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What Causes Parkinson's?

We do not yet know what causes Parkinson’s disease (PD) to develop in most people.

Experts have identified aging as an important factor that contributes to Parkinson’s in some individuals. For example, people over age 60 have a two-to-four percent risk of developing Parkinson's disease, compared with the one-to-two percent risk in the general population.

While there are certain families who share a gene that leads to Parkinson’s, this is a small percentage of the population with PD. Most Parkinson’s disease cases are sporadic — meaning that genetics and family history have not played a clear role in the onset and development of the disease.

Scientists suspect that for most people, the cause is probably a combination of genetic and environmental factors. They believe these factors may vary from person to person.

Read more below about each of these:

Genetic Factors

Of the one million individuals in the US who live with Parkinson’s, scientists believe that only about five percent have an inherited form of the disease.

What is your risk if a loved one has PD, or you have the disease and are concerned about your children and grandchildren? Probably only slightly higher than the general population. Large epidemiological studies (studies that deal with incidence, distribution and control of disease in a population), demonstrate that people with an affected first-degree relative, such as a parent or sibling, have a two-to-three fold increased risk of developing Parkinson's, as compared to the general population.

Scientists have identified 13 genes that are associated with Parkinson’s and can cause the disease in a small number of families. In these families, genes involve proteins that play a role in dopamine cell functions.

Although genetics play a role in only a small number of Parkinson’s cases, they are currently the subject of intense research. This is because genetic forms can be studied in great detail in the laboratory, and because understanding the rare genetic forms of Parkinson's disease may help to understand more common forms of the disease.

The genes identified to date include: PARK1, DJ-1 (PARK7), Pink1 (Park6), dardarin (DRDN), Tau, lrrk2, parkin, uchl-1, park3, park9, park10, park11.

Learn more by reading, Nature Versus Nurture: What Causes PD?

Environmental Factors

Some scientists have suggested that Parkinson's disease may result from exposure to an environmental toxin or injury. However, there is no conclusive evidence that any environmental factor, alone, can be considered a cause of the disease

To date, epidemiological research has identified rural living, well water, herbicide use and exposure to pesticides, as factors that may be linked to Parkinson’s. Additionally, a synthetic narcotic agent called MPTP (1-methyl 4-phenyl 1, 2, 3, 6-tetrahydropyridine) can cause immediate and permanent Parkinsonism if injected.

These environmental factors are not useful in diagnosing the cause of Parkinson's disease in individual people. However, they have been helpful in studying laboratory models of Parkinson's disease.

For instance, the discovery of MPTP has allowed researchers to study animals with Parkinson’s symptoms, both to learn about how cells die and how Parkinson’s develops and to test treatments. Furthermore, MPTP gave scientist a clue to finding environmental links to Parkinson’s. The chemical structure of MPTP is very much like the widely used herbicide paraquat and damages cells in a way similar to the pesticide rotenone, as well as some other substances. This has led researchers to investigate whether exposures to those substances increases the risk of Parkinson’s.

Scientists are continuing to pursue these clues to establish more concrete linkages.


In Depth Look: Genetics and PD

Next: Medications & Treatments

More Questions?

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