD is the presence of abnormal alpha-synuclein, also known as the “Parkinson’s protein,” in brain and body cells. This new method can find the biomarker in people with PD as well as those who haven’t yet been diagnosed or begun showing symptoms but are at a high risk of developing it.

Certain medical conditions can cause symptoms similar to those of PD. People with PD-like symptoms due to other causes are sometimes said to have “parkinsonism”. These conditions may be misdiagnosed as PD at first, but certain medical tests and responses to drug treatment can help rule out PD. Many other diseases have similar symptoms but require different treatments, so it’s important to get an accurate diagnosis as soon as possible.


There is no cure for PD, but certain medications, surgical treatments, and other therapies may reduce some symptoms. Medications can help treat PD symptoms by:

  • Increasing the level of dopamine in the brain
  • Having an effect on other brain chemicals that transfer information among brain cells
  • Helping control symptoms not related to movement

A drug called levodopa is the main medication used to treat PD. Nerve cells use levodopa to make dopamine to replace the brain’s reduced supply.

For people with PD who do not respond well to medications, doctors may recommend deep brain stimulation. With this therapy, electrodes are implanted into part of the brain and connected to a small electrical device placed in the chest. This stimulates areas in the brain that control movement to help stop many of the movement-related symptoms of PD.


Although the progression of PD is usually slow, a person’s daily routines eventually may be affected. Activities such as working, taking care of a home, and socializing with friends may become challenging. The American Parkinson Disease Association (APDA) offers a free, downloadable handbook for people with PD and their family.

The ADPA also provides a guide describing 10 steps that people with PD can take right now to cope with symptoms and the progression of the disease. Click here to see “Living Well with Parkinson’s Disease”.

The changes that PD brings to everyday life can be difficult, but support groups can provide information, advice, and connections to resources for those living with PD and their family and caregivers. The organizations listed below can help people find local support groups and other resources in their communities.

Parkinson Association of Alabama



American Parkinson Disease Association (APDA)

Michael J. Fox Foundation for Parkinson’s Research

Parkinson’s Foundation

The UAB Comprehensive Parkinson Disease and Movement Disorders Clinic specializes in neurological disorders that affect movement, including Parkinson’s disease and similar conditions. Click here to learn more about treatments and new medications, clinical research trials, and the latest advances.

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