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Parkinson's Disease

Parkinson's disease (PD) is a chronic neurodegenerative disease caused by the death of clusters of cells in the midbrain that leads to the reduction of dopamine – a neurotransmitter responsible for coordinating muscle movement. The lack of dopamine causes the varied symptoms of PD which include: tremor, slow movement, muscle rigidity, poor balance and the loss of smell, taste, and reduced range of facial expressions. There are approximately 6.3 million people around the world suffering from PD (1).

The causes of PD are still unknown. Scientists estimate that genetics are responsible for fewer than 1% percent of all cases. In people who show symptoms before the age of 50, research shows that genetics play a role in 5-10% of cases (2). Scientists now believe that it is the combination of genetic predisposition and environmental factors that causes PD (3). Scientists are paying special attention to chemical (especially pesticides) and heavy metals exposures as possible causes for the onset of PD.

Epidemiologists at UCLA have found that 75% of people living within 500 meters from agriculture plants using the herbicide paraquat and the fungicide maneb had an increased risk of developing PD (4). Scientists have also found an increased number of PD patients in a population that worked for over 20 years with heavy metals like iron, lead, copper, manganese, and zinc (2).

A recent research found that even relatively limited exposure to some common chemical solvents at work or through hobbies may increase the risk of having Parkinson's disease, regardless of the number of exposures and their duration. The researchers recruited 99 male twin pairs where only one brother was diagnosed with PD. Through questionnaires, researchers found that "Ever" exposure to TCE (a metal degreaser, in use in dry cleaning and as an additive in glues, carpet cleaners and other products) was associated with a 6-fold increase in the odds of having PD, while "ever" exposure to PERC (a dry cleaning agent and degreaser) also increased the disease risk. Combined exposures to TCE and PERC increased disease risk by nine fold. Duration of exposures did not alter PD risk (5).

Parkinson's disease in Israel

The National Insurance Institute of Israel recognizes PD as an occupational disease, which might be caused as a result of exposure to chemicals. The exact number of people suffering from PD in Israel is unknown, since an epidemiological survey was never conducted. The following studies provide some understanding of the PD prevalence around Israel.

Research focusing on PD drug purchase in Israel has estimated about 20,000 PD patients, an increase over the previous decade (6).
Research conducted among the Arab-Israeli population in the Wadi Ara region has identified Baka-El-Garbia as an area where PD prevalence is particularly high. While the prevalence of PD among Israeli-Arabs tends to be lower in comparison to the general population, scientists have found that the prevalence of PD in Baka-El-Garbia was twice as high as that in Umm-El-Fahm. Most of the residents of Baka-El-Garbia work in agriculture and the area is surrounded by fields that are regularly sprayed with herbicides and pesticides by small airplanes. Scientists believe these parameters account for the difference in prevalence (7).
A high prevalence of PD was found also among residents of three kibbutzim in southern Israel. In a study conducted in 1989, it was found that among people older than 40, PD was about five times greater in each of these kibbutzim than in the remainder of the Negev. Since no new or further research has been conducted, there are no new data regarding this matter (8).

Recently, the Ministry of Health approved a plan for creating a national PD registry based on drug purchase data from HMO databases. Haifa and Tel Aviv Universities and the Israeli Center for Disease Control are collaborating in the development of the registry (9). The registry will enable the Ministry of Health to characterize PD patients in terms of age, residence, socio-economic status, environmental and occupational exposures. With these tools, the registry will allow researchers to explore whether the number of patients is increasing, decreasing or remaining stable and whether some parts of the country show higher incidence than others. The data collected from the registry will allow scientists to learn more about PD and work to develop better treatment. To date, only cancer and birth defects are being registered on a national scale. These registries contribute to a better understanding of Israeli population's health condition as well as recommendations for preventing and treating these severe conditions.

References

1) de Lau, LM and Breteler MM,. "Epidemiology of Parkinson's disease," Lancet Neurology, 5(6) (2006). http://www.thelancet.com/journals/laneur/article/PIIS1474-4422%2806%2970471-9/abstract

2) National Institute of Environmental Health Sciences. "The Role of the Environment in Parkinson's Disease," National Institutes of Health. www.niehs.nih.gov/health/topics/conditions/parkinson/index.cfm
3) "Environmental Threats to Healthy Aging," Greater Boston Physicians for Social Responsibility and Science and Environmental Health Network. http://www.agehealthy.org/
4) National Institute of Environmental Health Sciences. “Pesticide Exposure Raises Risk of Parkinson’s Disease.” National Institutes of Health. www.niehs.nih.gov/research/supported/sep/2009/pesticide.cfm

5) http://www.environmentalhealthnews.org/ehs/newscience/2011/12/2012-0220-solvent-increases-parkinsons-risk/
6) Chillag-Talmor O et al. "Using drug purchase data to estimate the occurrence of Parkinson's disease in Israel, 1998-2008." Annual neurological conference. 2010. medicine.tau.ac.il/fair-abstracts/uploads/Z7.doc
7) Masalha R et al. "The prevalence of Parkinson's disease in an Arab population, Wadi Ara, Israel." Israel Medical Association Journal. 2010 Jan;12(1):32-5. www.ncbi.nlm.nih.gov/pubmed/20450126
8) Herishanu YO. Clustering of Parkinson's disease in southern Israel. Can J Neurol Sci. 1989 Nov;16(4):402-5. http://www.ncbi.nlm.nih.gov.ezproxy.bu.edu/pubmed/2804801
9) Peretz C. et al., Parkinson’s Disease in Israel, EHF grant no. SGA0209

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