Clinical course of neuropsychological functioning after chronic exposure to organic and inorganic lead

This case series describes the clinical course (12- to 28-month follow-up) of neuropsychological functioning in 23 workers who had chronic occupational exposure to a mixture of organic and inorganic lead. Significant improvement in performance was seen in 1/23 tests and deterioration in 3/23 tests. However, there was no significant change in the majority of tests (19/23). Tests that showed deterioration were all tests of psychomotorlmotor speed. In addition, 10 of 13 workers who completed a symptom checklist twice reported more frequent physical, cognitive, and affective symptoms at follow-up. This increase in symptoms was associated with psychomotorlmotor slowing as compared to initial test performance. Many workers subjectively reported an increased frequency of memory and concentration problems at follow-up, although this change could not be documented objectively. Individual worker demographic and exposure characteristics were not predictive of changes in neuropsychological performance at retest. We propose a psychosocial mechanism to explain the increase in symptom severity and the psychomotorlmotor slowing because environmental levels of lead declined during the inter-test interval.