Occupational and environmental risk factors for Parkinson's disease
Case-control study or prevalent parkinsonism and PD cases in Grampian and Easter Ross, Scotland. Cases were defined using United Kingdom Parkinson's Disease Society Brain Bank clinical diagnostic criteria. Dementia, cerebrovascular and drug-induced cases were excluded. Age and gender-balanced controls were drawn from hospital outpatients and the community. Trained interviewers administered a questionnaire regarding lifestyle and occupation including solvent, pesticide and metal exposure (iron, copper, manganese). An occupational hygienist estimated metal exposures blind to disease status using a job exposure matrix modified by subjective exposure estimation. Lifetime occupational histories were classified by occupational (Dictionary of Occupational Titles) and industry (modified International Standard Industrial Classification. A follow-up postal study in Grampian enquired about tea and coffee consumption, anxiolytic, anti-depressant and hypnotic use and head injury. 202 cases and 420 controls were recruited between June 2000 and July 2002 (responsive rate 46.2%). Multiple logistic regression analyses showed first-degree family history of PD (OR 4.12, 95%CI 1.92-8.83) and pesticides ('high' exposure OR 1.69, 95% CI 1.06-2.69) were risk factors. Smoking was protective (OR 0.26, 95%CI 0.18-0.29) with an exposure-response relationship. Both occupational and industry coding systems showed non-significantly increased risks for 'agriculture'. The follow-up study response rate was 93% (149 cases, 305 controls). Tea and coffee consumption were not associated with PD. A positive association of use of psychoactive medication with PD was probably explained by their use after disease onset. A non-significantly increased association of head injury and PD was not supported by the follow-up postal study. First-degree family history of PD was associated with PD. Pesticide use was a risk factor for PD, whereas smoking was associated with reduced risk. The increased risk for agriculture may reflect pesticide use.