Abstract
Background: Previous studies repeatedly suggested that Parkinson’s disease (PD) is associated with occupational pesticide exposure, but in many studies exposures were self-reported and none adjusted for concomitant ambient pesticide exposures. Objective: To investigate whether occupational exposure to pesticides increases the risk of PD in California’s heavily agricultural region. Methods: We enrolled 357 incident PD cases and 750 population controls in a case-control study in California’s Central Valley between 2001 to 2011. A comprehensive Job Exposure Matrix (JEM) was developed to assess participant’s life-time cumulative occupational pesticide exposure based on work history and detailed job tasks information. Results: PD risk was estimated to be more than 2-fold higher (OR=2.19 95%CI 1.26, 3.82) in men who were classified as highly occupational exposed with our data suggesting an exposure-response (trend p=0.007). Farming tasks with more direct and intense pesticide exposures such as applying, spraying and mixing of pesticides resulted in greater risks than indirect exposures from general tasks such as planting, harvesting, packing, sorting, etc. Results did not change when we adjusted for residential and occupational ambient pesticide exposures estimated based on a Geographic Information System (GIS) model. Conclusion: We provide further evidence that occupational pesticide exposure increases the risk of PD in men and ambient exposures did not confound these associations.
Highlights
Parkinson's disease (PD) is the second most common neurodegenerative disorder leading to motor, cognitive and mood dysfunction with a major impact on quality of life
Parkinson’s disease (PD) has been linked to farm work and pesticide exposures in general with some studies reporting on specific pesticide exposures including our own previous reports focused on ambient pesticides in proximity to agricultural applications
Few studies utilized methods less influenced by subject recall such as exposure matrices or expert evaluations based on job history to assess occupational pesticide exposures but most of these studies were either very small (
Summary
Parkinson's disease (PD) is the second most common neurodegenerative disorder leading to motor, cognitive and mood dysfunction with a major impact on quality of life. The vast majority of previous epidemiological studies relied on retrospective selfreporting of exposures raising questions about validity due to the possibility of differential recall bias since cases may be more inclined than control subjects to report exposures to suspected toxins as suggested previously. This German study found PD risk to be increased with selfreported pesticide use but not when a job exposure matrix was employed to assess pesticide exposures. Previous studies repeatedly suggested that Parkinson’s disease (PD) is associated with occupational pesticide exposure, but in many studies exposures were self-reported and none adjusted for concomitant ambient pesticide exposures
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