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What Are The Environmental Causes Of Parkinson Disease

Other Relevant Environmental Exposures

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

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 .

The Search For Environmental Causes Of Parkinsons Disease: Moving Forward

Issue title: The Times They Are a-Changin: Parkinsons Disease 20 Years from Now

Guest editors: Patrik Brundin, J. William Langston and Bastiaan R. Bloem

Article type: Review Article

Authors: Chen, Hongleia * | Ritz, Beateb

Affiliations: Department of Epidemiology and Biostatistics, College of Human Medicine, Michigan State University, East Lansing, MI, USA | Department of Epidemiology and Environmental Health Sciences, Fielding School of Public Health, University of California Los Angeles, Los Angeles, CA, USA

Correspondence: Correspondence to: Honglei Chen, MD, PhD, Department of Epidemiology and Biostatistics, College of Human Medicine, Michigan State University, 909 Wilson Rd, East Lansing, MI 48824, USA. Tel.: +1 517 884 3990 E-mail: .

Keywords: Parkinsons disease, etiology, progression, environmental risk factors, prodromal symptoms

DOI: 10.3233/JPD-181493

Journal: Journal of Parkinson’s Disease, vol. 8, no. s1, pp. S9-S17, 2018


How You Lose Dopamine Production

Damaged nerve cells can be what results in a decreased ability of the brain to create dopamine. Generally, some kind of degradation of the brain cells will reduce dopamine production.

There is some genetic link to parkinsons disease. For example, specific genetic mutations can impact the dopamine production. Far more common is that exposure to something in the environment can impact the brain.

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Better Parkinson Prognosis With Protection

One of the known markers for PD is low glutathione in the substantia nigra – which was also the case for these animals that were given rotenone and iron.

Glutathione is the body’s “protective molecule” and is typically depleted in the brains of Parkinsons patients.

Increasing glutathione in the substantia nigra, they found, gave the test animals “dopaminergic neuroprotection” and decreased the damage caused by these toxins.

This molecule can also protect against the eventual toxic effect of the Parkinsons medications which cause dyskinesia or “shaking:”

See: Dyskinesia caused by Parkinsons Medications, Carbidopa, Levodopa

Is Parkinsons Disease Hereditary

The search for environmental causes of Parkinson

Hereditary diseases are passed from parents to their children, but cases of familial Parkinsons disease are very rare . The vast majority of Parkinsons cases are not transmissible.

Having Parkinsons disease does not affect your childrens risk of developing the disease. Similarly, your risk is not increased if your brother or sister has the disease. However, your risk may be increased if more than one person in your family has the disease.

Exposure to certain environmental factors or toxins may contribute to the development of Parkinsons disease.

The main environmental factors involved in Parkinsons disease are:

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The Five Environmental Causes Of Parkinsons Disease

Parkinsons disease is a brain disorder that develops and becomes worse over time. The typical symptoms of the disease include tremor, stiffness, slowness of movement, and balance problems. These symptoms develop when the brain lost its ability to produce a sufficient amount of dopamine, a neurotransmitter responsible for controlled body movement.

Researchers have identified a variety of environmental factors that are linked to Parkinsons disease. Some of these factors may directly cause the disease symptoms, others may increase the risk of developing it.

Here are the 5 main environmental factors that are linked to Parkinsons disease development.

Need To Know: Dr Ray Dorsey

Dr Ray Dorsey is David M Levy Professor of Neurology and Director at the Center for Health + Technology at the University of Rochester Medical Center, US, which has conducted more than 100 clinical trials including trials that led to the approval of four Parkinsons medications. He recently co-wrote the book,Ending Parkinsons Disease: A Prescription for Action.

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Reasons Why Parkinsons Disease Occurs

The scientific reason given for Parkinsons disease is that the patient has lost nerve cells in the part of the brain called the substantia nigra. A very important chemical called dopamine is produced by the substantia nigra. The loss of the ability to produce dopamine contributes to the early stages of Parkinsons disease.

What Protects Best Against Parkinsons

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While Parkinson causes are multiple, researchers have also found what can protect best.

Even for different Parkinson stages and early symptoms of Parkinson, here is what scientists found to be protective against risk factors:

  • A diet high in flavonoids and antioxidants
  • drinking coffee
  • being active and getting exercise 4

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What Raises Someone’s Risk For Parkinson’s

It’s a complex picture, but you may be more likely to get Parkinson’s based on:

Age. Since it mostly affects people 60 and older, your risk goes up as the years go by.

Family history. If your parent, brother, or sister has it, you’re a little more likely to get it.

Job. Some types of work, like farming or factory jobs, can cause you to have contact with chemicals linked to Parkinson’s.

Race. It shows up more often in white people than other groups.

Serious head injury. If you hit your head hard enough to lose consciousness or forget things as a result of it, you may be more likely to get Parkinson’s later in life.

Gender. Men get it more than women. Doctors aren’t sure why.

Where you live. People in rural areas seem to get it more often, which may be tied to chemicals used in farming.

Want To Learn More About The Latest Research In Parkinsons Disease Ask Your Questions In Our Research Forum

Environmental factors may trigger Parkinsons or modify its progression during the prodromal stage, in which early symptoms or signs are present, but clinical diagnosis is not yet possible. Among the reported factors, smoking, coffee, exercise, plasma urate, and use of ibuprofen have been linked to a lower risk of Parkinsons, while pesticide exposure and traumatic brain injury have been associated with a greater risk.

Apart from two pesticides known as rotenone and paraquat, researchers have had difficulties in providing evidence that other risk factors can cause the disease. Reverse causation meaning that Parkinsons changes lifestyle and behavior before a clinical diagnosis rather than the other way around has been proposed as an explanation for the link between these environmental triggers and Parkinsons in its early stages.

This prodromal stage is of major interest for prevention efforts, the researchers said in the release, adding that the discovery of Lewy bodies protein aggregates mainly composed of alpha-synuclein that are characteristic of Parkinsons in the olfactory pathway and the digestive tract made targeting factors that enter the body via the nose or gut even more important.

We are at an exciting moment to unveil environmental contributions to development and progression by taking a life-course approach, and utilizing novel tools to assess environmental exposures, the researchers said.

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Environmental And Other Factors

Scientists have been meticulously scanning through non-genetic factors that influence PD risk. Putting yourself in their shoes, you may understand how challenging this must be with the numerous possibilities. But what can come out of this endeavor has magnificent potential in the intervention and prevention of PD.

Most cases of PD are sporadic and not genetic. Often, lifestyle and environmental factors stave off the onset of PD in individuals who are genetically predisposed to it.

The following are the most prominent factors:

1. Age

PD usually starts showing up around 60, and most patients are above 85.

Parkinsons disease is the second most common age-related neurodegenerative disorder after Alzheimers.9 Over 1% of the population over the age of 60 and 5% over 85 suffer from PD. Only a small 5% of PD cases advance before 60 years of age and are linked to gene mutations.

With advancing age, the neurons in the substantia nigra are faced with an entourage of stressors such as free radicals from dopamine metabolism and a dearth of cellular energy. Together, these make the SN neurons more vulnerable to degeneration than other parts of the brain.

2. Gender

Parkinsons is 1.5 to 2 times more common in men than women.

3. Toxin Exposure

Most people who are exposed to pesticides do not develop PD. Those who do usually also have a gene mutation that affects dopamine transport.

4. Head Trauma

The Link Between Alcohol And Parkinsons Is Not Yet Established

Advancing Age And Parkinsons Disease


Age is perhaps the biggest risk factor for the onset of Parkinsons disease. The average age at which people will develop this movement disorder is 60. This is not usually something that affects younger people. The brain ages as people get older.

Even without external factors, cells in the substantia nigra can die on their own as an individual ages, causing symptoms to develop as the person gets older.

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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.

Parkinson Causes: What Adds Up To Trigger The Disease

Researchers say that Parkinson causes are “multifactorial”. 1

Risk factors that add up as Parkinson Disease causes, are exposure to:

  • pesticides
  • environmental toxins and metals e.g. manganese, iron
  • drugs
  • genomic defects
  • injury in a specific location of the brain , resulting in neurologicdysfunction

Some or all factors combine in the brain and nervous system and cause:

  • neuro-toxicity
  • oxidative stress

A combination of factors can converge over a lifetime as Parkinson causes:

  • For instance, when researchers fed extra metal – iron – and the pesticide rotenone to experimental animals, this led to Parkinsons Disease in the substantia nigra part of the brain.
  • However, when they gave only one of these, or each separately — just iron or rotenone alone — this did not happen.2

Is Parkinson’s a Syndrome rather than a specific Disease?

There is evidence that instead of long term chronic exposure, there was likely a more specific “environmental” or toxic event or exposure.

This would have killed some nigraldopaminergic cells, and damaging others. 3

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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.

Environmental Causes Of Parkinsons Disease

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

Parkinsons Disease causes are classified as environmental causes due to the fact that they occur through exposure to certain drugs which has been proven in scientific studies.

The most common sign of parkinsonism is a resting tremor, which causes shaking when the individual assumes or is forced into certain positions.

Other less frequent symptoms are impaired movement and balance problems due to changes in muscle stiffness, slow movements, rigidity, sleep disturbances, mood changes, and difficulty speaking or swallowing.

Symptoms worsen with time as the disease progresses to its final stages where it causes an inability to walk, talk, swallow properly, stay awake for a long period of time.

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The Search For Environmental Causes Of Parkinson’s Disease Moves Forward

IOS Press
Scientists evaluate promising research hypotheses for understanding environmental triggers in Parkinson’s disease and propose future directions for research.

Environmental factors are widely believed to play a key role in the development of Parkinson’s disease , but little is known about specific environmental triggers. Writing in the Journal of Parkinson’s Disease, scientists review novel research hypotheses and approaches that may help better define the role of environment in the development of PD, especially before a diagnosis can be made based on the characteristic motor dysfunction for which PD is known.

Late-onset sporadic PD takes decades to develop, and by the time of diagnosis, some of the neurodegenerative changes are too advanced to slow down, stop, or reverse. On the other hand, environmental factors that cause or trigger its development and modify its progression may come into play during the “prodromal phase,” decades before specific signs and symptoms develop. “This prodromal stage is of major interest for prevention efforts,” explained the authors. “Targeting factors that enter the body via the nose or gut has become even more important since the discovery that the alpha-synuclein protein-related Lewy pathology, which is characteristic of PD, was identified in the nervous systems of the olfactory pathway and the digestive tract.”

Braak Hypothesis

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Now Is A Major Opportunity To Move Forward

Although still somewhat controversial, the Braak hypothesis presents a unique hypothetical framework of PD development that may allow us to better conceptualize steps of PD prodromal development and environmental contributions. According to this hypothesis, PD Lewy pathology develops in six sequential stages, first in the olfactory bulb or enteric nerves , years if not decades, before spreading to the substantia nigra where dopaminergic neuron death occurs . In support of this hypothesis, recent clinical and epidemiological studies have clearly documented a wide range of nonmotor symptoms in PD patients, and some symptoms such as olfactory impairment , REM sleep behavior disorder , and constipation may have developed years, if not decades, prior to PD clinical diagnosis. While there are still substantial challenges to adequately define prodromal PD, by using these symptoms as noninvasive intermediate phenotypes, we may be able to bring new insights into this black-box of PD prodromal development by identifying factors that initiate PD pathogenesis, lead to these intermediate phenotypes, or modify progression to clinical PD . This framework may fundamentally improve understanding of PD prodromal development and contributions from environmental factors.

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Environmental Factors In Parkinsons Disease

Here are environmental factors that may play a role in the development of Parkinsons disease:

Although environmental exposure to these and other toxins is of continued research interest, its hard to determine if any one substance is a culprit. Most often, individual cases of Parkinsons disease result from a complex interplay between genetics and environmental and other factors.

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Researchers report they have discovered how two problem proteins known to cause Parkinsons disease are chemically linked, suggesting that someday, both could be neutralized by a single drug designed to target the link.

Study Links Genetic Environmental Causes Of Parkinson’s

Schematic presentation of neuronal death in Parkinson

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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Ask Us For A Recommendation

Best neuro-protective foods and supplements.

You may ask us about:

  • Supplements scientifically shown to replenish glutathione levels to protect against cell death and toxins
  • Glutathione-building supplement for detoxifying metals and pesticides

We hope that you have been inspired for better Parkinson Disease treatments with natural help.

  • Knowing that yes, that environmental toxins lead to Parkinson is hopefully less scary, because there are prptective foods and supplements.
  • For your best shot at a Parkinson cure, you will want to add the best foods and supplements shown to be neuro-protective.

Metals such as iron are usually high in the brains of Parkinsons patients. Iron can be reduced in the body by:

  • not taking iron supplements
  • eating less red meat
  • donating blood
  • drinking green tea and adding curcumin to your food. These contain natural iron-chelating, substances – molecules that bind to and remove iron.

Knowing the causes Parkinson Disease will hopefully help live a fuller and longer life!


1. Int J Mol Sci. Parkinsons Disease: From Pathogenesis to Pharmacogenomics 2017 Mar 18: 551. Published online 2017

2. Front Neurosci. Neurochemical and Behavior Deficits in Rats with Iron and Rotenone Co-treatmen. 2017 Nov 23 11:657. doi: 10.3389/fnins.2017.00657. eCollection 2017.

3. PARKINSONS DISEASE: A SYNDROME NOT ADISEASE Issue: BCMJ, vol. 43 , No. 3, April 2001 , Pages 129-132Clinical Articles By: Donald B. Calne, OC, DM

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