Parkinson's disease is a progressive disorder of the nervous system that affects your movement. It develops gradually, sometimes starting with a barely noticeable tremor in just one hand. But while a tremor may be the most well-known sign of Parkinson's disease, the disorder also commonly causes stiffness or slowing of movement.

In the early stages of Parkinson's disease, your face may show little or no expression or your arms may not swing when you walk. Your speech may become soft or slurred. Parkinson’s disease symptoms worsen as your condition progresses over time.

Although Parkinson's disease can't be cured, medications may markedly improve your symptoms. In occasional cases, your doctor may suggest surgery to regulate certain regions of your brain and improve your symptoms.

In Parkinson's disease, certain nerve cells (neurons) in the brain gradually break down or die. Many of the symptoms are due to the loss of neurons that produce a chemical messenger in your brain called dopamine. When dopamine levels decrease, it causes abnormal brain activity, leading to signs of Parkinson's disease.

The cause of Parkinson's disease is unknown, but several factors appear to play a role, including:

Your genes: Researchers have identified specific genetic mutations that can cause Parkinson's disease, but these are uncommon except in rare cases with many family members affected by Parkinson's disease. However, certain gene variations appear to increase the risk of Parkinson's disease but with a relatively small risk of Parkinson's disease for each of these genetic markers.
Environmental triggers: Exposure to certain toxins or environmental factors may increase the risk of later Parkinson's disease, but the risk is relatively small.

In summary, more research needs to be done to identify the factors causing Parkinson's disease.

Parkinson's disease symptoms and signs may vary from person to person. Early signs may be mild and may go unnoticed. Symptoms often begin on one side of your body and usually remain worse on that side, even after symptoms begin to affect both sides.

Parkinson's signs and symptoms may include:

Tremor: Your tremor, or shaking, usually begins in a limb, often your hand or fingers. You may notice a back-and-forth rubbing of your thumb and forefinger known as a pill-rolling tremor. One characteristic of Parkinson's disease is a tremor of your hand when it is relaxed (at rest).
Slowed movement (bradykinesia): Over time, Parkinson's disease may reduce your ability to move and slow your movement, making simple tasks difficult and time-consuming. Your steps may become shorter when you walk, or you may find it difficult to get out of a chair. Also, you may drag your feet as you try to walk, making it difficult to move.
Rigid muscles: Muscle stiffness may occur in any part of your body. The stiff muscles can limit your range of motion and cause you pain.
Impaired posture and balance: Your posture may become stooped, or you may have balance problems as a result of Parkinson's disease.
Loss of automatic movements: In Parkinson's disease, you may have a decreased ability to perform unconscious movements, including blinking, smiling or swinging your arms when you walk. You may no longer gesture when talking.
Speech changes: You may have speech problems as a result of Parkinson's disease. You may speak softly, quickly, slur or hesitate before talking. Your speech may be more of a monotone rather than with the usual inflexions. A speech-language pathologist may help improve your speech problems.
Writing changes: Writing may appear small and become difficult.

Medications may greatly reduce many of these symptoms. These medications increase or substitute for dopamine, a specific signalling chemical (neurotransmitter) in your brain. People with Parkinson's disease have low brain dopamine concentrations.

Risk factors for Parkinson's disease include:

Age: Young adults rarely experience Parkinson's disease. It ordinarily begins in middle or late life, and the risk increases with age. People usually develop the disease around age 60 or older.
Heredity: Having a close relative with Parkinson's disease increases the chances that you'll develop the disease. However, your risks are still small unless you have many relatives in your family with Parkinson's disease.
Sex: Men are more likely to develop Parkinson's disease than are women.
Exposure to toxins: Ongoing exposure to herbicides and pesticides may put you at a slightly increased risk of Parkinson's disease.

Parkinson's disease is often accompanied by these additional problems, which may be treatable:

Thinking difficulties: You may experience cognitive problems (dementia) and thinking difficulties, which usually occur in the later stages of Parkinson's disease. Such cognitive problems aren't very responsive to medications.
Depression and emotional changes: People with Parkinson's disease may experience depression. Receiving treatment for depression can make it easier to handle the other challenges of Parkinson's disease.

You may also experience other emotional changes, such as fear, anxiety or loss of motivation. Doctors may give you medications to treat these symptoms.

Swallowing problems: You may develop difficulties with swallowing as your condition progresses. In typical Parkinson's disease, this is rarely a severe problem. Saliva may accumulate in your mouth due to slowed swallow, leading to drooling. Sleep problems and sleep disorders. People with Parkinson's disease often have sleep problems, including waking up frequently throughout the night, waking up early or falling asleep during the day. People may also experience rapid eye movement sleep behaviour disorder, which involves acting out your dreams. Medications may help your sleep problems.
Bladder problems: Parkinson's disease may cause bladder problems, including being unable to control urine or having difficulty urinating.
Constipation: Many people with Parkinson's disease develop constipation, mainly due to a slower digestive tract.

You may also experience:

Blood pressure changes: You may feel dizzy or lightheaded when you stand due to a sudden drop in blood pressure (orthostatic hypotension).
Smell dysfunction: You may experience problems with your sense of smell. You may have difficulty identifying certain odours or the difference between odours.
Fatigue: Many people with Parkinson's disease lose energy and experience fatigue, and the cause isn't always known.
Pain: Many people with Parkinson's disease experience pain, either in specific areas of their bodies or throughout their bodies.
Sexual dysfunction: Some people with Parkinson's disease notice a decrease in sexual desire or performance.

See your doctor if you have any of the symptoms associated with Parkinson's disease — not only to diagnose your condition but also to rule out other causes for your symptoms.

If you've received a diagnosis of Parkinson's disease, you'll need to work closely with your doctor to find a treatment plan that offers you the greatest relief from symptoms with the fewest side effects. Certain lifestyle changes may also help make living with Parkinson's disease easier.

Healthy eating

Eat a nutritionally balanced diet that contains plenty of fruits, vegetables and whole grains. Eating foods high in fiber and drinking an adequate amount of fluids can help prevent constipation that is common in Parkinson's disease.

A balanced diet also provides nutrients, such as omega-3 fatty acids, that may be beneficial for people with Parkinson's disease.

Exercise

Exercising may increase your muscle strength, flexibility and balance. Exercise can also improve your well-being and reduce depression or anxiety.

Your doctor may suggest you work with a physical therapist to learn an exercise program that works for you. You may also try exercises such as walking, swimming, dancing, water aerobics or stretching.

Parkinson's disease can disturb your sense of balance, making it difficult to walk with a normal gait. Exercise may improve your balance. These suggestions may also help:

Try not to move too quickly.

Aim for your heel to strike the floor first when you're walking.

If you notice yourself shuffling, stop and check your posture. It's best to stand up straight.

Look in front of you, not directly down, while walking.

Avoiding falls

In the later stages of the disease, you may fall more easily. In fact, you may be thrown off balance by just a small push or bump. The following suggestions may help:

Make a U-turn instead of pivoting your body over your feet.

Keep your centre of gravity over your feet without leaning or reaching.

Avoid carrying things while you walk.

Avoid walking backwards.

Daily living activities

Daily living activities — such as dressing, eating, bathing and writing — can be difficult for people with Parkinson's disease. An occupational therapist can show you techniques that make daily life easier.