Twin study finds occupational chemical exposure may be linked to Parkinson's risk

November 14, 2011 in Parkinson's & Movement disorders

A new research report contributes to the increasing evidence that repeated occupational exposure to certain chemical solvents raises the risk for Parkinson's disease. Researchers analyzed the occupational histories of twins in which one of the pair developed the neurodegenerative disorder, and assessed that twin's likelihood of exposure to six chemicals previously linked to Parkinson's. Of the six chemicals investigated, researchers concluded that two common chemical solvents, trichloroethylene (TCE) and perchloroethylene (PERC), are significantly linked to development of this disease. This study, supported in part by the National Institute of Neurological Disorders and Stroke (NINDS), a part of the National Institutes of Health, appears in the Nov. 14, 2011 issue of Annals of Neurology.

Parkinson's disease is a movement disorder caused by the loss of that produce a molecule called dopamine. The primary symptoms of Parkinson's are tremor, stiffness, slowed movement and impaired balance, and as these symptoms progress, patients may also develop difficulty walking, speaking or completing other activities of daily living. Genes play a role in Parkinson's disease, but fewer than 10 percent of cases are due to a single , and not all people with these mutations develop Parkinson's, suggesting that environmental factors also contribute to the likelihood of developing the disease.

The researchers, led by Samuel Goldman, M.D., M.P.H. and Caroline Tanner, M.D., Ph.D. at the Parkinson's Institute in Sunnyvale, Calif., collected the histories of 99 pairs of in which one of the pair developed Parkinson's and the other twin did not. Since twins are so genetically similar, twin studies are especially useful in identifying in disease. The twins were identified through the National Academy of Sciences/National Research Council World War II Veteran Twins Registry. Of the 99 pairs, half were genetically , and half were fraternal twins.

The study team assessed the twins' lifetime work and hobby activities, specifically inquiring about occupational tasks such as electrical work, industrial machinery repair, and dry cleaning, which would potentially expose people to chemicals previously linked to Parkinson's. The researchers also collected information on head injuries, which are suspected to increase Parkinson's risk, and smoking history, which is reported to decrease Parkinson's risk. Expert evaluators, unaware of which study subjects had Parkinson's, reviewed this information and calculated lifelong exposure to six chemicals: TCE, PERC, carbon tetrachloride, n-hexane, xylene and toluene. Of these, TCE and PERC posed a notable risk for developing Parkinson's.

"The potential importance is great, since both solvents persist in the environment and are commonly used," said Dr. Goldman, "Parkinson's was sixfold more common in twins exposed to TCE, and ninefold more common in twins exposed to TCE or PERC." There was also a trend toward a tenfold increase in Parkinson's disease in twins exposed to PERC alone.

In this study researchers looked only at occupational chemical exposure, and the association with job categories tended toward significance only for the industrial machinery repairer and industrial worker categories. However, the chemicals evaluated here are found outside industrial settings as well. PERC is the leading chemical used in garment dry cleaning. TCE is the most frequently reported organic groundwater contaminant, was once used as general anesthetic and coffee decaffeinating agent, and is still used widely as a metal degreasing agent.

TCE has also been linked to Parkinson's by other research groups. Researchers at the University of Kentucky, Lexington, and the Kangwon National University in South Korea have reported an association between TCE and Parkinson's in highly-exposed industrial workers, and have also demonstrated that TCE causes neurodegeneration in animal models.

The analysis described in this report expands on preliminary findings presented at the 2010 American Academy of Neurology meeting. The new paper quantifies the individuals' exposures to the chemicals in terms of successive years and cumulative exposure over their lifetime.

Dr. Tanner notes that while the association between chemical exposure and Parkinson's is strong, one limitation of the research is the small number of individuals studied. "It will be important to replicate these results in additional populations with well-characterized exposure histories," she commented.

Wendy Galpern, M.D., Ph.D., program director at NINDS, agreed that replication of these results is necessary. "This epidemiologic study is a noteworthy addition to our growing understanding of the association between environmental exposures and Parkinson's disease," Dr. Galpern said. "The identification of specific chemicals linked to this may have implications for disease prevention and an improved understanding of how Parkinson's develops."

More information: "Solvent Exposures and Parkinson's Disease Risk in Twins"; Samuel M Goldman, Patricia J Quinlan, G Webster Ross, Connie Marras, Cheryl Meng, Grace S Bhudhikanok, Kathleen Comyns, Monica Korell, Anabel R Chade, Meike Kasten, Benjamin Priestley, Kelvin L Chou, Hubert H Fernandez, Franca Cambi, J William Langston and Caroline M Tanner. Annals of Neurology; Published Online: November 14, 2011 (DOI:10.1002/ana.22629).

Journal reference: Annals of Neurology search and more info website

Provided by National Institutes of Health

5 /5 (2 votes)  

Rank 5 /5 (2 votes)
Relevant PhysicsForums posts

More news stories

Faulty energy production in brain cells leads to disorders ranging from Parkinson's to intellectual disability

Neuroscientist Patrik Verstreken of VIB (Flanders Institute for Biotechnology) and KU Leuven has shown for the first time that dysfunctional mitochondria in brain cells can lead to learning disabilities. The link between ...

Parkinson's & Movement disorders created May 17, 2013 | popularity 4 / 5 (2) | comments 0

Unleashing the watchdog protein

McGill University researchers have unlocked a new door to developing drugs to slow the progression of Parkinson's disease. Collaborating teams led by Dr. Edward A. Fon at the Montreal Neurological Institute and Hospital -The ...

Parkinson's & Movement disorders created May 09, 2013 | popularity 5 / 5 (1) | comments 0 | with audio podcast

Could eating peppers prevent Parkinson's? Dietary nicotine may hold protective key

New research reveals that Solanaceae—a flowering plant family with some species producing foods that are edible sources of nicotine—may provide a protective effect against Parkinson's disease. The study appearing today ...

Parkinson's & Movement disorders created May 09, 2013 | popularity not rated yet | comments 0

Study reveals probable role of Parkinson's protein in healthy brain

(Medical Xpress)—Researchers at the Stanford University School of Medicine have exposed the possible function, in the healthy brain, of a mysterious molecule that has been strongly implicated in Parkinson's ...

Parkinson's & Movement disorders created May 01, 2013 | popularity 5 / 5 (3) | comments 0 | with audio podcast

Study shows how Parkinson's disease protein acts like a virus

A protein known to be a key player in the development of Parkinson's disease is able to enter and harm cells in the same way that viruses do, according to a Loyola University Chicago Stritch School of Medicine study.

Parkinson's & Movement disorders created Apr 25, 2013 | popularity 5 / 5 (5) | comments 0 | with audio podcast


Research examines new methods for managing digestive health

Research presented at Digestive Disease Week (DDW) explores new methods for managing digestive health through diet and lifestyle.

New research identifies practice changes to improve value and quality of GI procedures

There are significant cost and risk factors associated with two procedures commonly used to diagnose or treat gastrointestinal problems, according to research presented at Digestive Disease Week (DDW).

New smartphone application improves colonoscopy preparation

The use of a smartphone application significantly improves patients' preparation for a colonoscopy, according to new research presented today at Digestive Disease Week (DDW). The preparation process, which begins days in ...

Ketamine shows significant therapeutic benefit in people with treatment-resistant depression

Patients with treatment-resistant major depression saw dramatic improvement in their illness after treatment with ketamine, an anesthetic, according to the largest ketamine clinical trial to-date led by researchers from the ...

Consuming coffee linked to lower risk of detrimental liver disease, study finds

Regular consumption of coffee is associated with a reduced risk of primary sclerosing cholangitis (PSC), an autoimmune liver disease, Mayo Clinic research shows. The findings were being presented at the Digestive Disease ...

New research identifies risks, interventions for children's GI health

An increasing number of U.S. children are experiencing gastrointestinal issues that require interventions to resolve, according to research presented at Digestive Disease Week (DDW).