Executive function modifies the relationship between occupational lead exposure and complex figure test performance

To determine if chronic lead exposure is associated with non-verbal memory performance and if this association is affected by organisation strategies, a component of executive functions.

We administered the Rey-Osterrieth Complex Figure (ROCF) test, both copy (ROCF-C) and 30-min delayed recall (ROCF-DR), to 358 current lead smelter workers with a mean (SD) age of 41 (9.1) years, education of 11 (2.7) years, and working lifetime-weighted average blood lead (TWA) of 39 (12.0) μg/dl. Copy and delay organisation scores, surrogates for executive functions, were developed for ROCF-C and ROCF-DR. We used multiple regression analyses to examine the relationship between TWA and ROCF performance, organisational scores, and the interaction of organisational scores and TWA after adjusting for relevant covariates.

Organisational scores, while not associated with years of education, were significantly correlated with ROCF-C and ROCF-DR performance. We found a significant relationship between TWA and ROCF-DR but not with ROCF-C performance. The interactions of TWA by copy organisation and TWA by delay organisation were significant for ROCF-DR with a significant dose-effect relationship only in participants with lower organisational scores.

Chronic lead exposure was significantly associated with complex figure test delayed recall but not copy performance. Organisational strategies, a component of executive functions, served as effect modifiers of the relationship between lead exposure and non-verbal memory. With increasing TWA exposure workers with good organisational strategies maintained performance on the complex figure test while workers with poor organisational strategies demonstrated decreasing performance.