title: Differential effects of lead exposure on components of verbal memory.
abstract: OBJECTIVE
  To determine if verbal learning and memory requiring acquisition and retention of information is differentially affected by lead exposure.
  
  
  METHODS
  The Rey Auditory Verbal Learning Test (RAVLT), a test of verbal learning and memory, was administered to 256 English speaking lead smelter workers who had a mean (SD) age of 41 (9.4) years and employment duration of 17 (8.1) years. Lead exposure variables, based on up to 25 years of prior blood lead data, included a mean (SD) current blood lead (PbB) of 28 (8.8) microg/dl, working lifetime time weighted average blood lead (TWA) of 39 (12.3) microg/dl, and working lifetime integrated blood lead index (IBL) of 728 (434.4) microg-y/dl. Associations of these chronic and recent lead exposure variables with measures from the RAVLT were modelled through multiple linear regressions after controlling for age and educational achievement.
  
  
  RESULTS
  PbB was not associated with any of the RAVLT variables. However, TWA and IBL contributed significantly to the explanation of variance of measures of encoding/storage and retrieval but not to immediate memory span, attention, and learning. Grouping study participants by RAVLT performance according to three recognised clinical memory paradigms showed significantly higher TWA and IBL in the group with "generalised memory impairment" after adjusting for age and educational achievement. We examined recall mechanisms in each group by serial position in the word list and found stronger primacy (recall of words from the beginning of the list) in the "no impairment" and "retrieval difficulties" groups while the "generalised memory impairment" group had better performance on recency (recall of words from the end of the list).
  
  
  CONCLUSIONS
  Lead exposure over years and not PbB interfered with the organisation and recall of previously learned verbal material. Chronic lead exposure affects encoding/storage and retrieval of verbal information.
authors.affiliation: Center for Occupational and Environmental Neurology, 3901 Greenspring Ave., Suite 101, Baltimore, Maryland 21211, USA. coen@msn.com
authors.forename: M L
authors.initials: ML
authors.lastname: Bleecker
authors.forename: D P
authors.initials: DP
authors.lastname: Ford
authors.forename: K N
authors.initials: KN
authors.lastname: Lindgren
authors.forename: V M
authors.initials: VM
authors.lastname: Hoese
authors.forename: K S
authors.initials: KS
authors.lastname: Walsh
authors.forename: C G
authors.initials: CG
authors.lastname: Vaughan
mesh_terms: D000328:Adult; D000375:Aging / Q000523:psychology; D004522:Educational Status; D004784:Environmental Monitoring / Q000379:methods; D006801:Humans; D007854:Lead / Q000097:blood; D020265:Lead Poisoning, Nervous System, Adult / Q000097:blood / Q000523:psychology*; D008297:Male; D008569:Memory Disorders / Q000097:blood / Q000139:chemically induced* / Q000175:diagnosis; D011939:Mental Recall / Q000187:drug effects; D008669:Metallurgy; D008875:Middle Aged; D009483:Neuropsychological Tests; D009784:Occupational Diseases / Q000097:blood / Q000139:chemically induced*; D016273:Occupational Exposure / Q000032:analysis; D014706:Verbal Learning / Q000187:drug effects
chemical_list: D007854:Lead
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