Parkinson’s Disease Linked to Pesticides

Summary
Parkinson’s disease is a degenerative brain disorder characterized by the loss of specific neurons in the brain. Pesticides damage cells and have been found to cause degenerative diseases. In previous animal laboratory studies, pesticides like rotenone have been shown to produce a loss of neurons and development of Parkinson’s disease. However, the link between pesticides and Parkinson’s disease was not strongly established. This present population-based study found a strong association between human occupational exposure to pesticides and the development of Parkinson’s disease.

Introduction
Two possible causes of Parkinson’s disease are injury to your cells by oxidative stress or the mechanism that creates energy for your cells, called the mitochondiral, can dysfunction. Two insecticides — paraquat, which causes oxidative stress, and rotenone, which causes mitochondrial dysfunction — have previously been linked to Parkinson’s disease. But past reports were inconsistent and evidence concerning rotenone was sparse. The Farming and Movement Evaluation study (FAME) is a sub-study from the larger Agricultural Health Study (AHS). It included 84,740 people that used pesticide in addition to their spouses from Iowa and North Carolina. Current research followed this population looking for a possible link between pesticide use and development of Parkinson’s disease.

Methodology
* From the FAME study population, pesticide users, mostly farmers and their spouses who potentially had Parkinson’s disease, were identified by self-report or state mortality files. Controls were selected by a random sampling from the same subgroup.
* Two neurologists examined potential Parkinson’s patients independently and diagnosis was confirmed when the two neurologists concurred. The controls were screened by people trained by neurologists to identify features of Parkinson’s. The final report included 110 Parkinson’s cases and 358 controls.
* Information regarding lifetime exposure to pesticides, types of pesticide used, tobacco use and family history of Parkinson’s disease was gathered from all participants.

Results
* Of women, 44 percent had used pesticides; and 98 percent of the men had.
* Both rotenone and paraquat were strongly associated with Parkinson’s disease. Parkinson’s disease was found 2.5 times more often in people who were exposed to rotenone, compared to non-users. The risks were the same even if exposure was 15 years before the diagnosis.
* Race/ethnicity, cigarette use, state or duration of disease were not appreciably different between subgroups of rotenone and paraquat users.
* Parkinson’s disease was diagnosed at a younger age among those who used insecticide causing oxidative stressors, like paraquat.

Next steps/Shortcomings
The participants had a history of exposure to many pesticides; as a result, other pesticides could have contributed to the development of Parkinson’s as well. The study did not determine laboratory measures of pesticides that were used or their metabolic end products. The participants were included if the patient self-reported having symptoms of Parkinson’s disease, or if they were already diagnosed, as well as if they lived close by. Only those pesticides whose mode of action was known were included in this study, but the exact toxic effects of many pesticides are unknown and could contribute to Parkinson’s disease. This study may not be fully representative of the entire population and additional research is required.

Conclusion
This study found a significant association between exposure to certain pesticides and the development of Parkinson’s disease. Rotenone is derived from plants and is considered relatively safe. Paraquat is one of the most widely used herbicides in the world. Parkinson’s disease was diagnosed earlier in paraquat users as this pesticide produces oxidative damage to cells. Oxidative injury to genes is implicated in genetic forms of Parkinson’s disease. This study was based only on occupational exposure to pesticides. Many more people might be unaware of the presence of pesticides in their environment. As a result, findings of this study have great public health significance. The findings of this study indicate the need for more research in gene-exposure interaction caused by pesticides.

For More Information:
Rotenone, Paraquat and Parkinson’s Disease
Environmental Health Perspectives, Jan 2011
By Caroline M. Tanner, MD, PhD; Freya Kamel; The Parkinson’s Institute, Sunnyvale, California, and the National Institute of Health, U.S. Department of Health and Human Services, North Carolina

*FYI Living Lab Reports Are Summaries of the Original Research.