Parkinson’s disease overview

Parkinson’s disease is a brain disorder in which certain nerve cells gradually lose function over time, disrupting how the brain sends signals to the body. This condition causes changes in movement, such as slowed movement (bradykinesia), stiffness, and uncontrollable shaking or tremors, while also impacting daily life through sleep and mood changes.

When individuals receive a diagnosis of Parkinson’s disease, family members and caregivers can take comfort in knowing that dedicated support communities exist. Around 90,000 adults 65 years or older receive a Parkinson’s diagnosis every year in the U.S., with risk increasing significantly alongside advancing age.

Parkinson’s represents the second-most common neurological condition after Alzheimer’s disease, affecting more than 10 million people worldwide. It’s typically diagnosed later in life, with only about 6.25% of individuals receiving a diagnosis before age 50. The disease occurs more frequently in men than in women for reasons researchers do not yet fully understand.

While no cure currently exists, a range of medications and supportive therapies help manage symptoms and maintain individual quality of life.

What is Parkinson’s disease?

Parkinson’s disease is a brain disorder in which dopamine-producing nerve cells gradually stop working and die. Dopamine acts as a natural messenger in the brain, helping the body execute smooth, balanced muscle movements.

As dopamine levels fall, communication between brain cells is disrupted, leading to movement problems and various non-movement (nonmotor) symptoms. The exact causes of Parkinson’s disease remain only partially understood, though researchers believe the condition develops from a combination of abnormal protein buildup in brain cells, genetic factors, and prior brain injury.

Symptoms vary considerably between individuals:

• Early signs of Parkinson’s can include loss of smell, sleep disturbances, and changes in posture, gait, or handwriting.
• Core movement (motor) symptoms include slowed movement (bradykinesia), tremors, and balance problems.
• Non-movement symptoms include depression, anxiety, cognitive difficulties, and blood pressure changes.

No single blood test or brain scan exists for diagnosing Parkinson’s. Doctors identify the condition by carefully reviewing medical history, assessing physical movement symptoms, and performing neurological exams while ruling out other conditions. Parkinsonism is a broader term covering several disorders with similar movement symptoms.

Parkinson’s is a progressive disease with symptoms that develop gradually. Medications and supportive therapies can reduce symptom severity, helping individuals maintain daily functioning.

Causes and brain changes in Parkinson’s disease

Understanding the causes of Parkinson’s disease begins with specific changes to dopamine-producing brain cells.

The disease develops when dopamine-producing nerve cells, known as dopaminergic neurons, gradually lose function and die. Dopamine is a neurotransmitter: a chemical messenger that nerve cells use to communicate with each other and the rest of the body. As these cells disappear, dopamine levels drop, leading to a communication breakdown between brain cells that gives rise to classic symptoms.

Scientists continue to study why dopamine-producing cells die off. Leading theories and contributing factors include:

• Lewy bodies: Abnormal clumps of protein build up inside brain cells. In people with Parkinson’s, a protein called alpha-synuclein is the main component of Lewy bodies.
• brain inflammation: Chronic inflammation in the brain, potentially originating from immune system responses in the gut, remains an active area of research. However, researchers are unsure about this possibility and are still working to identify the underlying biological mechanisms involved.
• genetics: In a small number of cases, Parkinson’s is linked to specific gene changes. Roughly 4% of individuals carry a rare genetic difference in a single gene that directly causes the condition. Variants in the GBA1 gene represent the most common genetic risk factors, occurring in up to 10% of patients. Carrying this variation does not guarantee disease development; up to 13% of carriers develop Parkinson’s by age 80.
• environmental risk factors: A history of brain injury and exposure to specific chemicals, such as the industrial solvent trichloroethylene or the herbicide paraquat, increases overall risk.

Early warning signs of Parkinson’s disease

Parkinson’s disease affects everyone differently. The order and severity of symptoms vary considerably, and some early signs of Parkinson’s appear years before familiar movement symptoms develop:

• Sleep disturbances: Insomnia, disrupted sleep, restless legs, and daytime fatigue
• Sensory and handwriting changes: Reduced or absent sense of smell (hyposmia) appearing years early, alongside handwriting that grows noticeably smaller (micrographia)
• Gastrointestinal and urinary issues: Constipation, bowel difficulties, bladder urgency, or frequent nighttime urination
• Mood and energy shifts: Depression, anxiety, persistent sadness, feelings of emotional emptiness, and fatigue, or ongoing physical and mental tiredness not relieved by rest
• Early motor changes: Subtle tremors starting in one hand, slower actions, a shuffling walk, reduced coordination, or muscle stiffness, making fine motor tasks like fastening buttons difficult

Because these signs are subtle and overlap with normal aging, doctors often miss them until primary motor features emerge.

Core motor and nonmotor symptoms

Parkinson’s disease leads to a mix of motor symptoms that affect movement, and nonmotor symptoms that touch nearly every other body system. Motor symptoms are sometimes called “cardinal motor symptoms,” reflecting their important role in Parkinson’s diagnosis.

Cardinal motor symptoms

Motor symptoms play an essential role in establishing a diagnosis. Doctors require the presence of bradykinesia, or abnormally slow movement, alongside at least one other cardinal sign:

• Tremor: Uncontrollable shaking, often beginning at rest in a single hand or limb
• Rigidity: Muscle stiffness and resistance to motion

Some people also develop other motor symptoms. These include blurred vision or trouble looking upward, painful muscle cramps called dystonia, and difficulty maintaining an upright posture, balancing, or walking.

Common nonmotor complications

Beyond movement changes, people with Parkinson’s may experience:

• depression and anxiety
• trouble with cognition and memory
• difficulty sleeping
• trouble swallowing and excess drooling
• constipation and other digestive issues
• orthostatic hypotension (a sudden blood pressure drop when standing, causing lightheadedness or fainting)
• loss of smell
• frequent or urgent urination
• sexual difficulties

How Parkinson’s disease is diagnosed

Process steps for diagnosing Parkinson’s present challenges because no single blood test or brain scan can confirm the condition with absolute certainty. Physicians rely on physical symptoms, medical history, and neurological examinations.

• Diagnostic criteria: Confirming slowed movement (bradykinesia) combined with at least one other characteristic motor symptom (tremor, rigidity, or both). Balance and walking problems generally appear later in disease progression.
• Differential evaluation: Ruling out other health conditions that can cause similar symptoms through clinical assessments.
• Specialized imaging: Recommending MRI or dopamine transporter scans (DaTscan) to evaluate brain structure and function.

Anyone noticing early signs should consult a physician for a thorough medical evaluation.

Types of Parkinson’s disease and parkinsonism

Evaluating Parkinson’s disease types requires distinguishing primary Parkinson’s disease from secondary conditions and related syndromes under the umbrella of parkinsonism.

Primary Parkinson’s disease accounts for approximately 80% of all parkinsonism cases. Subtypes include familial Parkinson’s (linked to genetic family history) and early-onset Parkinson’s (onset occurring before age 50).

A few rarer forms of atypical parkinsonism, sometimes called “Parkinson’s Plus” syndromes, involve Parkinson’s-like symptoms:

• Dementia with Lewy bodies: Memory and cognitive changes emerge earlier than typically seen in primary Parkinson’s.
• Progressive supranuclear palsy: Involves difficulty controlling eye movements (especially downward gaze), a tendency to fall backward, and toxic abnormal buildup of protein tau in the brain, which disrupts normal cell function.
• Corticobasal degeneration: Causes motor symptoms that affect one side of the body noticeably more than the other, alongside tau buildup.
• Multiple system atrophy: Combines motor symptoms with pronounced dysfunction in automatic bodily functions like digestion and sweating.

Secondary parkinsonism is different still from Parkinson’s disease, and from Parkinson’s Plus syndromes. Secondary parkinsonisms may develop as complications of another condition, or from certain forms of exposure:

• certain medications (“drug-induced parkinsonism”)
• reduced blood flow in the brain (“vascular parkinsonism”)
• abnormal pressure around the brain (“normal pressure hydrocephalus”)
• viral infections, such as influenza, West Nile virus, or herpes zoster
• exposure to toxins, such as carbon monoxide
• brain injuries or tumors

Disease progression and life expectancy

The connection between Parkinson’s disease life expectancy and disease progression is complex. While Parkinson’s disease itself is rarely a direct cause of death, advanced stages increase the risk of serious, potentially fatal secondary complications:

• Fall-related traumatic injuries: Worsening balance and sudden drops in blood pressure increase fall risks, leading to fractures or head trauma.
• Severe infections: Swallowing difficulties can cause food or liquid to enter the lungs, causing aspiration pneumonia. Reduced mobility can also lead to pressure ulcers that become infected or trigger sepsis.

Parkinson’s is a progressive disease with symptoms that worsen over time, though the pace varies considerably based on key individual factors:

• Sex: Disease progression tends to advance somewhat faster in men than in women.
• Age at onset: Symptoms often progress more quickly in individuals who are older at the time the condition first appears.
• Symptom profile: People with cognitive difficulties tend to have faster disease progression, whereas those whose dominant symptom is tremor tend to progress more slowly.

Working closely with a healthcare team allows individuals living with Parkinson’s and families to establish a treatment plan tailored to specific needs as the condition evolves.

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Parkinson's News Today is strictly a news and information website about the disease. It does not provide medical advice, diagnosis, or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.