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Is Parkinson’s Genetic Or Environmental

Theories About What Causes Parkinsons

Environmental and genetic causes of Parkinson’s disease | Giselle Petzinger

The cause of Parkinsons disease is still unknown, although there is some evidence for the role of genetics, environmental factors, or a combination of both. It is also possible that there may be more than one cause of the disease. Scientists generally believe that both genetics and environment interact to cause Parkinsons disease in most people who have it.

Currently, there is an enormous amount of research directed at producing more answers about what causes Parkinsons disease and how it might be prevented or cured. When physicians diagnose Parkinsons, they often describe it as idiopathic . This simply means that the cause of the disease is not known.

Advancing Age Is The Leading Risk Factor For Pd But Genetics Brain Injury And Exposure To Toxins May Play A Role Too

by Health Writer

    Parkinsons disease is a neurodegenerative disorder that affects approximately one million people in the U.S., and, to date, there is no cure for it. While effective treatments do exist to help you manage a wide array of PD symptoms, they cannot slow the progression of disease. And its not yet known whether, or how, the disease can be prevented. To solve that mystery, scientists first will have to unravel another riddle: what causes PD and which risks can up your odds for this condition to develop later on. Sharing leading-edge research and expert knowledge, well tell you all we know.

    What Do We Know Now About Environmental Factors And Pd

    In the past two decades, scientists have identified over a dozen environmental factors associated with the risk of developing PD, and for a majority, findings are reasonably consistent across studies . Examples include inverse associations with smoking , coffee drinking , vigorous exercise , ibuprofen use , and plasma urate , as well as positive associations with overall pesticide exposure , use of specific pesticides , and traumatic brain injury . For most of these associations, plausible biological hypotheses have been proposed. However, causal inference for these epidemiological findings has been very difficult. Apart from limited and often inconsistent experimental data, for most of these epidemiological observations, reverse causation is a viable potential explanation – that PD development prior to clinical diagnosis changes lifestyle and behavior rather than the other way around. Possible exceptions are the use of certain pesticides. For example, epidemiological findings on rotenone and paraquat are supported by strong experimental evidence, so much so that these chemicals are being used to generate rodent models for PD therapeutic research . Even for pesticides, there are many important questions unanswered. Therefore, despite its importance and a reasonable accumulation of literature, our understanding of environmental contributions to PD is still in its infancy.

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    Genetics And Parkinsons Disease

    The symptoms of Parkinsons disease appear to occur when the brain is no longer able to produce enough dopamine. Low dopamine levels in the brain can affect movement. It is not yet clear what role genetic factors may play in this process.

    However, experts have identified specific genes in which changes appear to increase the risk of developing Parkinsons disease. The symptoms a person experiences may depend on their specific genetic changes.

    Genetic changes can affect how mitochondria work. Mitochondria are the parts of a cell that produce energy. As they do this, they release byproducts commonly known as free radicals. Free radicals can cause cell damage.

    Usually, cells can counter free radicals, but genetic changes can stop this from happening, and the free radicals can cause damage to dopamine cells.

    Genetic changes can also lead to accumulations of a protein called alpha-synuclein in and around neurons throughout the brain. These accumulations are known as Lewy bodies, and the damage they cause can result in Lewy body dementia, which has links to Parkinsons disease.

    Dopamine-producing nerve cells appear to be particularly susceptible to Lewy bodies, and some people develop both Parkinsons disease and Lewy body dementia.

    Specific gene changes have specific outcomes. For example, SNCA affects the processing of alpha-synuclein, and PRKN impacts how mitochondria work.

    The genetic changes involved in Parkinsons disease can be:

    Referral To A Specialist

    Schematic presentation of neuronal death in Parkinson

    If your GP suspects Parkinson’s disease, you’ll be referred to a specialist.

    This will usually be:

    • a neurologist, a specialist in conditions affecting the brain and nervous system
    • a geriatrician, a specialist in problems affecting elderly people

    The specialist will most likely ask you to perform a number of physical exercises so they can assess whether you have any problems with movement.

    A diagnosis of Parkinson’s disease is likely if you have at least 2 of the 3 following symptoms:

    • shaking or tremor in a part of your body that usually only occurs at rest
    • slowness of movement
    • muscle stiffness

    If your symptoms improve after taking a medication called levodopa, it’s more likely you have Parkinson’s disease.

    Special brain scans, such as a single photon emission computed tomography scan, may also be carried out in some cases to try to rule out other causes of your symptoms.

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    Is Parkinson’s Considered A Hereditary Disease

    Nope, Parkinson’s isn’t considered a hereditary disease in most people. According to the Parkinson’s Foundation, about 90% of people with the disease have no genetic link.

    And while there are some genetic markers for Parkinson’s, they don’t guarantee that a person will get the disease. A genetic mutation is just one of several risk factors for Parkinson’s disease. There may also be lifestyle choices and environmental factors involved in the development of the disease. In fact, most people with Parkinson’s disease aren’t aware of any other family member with the condition, according to the National Human Genome Research Institute .

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    In rare cases, Parkinson’s disease can run in families. When three or more relatives get the diseaseespecially under the age of 50, which is considered early onsetexperts believe members of the family may have a genetic predisposition to Parkinson’s.

    No One Definitive Cause Of Parkinsons

    There are no biomarkers or objective screening tests that indicate one has Parkinsons. That said, medical experts have shown that a constellation of factors are linked to it.

    Parkinsons causes are likely a blend of genetics and environmental or other unknown factors. About 10 to 20 percent of Parkinsons disease cases are linked to a genetic cause, says Ted Dawson, M.D., Ph.D., director of the Institute for Cell Engineering at Johns Hopkins. The types are either autosomal dominant or autosomal recessive .

    But that leaves the majority of Parkinsons cases as idiopathic, which means unknown. We think its probably a combination of environmental exposure to toxins or pesticides and your genetic makeup, says Dawson.

    Age. The biggest risk factor for developing Parkinsons is advancing age. The average age of onset is 60.

    Gender. Men are more likely to develop Parkinsons disease than women.

    Genetics. Individuals with a parent or sibling who is affected have approximately two times the chance of developing Parkinsons. Theres been an enormous amount of new information about genetics and new genes identified over the past 10 or 15 years that have opened up a greater understanding of the disease, says Dawson.

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    Age And Genetic Factors Are Not Everything

    The rate of Parkinsons disease globally has exceeded far faster than the population has aged according to the American Parkinson Disease Association.

    Cases of the disease are up by several multiples over the past decades. From 1990 to 2015, the cases of the disease globally more than doubled, suggesting that there is far more at work. From 2015 to 2040, cases are expected to double once again. This is far higher than the rate of aging in the population.

    Toxic Substances That Have Been Linked To Parkinsons Disease

    Ask the MD: Is Parkinson’s disease genetic?

    There are numerous environmental toxins that researchers have tied to the neurological disorders known as parkinson disease. Here are some that have been linked:

    • Agent Orange This was a chemical defoliant used in Vietnam that is already tied to cancer. While there is no definitive link with Parkinsons, the VA at least believes that there is a possibility that the two are tied.
    • Solvents Some studies have shown a link between Trichloroethylene, a substance contained in many solvents, and Parkinsons.
    • PCBs polychlorinated biphenyls were extensively used in the 1970s. They have been often found in the brains of people who have suffered from Parkinsons.
    • Pesticides and herbicides -substances such as insecticides, pesticides and herbicides contain chemicals that researchers have strongly linked with higher incidences of Parkinsons. One of the leading contributors is considered to be Paraquat. For information on Paraquat Parkinsons lawsuits, look here.

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    When To See A Doctor About Parkinsons

    There isnt one specific test to diagnose Parkinsons disease. Doctors will usually evaluate your symptoms and perform several tests to determine if you have the condition. If you notice the following early warning signs, then you should see a doctor.

    The early warning signs of Parkinsons disease include:

    Faqs: Genetics & Parkinsons

    If I have Parkinson’s disease will my child get it too? Will I inherit Parkinson’s if my parent or grandparent has it?

    Most people with Parkinson’s have no known genetic link. Their children will likely never develop Parkinson’s. There are some known genetic variations that increase the risk of getting Parkinson’s, but most people with these variations do not get Parkinson’s. Like many other diseases, Parkinson’s is a result of a complex interaction between genes and environmental factors.

    In a small number of people , Parkinson’s is inherited and can affect multiple family members. Their children may have a higher risk of developing Parkinson’s. However, there is no guarantee they will develop PD.

    What if my genetic test is positive for a Parkinson’s gene?

    Scientists have identified several genetic mutations that can increase the risk of developing Parkinson’s. If someone tests positive for a mutation in a Parkinson’s gene, it does not necessarily mean they will develop PD. Some people who have mutations in the genes associated with Parkinson’s never develop PD. A person may inherit a hereditary genetic mutation that increases their risk for Parkinson’s however, they may also inherit other genes, be exposed to environmental factors or have lifestyle choices that offset the risk. Genetic testing is currently available for the following genes related to Parkinson’s: GBA, PARK7, SNCA, LRRK2, parkin and PINK1.

    What can I do with my genetic test results?

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    Some Are Calling Parkinsons A Man

    Researchers are rapidly coming to the viewpoint that a large number of Parkinsons cases are tied to toxins. These researchers are even reaching conclusions that environment outranks genetics as a cause of Parkinsons.

    One 2020 book discussed an exhaustive study of 17,000 twin brothers to pinpoint the effects that environment could play. The researchers found that people exposed to certain environmental factors were more than twice as likely to develop Parkinsons.

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    Common Symptoms Of Parkinsons Disease

    Here are some of the early signs and symptoms of Parkinsons disease that you need to be on the lookout for in deciding to see a healthcare professional who can provide medical advice.

    • Rigid muscles
    • Lack of ability to write
    • Slowed movement
    • Low blood pressure

    If you notice these, or other symptoms involving the nervous system, it is time to see a doctor. If you experience a sudden drop in the bodys ability to execute any of these tasks or control movements, it is a sign that something is wrong. Doctors may be able to give medications or other treatments that could improve symptoms.

    Study Links Genetic Environmental Causes Of Parkinson’s

    Scientists at the Whitehead Institute for Biomedical Research have demonstrated one of the first links between genetic and environmental causes of Parkinson’s disease.

    Researchers have long known that Parkinson’s can be caused by faulty genes or environmental factors. But a new study by Whitehead scientists found that a single gene, known as PARK9, protects cells from manganese toxicity and rescues neurons from over-expression of the protein alpha-synuclein. Misfolded alpha-synuclein is the hallmark of the debilitating neurological disorder.

    “This is one of the first connections between Parkinson’s disease genetics and the environment,” says Aaron Gitler, one of the co-authors of a paper published online in the Feb. 1 edition of Nature Genetics.

    Parkinson’s disease is a neurodegenerative disorder characterized by tremors, muscle rigidity, and slowed movements. In the neural cells of Parkinson’s patients’ brains, researchers have noted Lewy bodies, abnormal spheres composed of the protein alpha-synuclein. There is currently no cure for the disease, and current Parkinson’s therapies only address disease symptoms.

    “One of the reasons PARK9 is so interesting is when it’s mutated, it leads to early onset parkinsonism,” says Melissa Geddie, a Lindquist postdoctoral researcher and co-author of the paper.

    “These results suggest that one of the gene’s functions is to protect cells from manganese,” says Gitler.

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    Mutations And Toxins Increase Risk

    When mutated, the LRRK2 protein can worsen problems caused by alpha-synuclein. It is one of the most common genetic causes of Parkinsons. In our clinic, about 2 to 3 percent of patients have LRRK2 mutations, he noted. Those mutations may cause Parkinsons by cranking up sensitivity of the immune system they may increase the magnitude of the response to alpha-synuclein.

    But other factors bear consideration. To study the mechanisms responsible for Parkinsons disease, there is a need for model systems that replicate the effects of environmental toxins, said Standaert. He highlighted research by NIEHS grantee Briana De Miranda, Ph.D., of the University of Pittsburgh. She studies, among other things, how organic solvents may boost susceptibility to Parkinsons disease in individuals with LRRK2 mutations.

    Standaert said the fact that inflammation may cause the disorder to advance more than it otherwise would means that anti-inflammatory drugs could hold promise. We have immunologic treatments for a lot of other diseases, such as inflammatory bowel disease, psoriasis, and multiple sclerosis, Standaert said in an interview. Could we use one of those or something similar in Parkinsons disease to slow its progression?

    Genetics: Insights Into Etiology

    Parkinson’s Disease Etiology | Environmental factors | Genetic factors |

    Improvement in genetic analysis techniques in the 1990s led to the discovery of the first genetic cause of PD: mutations in the SNCA gene encoding -synuclein . At around the same time, -synuclein was found to be the major constituent of LB, the pathological hallmark of PD . Subsequently, multiplications of the SNCA gene have been found to cause PD with penetrance increasing with gene dosage . These discoveries brought -synuclein to center stage in the study of the pathogenesis of PD and led to the hypothesis that during different stages of the disease, -synuclein spreads in a stereotypical way within the nervous system in a prion-like fashion .

    Table 2 Examples of genes associated with PD risk

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    What If I Carry The Gene

    There are ongoing clinical trials testing therapies to treat people who have Parkinson’s and carry certain gene mutations. Proving that it can be important to know which gene mutation you carry. Consult with your doctor when considering a genetic test to determine if you are eligible to participate in gene-based clinical trials.

    The Parkinsons Foundation study, PD GENEration: Mapping the Future of Parkinsons Disease, is the first national study to offer genetic testing and counseling at no cost for those with a confirmed Parkinsons diagnosis. Learn more and enroll at Parkinson.org/PDGENEration.

    *Please note that not all content is available in both languages. If you are interested in receiving Spanish communications, we recommend selecting both” to stay best informed on the Foundation’s work and the latest in PD news.

    What Causes Parkinsons Disease

    Developing Parkinsons disease is not something that often happens on its own. Of course, there are genetic factors that could play a part in this neurological disorder. However, it is a combination of genetic and environmental factors that could lead to this disease.

    In some cases, we have seen recent lawsuits that allege that exposure to certain chemicals has caused Parkinsons disease. Here, we will focus on how people could develop Parkinsons. That could give you an idea of whether you may have a possible lawsuit.

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    Other Causes Of Parkinsonism

    “Parkinsonism” is the umbrella term used to describe the symptoms of tremors, muscle rigidity and slowness of movement.

    Parkinson’s disease is the most common type of parkinsonism, but there are also some rarer types where a specific cause can be identified.

    These include parkinsonism caused by:

    • medication where symptoms develop after taking certain medications, such as some types of antipsychotic medication, and usually improve once the medication is stopped
    • other progressive brain conditions such as progressive supranuclear palsy, multiple systems atrophy and corticobasal degeneration
    • cerebrovascular disease where a series of small strokes cause several parts of the brain to die

    You can read more about parkinsonism on the Parkinson’s UK website.

    Page last reviewed: 30 April 2019 Next review due: 30 April 2022

    Other Relevant Environmental Exposures

    DOC2US

    Although not the focus of this article, the Braak hypothesis also provides strong rationales to systematically examine several other environmental exposures that have not been well studied in the context of PD development such as organic solvents , high temperature cooked meats and heterocyclic amines , respiratory or GI infections and inflammation , and the use of antibiotics and antiviral therapies .

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