Our new paper is published online: Cognitive deficits at age 22 years associated with prenatal exposure to methylmercury


Prenatal exposure to mercury has been associated with adverse effects on child neurodevelopment.
The present study aims to determine the extent to which methylmercuryassociated
cognitive deficits persist into adult age. In a Faroese birth cohort originally
formed in 1986 – 1987 (N = 1,022), prenatal methylmercury exposure was assessed in terms
of the mercury concentration in cord blood and maternal hair. Clinical examinations of 847
cohort members at age 22 years were carried out in 2008 – 2009 using a panel of neuropsychological
tests that reflected major functional domains. Subjects with neurological
and psychiatric diagnoses were excluded from the data analysis, thus leaving 814 subjects.
Multiple regression analysis included covariates previously identified for adjustment.
Deficits in Boston Naming Test (BNT) and other tests of verbal performance were significantly
associated with the cord-blood mercury concentration. Deficits were also present in
all other tests applied, although most were not statistically significant. Structural equation
models were developed to ascertain the possible differences in vulnerability of specific
functional domains and the overall association with general intelligence. In models for
individual domains, all of them showed negative associations, with crystallized intelligence
being highly significant. A hierarchical model for general intelligence based on all
domains again showed a highly significant negative association with the exposure, with an
approximate deficit that corresponds to about 2.2 IQ points at a 10-fold increased prenatal
methylmercury exposure. Thus, although the cognitive deficits observed were smaller than
at examinations at younger ages, maternal diets with contaminated seafood were associated
with adverse effects in this birth cohort at age 22 years. The deficits affected major
domains of brain functions as well as general intelligence. Thus, prenatal exposure to this
marine contaminant appears to cause permanent adverse effects on cognition.