Introduction Previous studies have reported a dose-response relationship between occupational manganese (Mn) exposure and decreased motor function, adverse psychological symptoms, attention deficits, and working memory deficits. Residential exposure to Mn has also been associated with depression and anxiety but the relationship with environmental Mn exposure and motor and cognitive function is unclear. Many studies have shown cognitive dysfunction in children and adults exposed to environmental Mn, and there is some evidence implicating environmental exposure to Mn as a risk factor for Parkinson Disease.

Objective We conducted a pilot study to assess the feasibility of motor and cognitive assessments for a community-based study of the effects of environmental Mn exposure in adults.

Methods A convenience sample of 100 adult residents, aged 40 years or older, from a community in close proximity to a Mn smelter in South Africa was assessed, excluding those with a pre-existing neurologic disorder that would preclude completion of testing. Assessments comprised a demographic questionnaire that included residential, medical, and occupational histories; the Beck Depression Inventory; the State-Trait Anxiety Inventory; Unified Parkinson Disease Rating Scale motor subsection part 3 (UPDRS3) to assess parkinsonism, the clinical signs of Parkinson Disease; the Grooved Pegboard;. and two cognitive control tasks (the Go-No-Go, and Letter Number Sequencing). For this pilot study, we investigated the prevalence of parkinsonism defined as a UPDRS3 score ≥ 15, and the correlation between motor function and cognitive control.

Results We found a high prevalence of parkinsonism using the UPDRS3 (18%), a high prevalence of anxiety and depression, and strong correlations between the UPDRS3 and both motor and cognitive control tasks (p < 0.0001).

Conclusion Motor dysfunction appears to be associated with cognitive dysfunction in this small sample. A larger study is underway to confirm these findings.