Hydrocarbon exposure and Parkinson's disease

Background: Single cases of parkinsonism have been associated with hydrocarbon solvents. Objective: To determine whether exposure to hydrocarbon solvents is related to PD. Methods: Cohort study of 990 patients with PD according to Core Assessment Program for Intracerebral Transplantations (CAPIT) criteria, selected from 1455 consecutive subjects presenting at a referral center; case-control study assessing Unified PD Rating Scale scores (motor score as primary endpoint) in all subjects with positive history of hydrocarbon solvent exposure (n = 188), matched for duration of disease and gender to 188 subjects selected from the remaining 802 with a negative history. Two subgroups in the case-control study included the following: 1) response to apomorphine (n = 26); 2) brain MRI (n = 15). PET imaging (n = 9) was compared with that of historic controls. Results: Exposed patients were younger (61.0 ± 9.4 versus 64.7 ± 9.4 years, p = 0.002), predominantly male (76.4% versus 45.2%, p = 0.0001), less educated (8.4 ± 4.2 versus 10.1 ± 4.4 years, p = 0.0001), and younger at onset of disease (55.2 ± 9.8 versus 58.6 ± 10 years, p = 0.014). Exposure to hydrocarbon solvents directly correlated to disease severity (r = 0.311) and inversely correlated to latency period (r = -0.252). Nine blue-collar occupations accounted for 91.1% of exposures. Conclusions: Occupations involving the use of hydrocarbon solvents are a risk factor for earlier onset of symptoms of PD and more severe disease throughout its course. Hydrocarbon solvents may be involved in the etiopathogenesis of PD, which does not have a major genetic component.