Lead exposure and auditory processing: Behavioral and physiological measures.

摘要

Lead exposure affects children's intelligence indices and classroom behavior in a negative manner, and has been associated with learning disabilities, attention deficit, developmental delay, impaired cognitive performance, and poor auditory processing skills. In primates, lead exposure affects basic auditory processing skills important in speech perception. All of the studies on exposure to lead involving Auditor Brainstem Response (ABR) measures showed prolonged latencies, with increased lead levels.; This study compared behavioral and physiological measures of auditory function among children exposed and not-exposed to lead. Twenty children exposed to lead and twenty non-exposed age-matched children were included in the study. Each group consisted of ten male and ten female children, for a total of 40 subjects. All children included in the study had normal hearing sensitivity. Behavioral tests included pure tone audiometry, the SCAN, and the Binaural Fusion and Competing Sentences. Physiological tests consisted of immittance audiometry, ABR, Middle Latency Response (MLR), Late auditory evoked potentials, the P300 response, and Mismatch Negativity (MMN).; The test battery for this study yielded 41 test scores for each subject. Overall, children exposed to lead had lower average performances than non-exposed children on 26 of the 41 tests. Children exposed to lead performed significantly poorer than their non-exposed peers on the Auditory Figure Ground test. When combined, the test results showed significant differences between the groups. Wilcoxon signed ranks tests showed that children exposed to lead tended overall to score significantly lower, that significantly more exposed children scored below average, and that a significantly larger number of lead-exposed children scored more than two standard deviations below average than non-exposed children.; Cluster analysis of the data indicated that variables used in this study could place children exposed to lead and non-exposed children in two fairly distinct groups. The behavioral battery and latencies of ABR-MLR provided the most accurate grouping of children. Correlation analysis revealed some weak correlations between behavioral and physiological tests.; These findings indicate diminished auditory function among children exposed to low levels of lead, which may have implications on children's educational advancement.