Potential neuropsychological profiles in welders occupationally exposed to manganese: An examination of effect size patterns

Abstract

This study used effect sizes to examine two recently published articles by Bowler et al. (2003, 2006) that purport to show that welders who had been occupationally exposed to manganese demonstrate a specific pattern of neuropsychological impairment. In the two articles, the welding groups were composed of different participants, but the control group was composed of the same participants in both studies. A similar neuropsychological battery was administered across studies. Effect size differences between welders and controls were quite different across both studies, and the pattern of effect sizes within each study for neuropsychological domains was different. Taken together, these articles do not support the claim that chronic manganese exposure in welders results in a specific and identified pattern of neuropsychological impairment.

Neurobehavioral Deficits and Parkinsonism in Occupations with Manganese Exposure: A Review of Methodological Issues in the Epidemiological Literature

“…Rohling and Demakis [66] compared the two case series by Bowler et al [47,64] and reported that the estimated neuropsychological effect sizes and the patterns of effects within each study were different, concluding that the two studies do not support a common pattern of neuropsychological impairment attributable to Mn exposure. Rohling and Demakis [66] required two unsupported assumptions: (1) that the studies had the same valid designs for quantitative etiologic inference; and (2) that the exposure experience (duration, air concentrations, types of welding), was similar.…”

“…Rohling and Demakis [66] required two unsupported assumptions: (1) that the studies had the same valid designs for quantitative etiologic inference; and (2) that the exposure experience (duration, air concentrations, types of welding), was similar. Moreover, the Rohling and Demakis analyses reveal considerable consistency in deficits in the Bowler studies, although the series by Bowler et al [64] exhibited systematically higher levels of deficit.…”

The inhibitory effect of manganese on acetylcholinesterase activity enhances oxidative stress and neuroinflammation in the rat brain

“…Studies in humans and animals indicate that excessive Mn exposure is associated with behavioral changes and altered cognitive function (Rohling and Demakis, 2007; Bouchard, et al, 2008). Mn-induced cortical cholinergic dysfunction is compatible with these cognitive de cits, as well as with the dementia observed later on in the clinical course of manganism (Finkelstein et al, 2007).…”

Evaluation of neurobehavioral and neuroinflammatory end-points in the post-exposure period in rats sub-acutely exposed to manganese

“…The initial neurobehavioral symptoms are nonspecific (Mergler, 1999; Verhoeven et al, 2011), as the initial neurobehavioral symptoms may progress to a parkinsonian-like disorder characterized by tremor, bradykinesia and rigidity (Calne et al, 1994; Pal et al, 1999). The diagnosis of manganism is commonly made in the late phases of the disease after the appearance of the parkinsonian symptoms (Alves et al, 1997; Fell et al, 1996; Kim et al, 2009; Reynolds et al, 1994; Rohling and Demakis, 2007; Sadek et al, 2003) by determination of whole blood (WB) and urine Mn levels (Fitzgerald et al, 1999; Nagatomo et al, 1999; Takagi et al, 2002) and increased signal intensity in T1-weighted magnetic resonance (MR) images (Finkelstein et al, 2008; Mirowitz et al, 1991). Although WB Mn analysis is the preferred screening method, the high variability in normal Mn levels (4.2 to 16.5 μg/L in WB and 0.40 to 0.85 μg/L in serum) (Jankovic, 2005), render it inadequate for individual biological monitoring (Apostoli et al, 2000).…”