The association of bone and blood manganese with motor function in Chinese workers

Manganese (Mn) is an essential element. However, Mn overexposure is associated with motor dysfunction. This cross-sectional study assessed the association between bone Mn (BnMn) and whole blood Mn (BMn) with motor function in 59 Chinese workers. BnMn and BMn were measured using a transportable in vivo neutron activation analysis system and inductively coupled plasma mass spectrometry, respectively. Motor function (manual coordination, postural sway, postural hand tremor, and fine motor function) was assessed using the Coordination Ability Test System (CATSYS) and the Purdue Pegboard. Relationships between Mn biomarkers and motor test scores were analyzed with linear regression models adjusted for age, education, current employment, and current alcohol consumption. BMn was significantly inversely associated with hand tremor intensity (dominant hand (beta=-0.04, 95 % confidence interval (CI):-0.07,-0.01; non-dominant hand beta=-0.05, 95 % CI:-0.08,-0.01) hand tremor center frequency (non-dominant hand beta=-1.61, 95 % CI:-3.03,-0.19) and positively associated with the Purdue Pegboard Assembly Score (0 = 4.58, 95 % CI:1.08, 8.07). BnMn was significantly inversely associated with finger-tapping performance (non-dominant hand beta=-0.02, 95 % CI:-0.04,-0.004), mean sway (eyes closed and foam beta=-0.68, 95 % CI:-1.31,-0.04), and positively associated with hand tremor center frequency (dominant hand, beta = 0.40, 95 % CI:0.002, 0.80). These results suggest BMn is related to better postural hand tremor and fine motor control and BnMn is related to worse motor coordination and postural hand tremor but better (i.e., less) postural sway. The unexpected positive results might be explained by choice of biomarker or confounding by work-related motor activities. Larger, longitudinal studies in this area are recommended.

Automated summary

This study investigated the association between manganese and motor function in Chinese workers. The results showed that blood manganese was negatively associated with hand tremor intensity and frequency, and positively associated with Purdue Pegboard Assembly Score. On the other hand, bone manganese was negatively associated with finger-tapping performance and mean sway, and positively associated with hand tremor frequency. These findings suggest that blood manganese is related to better postural hand tremor and fine motor control, while bone manganese is related to worse motor coordination and hand tremor but less postural sway.