Neurocognitive Screening of Lead-Exposed Andean Adolescents and Young Adults

Abstract

This study was designed to assess the utility of two psychometric tests with putative minimal cultural bias for use in field screening of lead (Pb)-exposed Ecuadorian Andean workers. Specifically, the study evaluated the effectiveness in Pb-exposed adolescents and young adults of a nonverbal reasoning test standardized for younger children, and compared the findings with performance on a test of auditory memory. The Raven Coloured Progressive Matrices (RCPM) was used as a test of nonverbal intelligence, and the Digit Span subtest of the Wechsler IV intelligence scale was used to assess auditory memory/attention. The participants were 35 chronically Pb-exposed Pb-glazing workers, aged 12–21 yr. Blood lead (PbB) levels for the study group ranged from 3 to 86 μg/dl, with 65.7% of the group at and above 10 μg/dl. Zinc protoporphyrin heme ratios (ZPP/heme) ranged from 38 to 380 μmol/mol, with 57.1% of the participants showing abnormal ZPP/heme (>69 μmol/mol). ZPP/heme was significantly correlated with PbB levels, suggesting chronic Pb exposure. Performance on the RCPM was less than average on the U.S., British, and Puerto Rican norms, but average on the Peruvian norms. Significant inverse associations between PbB/ZPP concentrations and RCPM standard scores using the U.S., Puerto Rican, and Peruvian norms were observed, indicating decreasing RCPM test performance with increasing PbB and ZPP levels. RCPM scores were significantly correlated with performance on the Digit Span test for auditory memory. Mean Digit Span scale score was less than average, suggesting auditory memory/attention deficits. In conclusion, both the RCPM and Digit Span tests were found to be effective instruments for field screening of visual-spatial reasoning and auditory memory abilities, respectively, in Pb-exposed Andean adolescents and young adults.

Acknowledgements

This study was conducted under the auspices of Universidad San Francisco de Quito Medical School in Quito, Ecuador. The authors thank Dr. Enrique Noboa, Dean of the College of Health Sciences, Universidad San Francisco de Quito; Dr. José Izurieta, Director of Health, Cotopaxi Province; Dr. Galo Tapia, Director of Pujilí Hospital; Dr. Cecilia Zambrano, Director of La Victoria Subcentro de Salud; Gladys Pacheco, nurse, Subcentro de Salud, La Victoria; and Universidad San Francisco de Quito Medical School for continued support of this project. The authors are also grateful to Dr. Nader Rifai, Patricia Nolan Hoover, Aruna Rabari, and Gary Bradwin of the Department of Laboratory Medicine, Children's Hospital Boston, for generous laboratory support. The authors thank Anthony B. Jacobs for his continued excellent technical support. Lauren Kessler, Gabriela Aguirre, Manuela Dousdebés, and Rosana Terán are thanked for exceptional technical assistance in the field. The authors are grateful to the David Rockefeller Center for Latin American Studies at Harvard and its director, Dr. Merilee Grindle, for support of this project. Dr. David Rosenthal and Benedict J. DiRusso, Jr., RPh, of the Harvard University Health Services are thanked for their support. The authors thank Dr. Harry Mackay of the University of Massachusetts Medical School/Shriver Center for review of the article and helpful suggestions. The authors thank the Harvard Biological Laboratories for support.