Parkinson's disease is a condition that affects the brain, particularly the areas that control movement and balance. It can cause worsening neurological changes that often start with tremors and muscle rigidity. It also increases a person's risk of depression and dementia.
In this article, learn about how genetics affect the development of Parkinson's disease, and when to talk to a doctor about family history and genetic testing.
Genetics and Parkinson's disease
Certain genes that increase the risk of Parkinson's developing may be passed down through family members.
An estimated 15 percent of people with Parkinson's disease have a family history of the condition.
Doctors have identified genes that are passed down from family members that seem to increase a person's likelihood of developing Parkinson's. They have also identified genes where damage or a mutation in the gene increases the risk for a particular condition.
Parkinson's disease causes a lack of dopamine in the brain, which affects movement. Some genes appear to influence the ability of the brain to break down proteins that are present in neurons where dopamine is produced.
Genes associated with Parkinson's disease
Researchers have identified several genes that are thought to be dominant and run in families with a history of Parkinson's disease.
A dominant gene is one that is almost always passed down from parent to child and influences the likelihood that a person will inherit a particular trait or condition.
According to the National Human Genome Research Institute, genes that are associated with Parkinson's disease include:
- SNCA (PARK1)
- UCHL1 (PARK5)
- LRRK2 (PARK8)
There are also recessive genes linked to Parkinson's disease. If a gene is recessive, it means that a parent may carry the gene but not have the characteristic or condition linked to it. Parkinson's disease is one such condition.
When a child inherits a recessive gene from both parents, they may have an increased risk of Parkinson's disease. Examples of these genes include:
- PARK2 (PARK2)
- PARK7 (PARK7)
- PINK1 (PARK6)
Inheriting any of the genes doctors have identified as being related to Parkinson's disease does not necessarily mean a person will develop the condition.
There are other, undiscovered genes and environmental factors that affect the development of Parkinson's.
When should a person get genetic testing?
Genetic testing may not always help to determine whether someone is at risk of developing Parkinson's or not.
While researchers know some of the genes associated with an increased risk of Parkinson's disease, this is not enough to provide meaningful results for most people with a family history of the condition.
One exception is for people diagnosed with Parkinson's disease before 30 years of age.
Researchers have identified the presence of a mutation in the PINK1 gene in about 2 percent of people with early-onset Parkinson's disease.
Genetic testing exists for the PINK1, PARK7, SNCA, and LRRK genes, which may influence Parkinson's disease. A person can talk to their doctor or a genetic counselor to determine if genetic testing may be a good choice for them.
There are several risk factors for Parkinson's disease, including:
- Advancing age. Doctors usually diagnose the disease when a person is 50 years of age or older. While exceptions exist, being older is a risk factor.
- Being male. Doctors diagnose men in greater numbers than women. This does support the theory that Parkinson's has a genetic link.
- Family history. A person is more likely to develop Parkinson's disease if they have a parent or sibling with the disease.
- History of exposure to toxins. People who are exposed to environmental pesticides and herbicides, such as farmers, seem to have an increased risk of Parkinson's disease.
- History of head trauma. An injury to the brain, neck, or upper spine has been associated with greater risk for the disease.
Having one or more of these risk factors does not mean a person will develop Parkinson's, only that they have a higher risk than others in the general population.
Early signs of Parkinson's
Parkinson's disease is a progressive disorder. Symptoms may start with minor changes to movement or thinking and worsen with time.
Early symptoms may include a small tremor or movement in one hand only. Other early symptoms can include:
- problems with balance
- lack of arm swing when walking
- problems creating facial expressions
- speech problems, such as slurring words
- unexplained muscle stiffness
Parkinson's disease often starts to affect one side of the body first. As the disease progresses, it will begin to show on both sides.
A person should always talk to their doctor if they are concerned their symptoms could be related to Parkinson's disease or another condition.
Can Parkinson's disease be prevented?
Sports and exercises that involve balance, including dancing or tai chi, may help to reduce the risk of Parkinson's.
Doctors and researchers have not yet identified a way to prevent Parkinson's disease from developing.
However, some studies have linked exercise with a reduction in Parkinson's disease risk. According to one review, exercises associated with balance have been shown to be particularly effective.
Examples of exercise that involves balance include walking, tai chi, and dancing.
Although researchers have come a long way in terms of knowledge about the causes of Parkinson's disease, there are still many discoveries to be made.
According to one study, the presence of one of the six known gene mutations is detected in only 3 to 5 percent of people who develop Parkinson's disease without a family history. This means there are many other factors that may influence the development of the disease.