Blood lead levels and cognitive functioning: A meta-analysis

Thomas Vlasak; Galateja Jordakieva; Timo Gnambs; Christoph Augner; Richard Crevenna; Robert Winker; Alfred Barth

doi:10.1016/j.scitotenv.2019.03.052

Blood lead levels and cognitive functioning: A meta-analysis

Sci Total Environ. 2019 Jun 10:668:678-684. doi: 10.1016/j.scitotenv.2019.03.052. Epub 2019 Mar 5.

Authors

Thomas Vlasak¹, Galateja Jordakieva², Timo Gnambs³, Christoph Augner⁴, Richard Crevenna², Robert Winker⁵, Alfred Barth⁶

Affiliations

¹ Institute for Psychology, Sigmund Freud University Linz, Linz, Austria.
² University Department of Physical Medicine, Rehabilitation and Occupational Medicine, Medical University of Vienna, Vienna, Austria.
³ Leibniz-Institute for Educational Trajectories, Bamberg, Germany; Institute of Education and Psychology, Johannes Keppler University Linz, Linz, Austria.
⁴ IGGMB-Health Research Institute, University Clinics of the Paracelsus Medical University, Salzburg, Austria.
⁵ Health and Prevention Center of the Insurance Institution for the Vienna Employee, Vienna, Austria.
⁶ Institute for Psychology, Sigmund Freud University Linz, Linz, Austria. Electronic address: aflred.barth@sfu.ac.at.

PMID: 30856576
DOI: 10.1016/j.scitotenv.2019.03.052

Abstract

Objective: The neurotoxicity of lead is well-known and even low exposure levels potentially impact neurocognitive abilities. This metaanalysis aimed to investigate associations between neurocognitive performance and lead exposure in adults and further assess potential effect thresholds.

Material and methods: Articles indexed in Medline published until January 2017 reporting associations between lead exposure, blood lead, cognitive abilities and sensomotoric performance were included. The unbiased, standardized mean differences g between lead exposure and control groups extracted from the primary studies were pooled using a three-level, random-effects meta-analytic model with a restricted maximum likelihood estimator. Moderator analyses were conducted using weighted, mixedeffects regression analyses.

Results: We identified 22 articles (n=3,849 participants, mean age 39.94±7.87years) published between 1976 and 2014 reporting lead exposure effects on cognitive and sensomotoric parameters (verbal abilities, visuospatial abilities, memory, attention, psychomotor function). On average, blood lead concentrations were 21.09±6.44 μg/dl higher in exposed than in control subjects. After exclusion of outliers, the random-effects three-level meta-analysis identified a significant (p<.001) pooled mean difference between exposure and control groups. Except for a smaller effect in the digit symbol test (p<.05), lead exposure did not result in different outcomes across the examined cognitive measures. Based on a marginally significant (p=.06) effect of difference in exposure levels, a blood lead increase of 10 μg/dl translated into a decline in cognitive abilities of Hedges g=.09.

Conclusions: Neurocognitive performance in adults with occupational or environmental lead exposure was significant impaired with regard to the examined parameters. However, further studies are needed for the determination of effect thresholds and reversibility.

Keywords: Attention; Cognition; Lead exposure; Memory; Meta-analysis; Occupational health.

Publication types

Meta-Analysis

MeSH terms

Adult
Cognition
Environmental Exposure / statistics & numerical data*
Environmental Pollutants / blood*
Female
Humans
Lead / blood*
Male
Middle Aged
Psychomotor Performance

Substances

Environmental Pollutants
Lead