Parkinson’s disease is a brain disorder that causes unintended or uncontrollable movements, such as shaking, stiffness, and difficulty with balance and coordination.
Symptoms usually begin gradually and worsen over time. As the disease progresses, people may have difficulty walking and talking. They may also have mental and behavioral changes, sleep problems, depression, memory difficulties, and fatigue.
While virtually anyone could be at risk for developing Parkinson’s, some research studies suggest this disease affects more men than women. It’s unclear why, but studies are underway to understand factors that may increase a person’s risk. One clear risk is age: Although most people with Parkinson’s first develop the disease after age 60, about 5% to 10% experience onset before the age of 50. Early-onset forms of Parkinson’s are often, but not always, inherited, and some forms have been linked to specific gene mutations.
What causes Parkinson’s disease?
The most prominent signs and symptoms of Parkinson’s disease occur when nerve cells in the basal ganglia, an area of the brain that controls movement, become impaired and/or die. Normally, these nerve cells, or neurons, produce an important brain chemical known as dopamine. When the neurons die or become impaired, they produce less dopamine, which causes the movement problems associated with the disease. Scientists still do not know what causes the neurons to die.
People with Parkinson’s disease also lose the nerve endings that produce norepinephrine, the main chemical messenger of the sympathetic nervous system, which controls many functions of the body, such as heart rate and blood pressure. The loss of norepinephrine might help explain some of the non-movement features of Parkinson’s, such as fatigue, irregular blood pressure, decreased movement of food through the digestive tract, and sudden drop in blood pressure when a person stands up from a sitting or lying position.
Many brain cells of people with Parkinson’s disease contain Lewy bodies, unusual clumps of the protein alpha-synuclein. Scientists are trying to better understand the normal and abnormal functions of alpha-synuclein and its relationship to genetic mutations that impact Parkinson’s and Lewy body dementia.
Some cases of Parkinson’s disease appear to be hereditary, and a few cases can be traced to specific genetic mutations. While genetics is thought to play a role in Parkinson’s, in most cases the disease does not seem to run in families. Many researchers now believe that Parkinson’s results from a combination of genetic and environmental factors, such as exposure to toxins.
Symptoms of Parkinson’s disease
Parkinson’s has four main symptoms:
- Tremor in hands, arms, legs, jaw, or head
- Muscle stiffness, where muscle remains contracted for a long time
- Slowness of movement
- Impaired balance and coordination, sometimes leading to falls
Other symptoms may include:
- Depression and other emotional changes
- Difficulty swallowing, chewing, and speaking
- Urinary problems or constipation
- Skin problems
The symptoms of Parkinson’s and the rate of progression differ among individuals. Early symptoms of this disease are subtle and occur gradually. For example, people may feel mild tremors or have difficulty getting out of a chair. They may notice that they speak too softly, or that their handwriting is slow and looks cramped or small. Friends or family members may be the first to notice changes in someone with early Parkinson’s. They may see that the person’s face lacks expression and animation, or that the person does not move an arm or leg normally.
