PT  - JOURNAL ARTICLE
AU  - M L Bleecker
AU  - D P Ford
AU  - K N Lindgren
AU  - V M Hoese
AU  - K S Walsh
AU  - C G Vaughan
TI  - Differential effects of lead exposure on components of verbal memory
AID  - 10.1136/oem.2003.011346
DP  - 2005 Mar 01
TA  - Occupational and Environmental Medicine
PG  - 181--187
VI  - 62
IP  - 3
4099  - http://oem.bmj.com/content/62/3/181.short
4100  - http://oem.bmj.com/content/62/3/181.full
SO  - Occup Environ Med2005 Mar 01; 62
AB  - Aims: 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) μg/dl, working lifetime time weighted average blood lead (TWA) of 39 (12.3) μg/dl, and working lifetime integrated blood lead index (IBL) of 728 (434.4) μg-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.