Potential cognitive and motor effects from exposure to elemental mercury (Hg0) were examined in the presence and absence of a polymorphism (Val66Met) in brain-derived neurotrophic factor (BDNF). A group of 194 male dentists (DDs) and 233 female dental assistants (DAs) were occupationally exposed to mercury and had no history of kidney or nervous system disorders. Acute exposure was measured using spot urinary Hg (HgU) concentrations (average 3.32 and 1.98 μg/l, respectively) and indices of chronic occupational exposure (26.3 and 14.9 years, respectively, weighted for historical exposures). The BDNF status was 68% and 66% wild type, 26% and 30% single substitution, and 5% and 4% full mutation for DDs and DAs, respectively. DDs and DAs were evaluated separately. Regression analyses controlled for age, premorbid intelligence, alcohol consumption, and education. Statistically significant adverse associations with HgU (p <.05) were found for nine measures among DDs (Digit Span Forward, Digit and Spatial SpanBackward, Visual Reproduction, Finger Tapping Dominant, Alternate, and Alternate Partialed, Hand Steadiness, and Tracking), and eight measures among DAs (Digit SpanForward, Visual Reproduction, Pattern DiscriminationRate, Symbol Digit Rate, Trailmaking B, Finger Tapping Dominant and Alternate Partialed, and Hand Steadiness). The BDNF status was associated with four measures in DDs and three measures in DAs. Joint effects were found for Finger Tapping Alternate and Alternate Partialed in DDs and Hand Steadiness and Trailmaking B in DAs. Joint effects were additive in all cases. Performance on verbal intelligence and reaction time were not associated with either HgU or BDNF status. A test of threshold effect for the association of Hand Steadiness with HgU demonstrated no lower boundary in both DDs and DAs. No associations were observed with estimates of chronic mercury exposure. Our findings are applicable to exposure levels of the general population and identify a potentially vulnerable group with a BDNF polymorphism.
- BDNF polymorphism
- Motor function
- Short-term memory
ASJC Scopus subject areas
- Cellular and Molecular Neuroscience