Methylmercury and neurodevelopment: longitudinal analysis of the Seychelles child development cohort.
BACKGROUND
The Seychelles Child Development Study (SCDS) has been longitudinally following a cohort of over 700 children enrolled in 1989. Their mothers consumed a diet high in fish during pregnancy. Repeated examination of the SCDS cohort at six different ages through age 11 years has shown no pattern of adverse effects. Some early appearing beneficial associations between both prenatal and postnatal hair MeHg and several child development endpoints were noted. We hypothesized these might be related to micronutrients in the fish, but they were not found when the children reached middle school age. These findings suggest that the associations observed between MeHg and developmental outcomes may vary with developmental stage.


METHODS
We examined the main cohort of the SCDS to determine if this might be true using a longitudinal multiple regression analysis design that focused on those endpoints that were repeatedly measured at different ages. The primary endpoint analyzed was global cognition, involving a measure of developmental quotient or IQ. Secondary analyses included other domains such as Reading and Mathematics scholastic achievement, social behavior, and memory. Analyses involved two different approaches, one including incorporation of a passage of time variable, the other including a difference of scores across time points.


RESULTS
No significant associations were found between prenatal MeHg exposure and any of the repeatedly measured endpoints.


CONCLUSIONS
These results suggest that even when individual subject variance is controlled there was no consistent pattern of associations between child development outcomes and prenatal exposures to MeHg from maternal consumption of a diet high in fish. The Seychellois diet contains about 10 times more ocean fish than is typically consumed by US citizens. Our primary focus on IQ should further inform growing scientific interest in the analysis of the risks and benefits of fish consumption on overall cognitive ability.
Davidson
Philip W
PW
The Department of Pediatrics, University of Rochester School of Medicine and Dentistry, Rochester, New York, 14642, USA. phil_davidson@urmc.rochester.edu <phil_davidson@urmc.rochester.edu>
Myers
Gary J
GJ
Cox
Christopher
C
Wilding
Gregory E
GE
Shamlaye
Conrad F
CF
Huang
Li Shan
LS
Cernichiari
Elsa
E
Sloane-Reeves
Jean
J
Palumbo
Donna
D
Clarkson
Thomas W
TW
D002648:Child; D002657:Child Development / Q000187:drug effects*; D003071:Cognition / Q000187:drug effects*; D015331:Cohort Studies; D005260:Female; D005506:Food Contamination / Q000032:analysis*; D006197:Hair / Q000737:chemistry; D006801:Humans; D008297:Male; D008767:Methylmercury Compounds / Q000032:analysis / Q000506:poisoning*; D009483:Neuropsychological Tests; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects; D011978:Receptors, Nicotinic / Q000378:metabolism; D017747:Seafood; D012750:Seychelles; D013997:Time Factors
D008767:Methylmercury Compounds; D011978:Receptors, Nicotinic