Environmental risk factors and Parkinson's disease

Abstract

To explore environmental risk factors for Parkinson's disease (PD) in Taiwan, we investigated 120 patients with PD and 240 hospital control subjects matched with patients on age (+/-2 years) and sex. Based on a structured open-ended questionnaire, we carried out standardized interviews to obtain history of exposure to environmental factors, including place of residence, source of drinking water, and environmental and occupational exposures to various agricultural chemicals. In the univariate analysis, the history of living in a rural environment, farming, use of herbicides/pesticides, and use of paraquat were associated with an increased PD risk in a dose-response relationship. After adjustment for multiple risk factors through conditional logistic regression, the biological gradient between PD and previous uses of herbicides/pesticides and paraquat remained significant. The PD risk was greater among subjects who had used paraquat and other herbicides/pesticides than those who had used herbicides/pesticides other than paraquat. There were no significant differences in occupational exposures to chemicals, heavy metals, and minerals between PD patients and matched control subjects. The duration of drinking well water and alcohol consumption was not significantly associated with PD. There was an inverse relationship between cigarette smoking and PD. Environmental factors, especially exposures to paraquat and herbicides/pesticides, may play important roles in the development of PD in Taiwan.

Epidemiology and etiology of Parkinson’s disease: a review of the evidence

“…In most studies of pesticides in relation to PD exposure was assessed retrospectively as a broad category, rather than examining specific substances. Of 38 case-control studies, 19 reported increased risk of PD [147,154,156,[289][290][291][292][293][294][295][296][297][298][299][300][301][302][303][304] with ORs ranging between 1.3 and 3.7 for most studies. One study reported an OR of 7.0 (p value <0.05) [289] and another an OR of 10.9 (95% CI 2.5-48.0) [301].…”

“…A hospital-based study found an increased risk of PD with overall pesticide or herbicide use (OR 2.89, 95% CI 2.28-3.66); the risk increased with longer duration of exposure (OR 6.72, 95% CI 2.62-12.21 for more than 20 years of exposure versus none) [293]. One population-based study reported increased risk of PD following occupational exposure to pesticides (OR 2.25, 95% CI 1.27-3.99) without a dose-response relationship [290].…”

“…On the other hand, smoking may be associated with higher exposure to pesticides (for example, one study showed that smoking was associated with higher levels of polychlorinated biphenyls and organochlorine pesticides in breast milk samples [318]), which would confound an association between pesticides and PD towards the null. Adjustment for smoking, however, gave lower risk estimates for pesticides than unadjusted analyses in several of the studies [144,147,293,319]. A substantial proportion of the studies that observed no association between pesticides and PD did not adjust for smoking in the analyses [131, 136, 141, 142, 145, 305-309, 311, 314, 315].…”

“…Some case-control studies reported results for specific categories of pesticides, such as herbicides, insecticides, or fungicides, rather than pesticides overall. Of 18 studies that analyzed exposure to herbicides, 10 found increased risk of PD, either for herbicides as a group of substances, or for specific herbicides, such as paraquat, nitrile herbicides or 2,4-Dichlorophenoxyacetic acid [153,154,290,293,302,304,[321][322][323][324], with ORs ranging between 1.6 and 5.8. The other 8 studies reported no association between herbicides and PD [131,143,292,299,301,315,316,325].…”

“…The hospital-based study that reported a dose-response relationship for overall pesticide or herbicide use [293] also reported a relationship for paraquat. Four other studies that assessed paraquat specifically, however, found no association [292,301,304,316,317], although one [304] reported increased risk of PD following exposure to 2,4-Dichlorophenoxyacetic acid (OR 2.59, 95% CI 1.03-6.48).…”