What Is Parkinson’s Disease? Symptoms and Causes

Parkinson’s disease is a brain disorder that can cause involuntary movements like shaking, stiffness, and difficulties with balance and coordination. These symptoms usually start gradually and worsen over time. As the disease progresses, it may also affect walking, talking, and mental functions such as memory, sleep, and mood.1

While anyone can be at risk, research suggests that Parkinson’s disease may affect more men than women, and age is a known risk factor, with most cases occurring after the age of 60.1 However, about 5 to 10 percent of cases occur before the age of 50, and some forms of early-onset Parkinson’s may be inherited, with specific genetic changes linked to the disease.2

Symptoms and Signs of Parkinson’s Disease

Parkinson’s disease occurs when certain nerve cells in the brain that produce dopamine, a chemical messenger that helps control movement, become damaged or die. As a result, people with Parkinson’s disease experience a range of physical and non-physical symptoms that can affect their daily lives.

Parkinson’s disease primarily affects movement control, and its symptoms can vary from person to person. The most common signs and symptoms of Parkinson’s disease include:

Tremors (Shaking)

One of the most obvious signs of Parkinson’s disease is uncontrollable shaking, which often starts in the hands or fingers. When the person is still, these shakes may worsen, but they usually go away or decrease during movements.1,2


Another common sign of Parkinson’s disease is slow movement known as bradykinesia. This may lead to difficulty initiating movements, such as starting to walk or getting up from a chair, or a general reduction in the speed of movements.1,2


Muscle stiffness or rigidity, which makes it hard to move or bend joints, is another common sign of Parkinson’s disease. Different parts of the body can be affected by this stiffness, which can cause discomfort or pain.1,2

Postural Instability

Parkinson’s disease can also cause issues with balance and coordination, which can make it difficult to stay balanced and increase the likelihood of falling.1,2

Other Symptoms

Parkinson’s disease can also cause symptoms that aren’t related to movements, such as anxiety, depression, difficulty falling asleep, constipation, loss of smell, changes in speech, and cognitive changes.3

Stages of Parkinson’s Disease

Parkinson’s disease progresses in stages, and the symptoms may worsen over time. The stages of Parkinson’s disease are:

Stage 1 Parkinson’s

In the beginning, a person may have only mild symptoms that affect only one side of their body. They might have shaking (tremors) and changes in the way they hold themselves or their facial expressions.4

Stage 2 Parkinson’s

As the condition progresses, the symptoms may get worse, and both sides of the body may be affected. It might become harder to do everyday things, and there could be more pronounced shaking (tremors), stiffness (rigidity), and slower movement (bradykinesia).4

Stage 3 Parkinson’s

In stage 3, the symptoms further worsen, and the affected person may experience a significant impact on their daily activities. Impaired balance and coordination may become apparent, and falls may become more frequent. The person may require assistance with certain activities and may need to rely on mobility aids such as a cane or walker.4

Stage 4 Parkinson’s

In stage 4 of Parkinson’s disease, the symptoms become more severe and disabling. An individual with this stage of Parkinson’s may require significant assistance with daily activities such as getting dressed, bathing, and eating. They may have difficulty walking and moving around, and they may require the use of a wheelchair or other mobility aids.4

Muscle rigidity and stiffness may also become more severe, making it challenging for the person to initiate movements. Tremors may persist, but they may be less pronounced than in previous stages.

In addition to physical symptoms, the person may also experience non-motor symptoms such as depression, anxiety, and cognitive changes. These symptoms can make it challenging to manage the disease and maintain independence.

Stage 5 Parkinson’s

In stage 5 of Parkinson’s disease, the symptoms are the most severe and can be very challenging for both the person with Parkinson’s and their caregivers. The person may be unable to stand or walk and may require round-the-clock care.

Severe motor symptoms may be present, such as extreme muscle rigidity, tremors, and difficulty initiating movements. The person may also experience non-motor symptoms such as depression, anxiety, hallucinations, and cognitive changes. These symptoms can make it challenging to communicate, maintain relationships, and carry out daily activities.4

Causes of Parkinson’s Disease

Parkinson’s disease is a complex condition, and the exact cause is still not entirely understood. However, scientists believe that it may be caused by a combination of genetic and environmental factors.

Genetic Factors

There are certain genetic mutations that have been linked to Parkinson’s disease. These mutations can be inherited from a person’s parents and may increase their risk of developing the disease. However, it’s important to note that not all individuals with these genetic mutations will develop Parkinson’s disease.5

Environmental Factors

Exposure to certain environmental toxins may also increase a person’s risk of developing Parkinson’s disease. For example, exposure to pesticides and other chemicals has been linked to an increased risk of the disease.

Additionally, head injuries and traumatic brain injuries may increase a person’s risk. However, more research is needed to fully understand the relationship between environmental factors and Parkinson’s disease.5

Protein Accumulation

In Parkinson’s disease, abnormal protein accumulation, particularly a protein called alpha-synuclein, has been observed in the brain. These protein clumps, known as Lewy bodies, disrupt normal brain function and contribute to the development of Parkinson’s disease.5

Other Factors

Age is another factor that may increase a person’s risk of developing Parkinson’s disease. The disease is more common in individuals over the age of 60. Additionally, certain medications and medical conditions may increase the risk of developing Parkinson’s disease by causing a neurotransmitter (brain chemical) imbalance in the brain.5

Diagnosis and Testing for Parkinson’s Disease

The diagnosis of Parkinson’s disease involves a thorough evaluation by a healthcare provider, including a physical examination and a review of the person’s medical history and symptoms.

During the physical examination, the healthcare provider will look for symptoms such as tremors, muscle rigidity, and difficulty with balance and coordination. They may also ask the person to perform simple movements to assess their motor function.6

There is no single test that can definitively diagnose Parkinson’s disease. Instead, the diagnosis is typically based on the presence of specific symptoms and a process of elimination of other conditions that may cause similar symptoms.

Currently, the following techniques are used by healthcare providers to diagnose Parkinson’s disease:

Imaging Studies

Imaging techniques such as magnetic resonance imaging (MRI) or computed tomography (CT) scans may be used to rule out other causes of the symptoms and to visualize the brain for any abnormalities. Additionally, a dopamine transporter (DAT) scan may be used to assess the function of dopamine-producing neurons in the brain, which are typically affected in Parkinson’s disease.6

Clinical Evaluation

The diagnosis of Parkinson’s disease typically involves a clinical evaluation by a qualified healthcare professional, such as a neurologist. This evaluation is crucial in determining whether a person has Parkinson’s disease and in developing an appropriate treatment plan.

During the clinical evaluation, the healthcare professional will conduct a thorough neurological examination, which may include assessing a person’s motor skills, balance, coordination, reflexes, and other neurological functions. They may also ask the person about their medical history and any medications they are currently taking.7

Blood Tests

In addition to the clinical evaluation and imaging tests, blood tests may also be performed to help diagnose Parkinson’s disease. These tests are used to rule out other conditions that can mimic Parkinson’s disease and to identify any underlying health issues that may contribute to the symptoms.

For example, blood tests may be used to check for thyroid dysfunction or vitamin B12 deficiency, which can cause symptoms similar to those of Parkinson’s disease. Blood tests can also be used to measure the levels of certain proteins, such as alpha-synuclein, that are associated with Parkinson’s disease.6

While blood tests alone cannot definitively diagnose Parkinson’s disease, they can provide valuable information that helps healthcare professionals make an accurate diagnosis. By ruling out other conditions that may cause similar symptoms, blood tests can help ensure that the correct diagnosis is made and that appropriate treatment is provided.

Complications Associated with Parkinson’s Disease

Parkinson’s disease can also cause a range of other complications that can have a significant impact on a person’s quality of life, including non-physical symptoms. Here are some of the most common complications:

Depression and Anxiety

Many people with Parkinson’s disease experience symptoms of depression and anxiety, which can be caused by changes in the brain that affect mood regulation.8

Sleep Problems

Parkinson’s disease can cause disruptions in sleep, including insomnia, restless legs syndrome, and sleep apnea (a condition that disrupts sleep by causing intermittent pauses in breathing, which can have serious consequences if left untreated).8

Cognitive Changes

In some cases, Parkinson’s disease can cause cognitive changes, including difficulty with memory, attention, and problem-solving.8

Swallowing Difficulties

Parkinson’s disease can cause problems with swallowing, which can lead to choking or aspiration pneumonia (a condition where food, liquids, or other substances are inhaled into the lungs instead of being swallowed, leading to inflammation and infection in the lungs).8


Parkinson’s disease can cause digestive problems, including constipation, which can be caused by a slowdown in the movement of food through the digestive tract.8

Urinary Issues

Parkinson’s disease can also cause urinary problems, including incontinence (urinary incontinence is a loss of bladder control) and urinary tract infections.8

Hallucinations and Delusions

In some cases, Parkinson’s disease can cause hallucinations and delusions, which can be caused by changes in the brain that affect perception.8

Medication Side Effects

The medications used to treat Parkinson’s disease can cause a range of side effects, including nausea, vomiting, dizziness, and confusion.

Risk Factors Associated with Parkinson’s Disease

While the exact cause of Parkinson’s disease is unknown, certain factors may increase the risk of developing the condition.10 These risk factors include:

Age: Parkinson’s disease is more commonly diagnosed in people over the age of 60, although it can occur at a younger age as well.

Gender: Men are slightly more prone to developing Parkinson’s disease compared to women.

Family history: Having a family history of Parkinson’s disease increases the risk of developing the condition, although it is not directly inherited in most cases.

Environmental factors: Exposure to certain environmental toxins, such as pesticides and herbicides, has been associated with an increased risk of Parkinson’s disease.

Genetic mutations: Some specific genetic mutations have been identified as risk factors for Parkinson’s disease, although they are relatively rare and account for a small percentage of cases.

Parkinson’s Disease Statistics

  • According to the Parkinson’s Foundation,11 approximately 1.2 million people in the United States are living with Parkinson’s disease, and about 90,000 new cases are diagnosed each year.
  • There are over 10 million individuals worldwide who have been diagnosed with Parkinson’s disease.
  • The likelihood of Parkinson’s disease is 1.5 times higher in men than in women.
  • The risk of developing Parkinson’s disease increases with age, with the majority of cases diagnosed in people over the age of 60.

Resources for Parkinson’s Disease

  • Parkinson’s Foundation: This is a leading organization dedicated to providing information, resources, and support for people living with Parkinson’s disease and their caregivers. They offer a wide range of educational materials, support groups, and programs to help individuals manage their conditions.
  • National Institute of Neurological Disorders and Stroke (NINDS): NINDS is a part of the National Institutes of Health (NIH) and provides up-to-date information on Parkinson’s disease, including research, treatment options, and clinical trials.
  • Movement Disorder Society: This is an international organization focused on advancing research and treatment for movement disorders, including Parkinson’s disease. They provide resources for healthcare professionals and patients.

FAQ About Parkinson’s Disease

Is Parkinson’s disease hereditary?

While Parkinson’s disease is not typically inherited, having a family history of the condition can increase the risk of developing it. Only a small percentage of Parkinson’s cases are directly caused by genetic mutations.

How does Parkinson’s disease progress?

The progression of Parkinson’s disease can vary from person to person, but it typically gets worse over time. As the disease progresses, symptoms can become more severe and may include difficulty walking or talking, dementia, and other complications.

Can Parkinson’s disease affect younger people?

Although Parkinson’s disease is more commonly diagnosed in older adults, it can affect people of any age, including young adults and even children.

How long can someone live with Parkinson’s disease?

The life expectancy for people with Parkinson’s disease is similar to that of the general population, but it can vary depending on factors such as the severity of the disease and the presence of other health conditions.

Can Parkinson’s disease cause dementia?

In some cases, Parkinson’s disease can cause dementia, which is a decline in cognitive function that affects memory, thinking, and behavior. However, not all people with Parkinson’s disease will develop dementia.