Pesticide exposure and risk of Parkinson's disease: A family-based case-control study

Abstract

BackgroundPesticides and correlated lifestyle factors (e.g., exposure to well-water and farming) are repeatedly reported risk factors for Parkinson's disease (PD), but few family-based studies have examined these relationships.MethodsUsing 319 cases and 296 relative and other controls, associations of direct pesticide application, well-water consumption, and farming residences/occupations with PD were examined using generalized estimating equations while controlling for age-at-examination, sex, cigarette smoking, and caffeine consumption.ResultsOverall, individuals with PD were significantly more likely to report direct pesticide application than their unaffected relatives (odds ratio = 1.61; 95% confidence interval, 1.13–2.29). Frequency, duration, and cumulative exposure were also significantly associated with PD in a dose-response pattern (p ≤ 0.013). Associations of direct pesticide application did not vary by sex but were modified by family history of PD, as significant associations were restricted to individuals with no family history. When classifying pesticides by functional type, both insecticides and herbicides were found to significantly increase risk of PD. Two specific insecticide classes, organochlorines and organophosphorus compounds, were significantly associated with PD. Consuming well-water and living/working on a farm were not associated with PD.ConclusionThese data corroborate positive associations of broadly defined pesticide exposure with PD in families, particularly for sporadic PD. These data also implicate a few specific classes of pesticides in PD and thus emphasize the need to consider a more narrow definition of pesticides in future studies.

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

“…Another population-based study also reported an increased risk with occupational exposure to herbicides (OR 3.06, 95% CI 1.34-7.00) [290]. A family-based study that found a dose-response relationship between overall pesticide exposure and PD reported an increased risk related to herbicides (OR 1.59, 95% CI 1.00-2.54) but could not examine dose-response [302].…”

“…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 family-based study that used siblings, parents and spouses as controls reported increased risk of PD with overall exposure to pesticides (OR 1.61, 95% CI 1.13-2.29) with a dose-response relationship for cumulative exposure (p for trend 0.002) [302]. The association was restricted to cases without family history of PD and significant both for insecticides and herbicides [302]. One hospital-based study reported a marginally increased risk with increasing duration of pesticide exposure [144].…”

“…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].…”

“…Of 17 studies, 9 reported increased risk of PD either for insecticides as a group, or for specific insecticides [153,154,156,290,302,306,321,322,324], with ORs ranging from 1.2 to 5.8. The other 8 studies, all mentioned above, reported no association for insecticides as a group or for specific insecticides [143,292,299,301,304,315,316,325].…”