Manganese exposure, parkinsonian signs, and quality of life in South African mine workers

Background: Manganese (Mn) neurotoxicity is associated with parkinsonism; the associated motor deficits can affect individuals’ quality of life (QoL). We investigated associations between Mn exposure, parkinsonian signs, and QoL in Mn mine workers. Methods: We assessed parkinsonian signs and QoL in 187 black South African Mn mine workers, using the Unified Parkinson Disease Rating Scale motor subsection 3 (UPDRS3) and the Parkinson Disease Questionnaire (PDQ-39), respectively. We estimated cumulative Mn exposure in mg Mn/m³-years using complete occupational histories and a job-exposure matrix. We investigated the cross-sectional association between cumulative Mn exposure and UPDRS3 score, and the UPDRS3 score and PDQ-39, adjusting for age, using linear regression. Results: Participants’ mean age was 41.8 years (range, 21-67 years); 97.3% were male. Estimated mean cumulative Mn exposure at the time of examination was 5.4 mg Mn/m³-years, with a mean of 14.0 years working in a Mn mine. The mean UPDRS3 score was 10.1 and 25.7% of the workers had a UPDRS3 score greater than or equal to 15. There was a U-shaped dose-response relation between cumulative Mn exposure and UPDRS3 score, with a positive association up to 15 mg Mn/m³-years of exposure and an inverse association thereafter. Greater UPDRS3 scores were associated with poorer self-reported QoL. Conclusion: In this cohort of employed Mn mine workers, parkinsonian signs were common and were associated with both estimated cumulative Mn exposure and poorer QoL.