Possible environmental, occupational, and other etiologic factors for Parkinson's disease

Abstract

In a case-control study, we investigated the possible etiologic relevance to Parkinson's disease (PD) of rural factors such as farming activity, pesticide exposures, well-water drinking, and animal contacts; toxicologic exposures such as wood preservatives, heavy metals, and solvents; general anesthesia; head trauma; and differences in the intrauterine environment. We recruited 380 patients in nine German clinics, 379 neighborhood control subjects, and 376 regional control subjects in the largest case-control study investigating such factors and collected data in structured personal interviews using conditional logistic regression to control for educational status and cigarette smoking. The latter was strongly inversely associated with PD. There were significantly elevated odds ratios (OR) for pesticide use, in particular, for organochlorines and alkylated phosphates, but no association was present between PD and other rural factors. A significantly elevated OR was present for exposure to wood preservatives. Subjective assessment by the probands indicated that exposure to some heavy metals, solvents, exhaust fumes, and carbon monoxide was significantly more frequent among patients than control subjects, but this was not confirmed by a parallel assessment of job histories according to a job exposure matrix. Patients had undergone general anesthesia and suffered severe head trauma more often than control subjects, but a dose-response gradient was not present. Patients reported a significantly larger number of amalgam-filled teeth before their illness than control subjects. The frequency of premature births and birth order did not differ between patients and control subjects. Patients reported significantly more relatives affected with PD than control subjects. These results support a role for environmental and genetic factors in the etiology of PD.

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].…”

“…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].…”

“…Among studies that found an increased risk, one hospital-based study reported increased risk of PD with overall herbicide use (OR 1.7, 95 % CI 1.0-2.7) and a trend with longer duration of exposure using regional controls (p for trend 0.001) but not using neighborhood controls [154].…”

“…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].…”

“…One of the "positive" studies was the hospital-based study mentioned above [154] that, similar to herbicides, found a dose-response relationship for exposure to insecticides using regional controls (p for trend 0.001) but not using neighborhood controls. Although estimates were unstable, there was an increased risk associated with organochlorines using regional controls (OR 5.8, 95% CI 1.1-30.1) but not using neighborhood controls [154].…”