Differential effects of lead exposure on components of verbal memory.
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.
Bleecker
M L
ML
Center for Occupational and Environmental Neurology, 3901 Greenspring Ave., Suite 101, Baltimore, Maryland 21211, USA. coen@msn.com
Ford
D P
DP
Lindgren
K N
KN
Hoese
V M
VM
Walsh
K S
KS
Vaughan
C G
CG
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
D007854:Lead
J Clin Psychol. 1993 Nov;49(6):883-90
8300877
Nat Neurosci. 2003 Jan;6(1):90-5
12483214
Br J Ind Med. 1989 Oct;46(10):698-707
2818958
Br J Ind Med. 1984 Aug;41(3):352-61
6743583
Environ Health Perspect. 2002 Feb;110(2):133-8
11836140
J Toxicol Clin Toxicol. 1989;27(1-2):37-51
2788750
J Clin Psychol. 1980 Oct;36(4):1009-12
7440727
J Clin Psychol. 1989 Mar;45(2):277-80
2723084
J Clin Psychol. 1984 May;40(3):785-7
6746989
Arch Clin Neuropsychol. 1991;6(4):241-9
14589516
Psychol Bull. 1977 Nov;84(6):1130-49
928573
Arch Clin Neuropsychol. 1993 Mar;8(2):123-35
14589670
Int Arch Occup Environ Health. 1978 Jul 14;41(4):217-36
355147
J Clin Neuropsychol. 1983 Dec;5(4):337-44
6643687
J Occup Environ Med. 1997 May;39(5):426-31
9172087
Environ Res. 1993 Jul;62(1):125-47
8325258
Neurotoxicology. 2003 Aug;24(4-5):625-31
12900075
Neurotoxicol Teratol. 1998 Jan-Feb;20(1):19-27
9511166
J Clin Psychol. 1991 May;47(3):351-7
2066402
Neurology. 1997 Mar;48(3):639-45
9065540
J Clin Psychol. 1988 May;44(3):403-11
3384968
Percept Mot Skills. 1991 Oct;73(2):539-50
1766784
Scand J Work Environ Health. 1978 Dec;4(4):295-303
734390
Science. 2003 Jan 24;299(5606):577-80
12543980
Am J Epidemiol. 1993 May 1;137(9):1006-21
8317446
Occup Environ Med. 1998 Mar;55(3):202-9
9624272
J Occup Environ Med. 2002 Jun;44(6):574-8
12085485
Occup Environ Med. 1995 Jan;52(1):2-12
7697135
Occup Environ Med. 1996 Jul;53(7):472-7
8704872
J Consult Clin Psychol. 1983 Dec;51(6):848-55
6655101
Int J Neurosci. 1992 May-Jun;64(1-4):177-81
1342037
Int Arch Occup Environ Health. 1984;53(3):233-46
6706419
Neurology. 1999 May 12;52(8):1610-7
10331686