Parkinson’s disease (PD) is a degenerative disorder of the central nervous system that often impairs the sufferer’s motor skills and speech. It is the second most common neurodegenerative disease after Alzheimer’s disease. There is evidence that both genetic and environmental factors are important determinants, and a family history of the disease has been shown to be a risk. Different studies have investigated the relationship between PD and pesticide use. Some of them, but not all, have found an association but to date no specific agent has been implicated consistently and the degree of pesticide exposure that might result in PD remains unknown.

As a part of the EU-funded research project Geoparkinson, European researchers, have recently investigated the relation between exposure to solvents, pesticides, iron, copper and manganese and the risk of PD. To this end, the authors undertook a case-control study of 959 prevalent cases of Parkinsonism (767 with Parkinson’s disease) and 1989 controls in Scotland, Italy, Sweden, Romania, and Malta. Subjects completed an interviewer-administered questionnaire regarding lifetime occupational and hobby exposure to these substances. Lifetime and average annual exposures were estimated and statistical analysis was applied. The Geoparkinson project is one of the largest case-control studies to date of genetic, environmental, and occupational risk factors for Parkinson’s disease or other degenerative Parkinsonian syndromes.

The researchers found that Parkinson’s disease is associated with pesticide use. Previous studies have established an association but few had been able to establish an exposure-response relationship, perhaps due to small sample size or poor exposure assessment.

The results suggest that relatively low intensity exposure to pesticides may increase risks. On the other hand, they suggest that in general, risk from solvents and metals are less important in this respect.

Overall, the exposure-response relationship suggests that pesticide exposure may be a causative and potentially modifiable risk factor. This has implications for occupational and, perhaps, recreational users of these agents. Further research is needed to establish which pesticides are associated with this effect.

Source: Finlay D. Dick et al. (2007), « Environmental risk factors for Parkinson’s disease and parkinsonism: the Geoparkinson study », Occup Environ Med, doi:10.1136/oem.2006.027003.