title: Long term neurocognitive impact of low dose prenatal methylmercury exposure in Hong Kong.
abstract: BACKGROUND
  International studies suggest that low dose prenatal methylmercury exposure (>29 nmol/L) has long-term adverse neurocognitive effects. There is evidence that the majority of children in Hong Kong exceed this level as a result of high fish consumption of mothers during pregnancy.
  
  
  OBJECTIVE
  To study whether there are any associations between low-dose prenatal methylmercury exposure and neurocognitive outcomes in Hong Kong children.
  
  
  METHODS
  All 1057 children from the original birth cohort were eligible for entry into the study, except children with conditions that would affect neurocognitive development, but were unrelated to methylmercury exposure. Subjects were assessed by a wide panel of tests covering a broad range of neurocognitive functions: Hong Kong Wechsler Intelligence Scale for Children (HK-WISC), Hong Kong List Learning Test (HKLLT), Tests of Everyday Attention for Children (TEACH), Boston Naming Test, and Grooved Pegboard Test.
  
  
  RESULTS
  608 subjects were recruited (median age 8.2 years, IQR 7.3, 8.8; 53.9% boys). After correction by confounders including child age and sex, multivariate analysis showed that cord blood mercury concentration was significantly associated with three subtests: Picture Arrangement of HK-WISC (coefficient -0.944, P=0.049) and Short and Long Delay Recall Difference of the HKLLT (coefficient -1.087, P=0.007 and coefficient -1.161, P=0.005, respectively), i.e., performance worsened with increasing prenatal methylmercury exposure in these subtests.
  
  
  CONCLUSIONS
  Small, but statistically significant adverse associations between prenatal methylmercury exposure and long-term neurocognitive effects (a visual sequencing task and retention ability of verbal memory) were found in our study. These effects are compatible with findings of studies with higher prenatal methylmercury exposure levels and suggest that safe strategies to further reduce exposure levels in Hong Kong are desirable.
authors: Department of Paediatrics, Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong. hslam@cantab.net
authors: Hugh Simon
authors: HS
authors: Lam
authors: Ka Ming
authors: KM
authors: Kwok
authors: Peggy Hiu Ying
authors: PH
authors: Chan
authors: Hung Kwan
authors: HK
authors: So
authors: Albert Martin
authors: AM
authors: Li
authors: Pak Cheung
authors: PC
authors: Ng
authors: Tai Fai
authors: TF
authors: Fok
mesh_terms: D000293:Adolescent; D001519:Behavior; D002648:Child; D002675:Child, Preschool; D003072:Cognition Disorders / Q000453:epidemiology*; D004032:Diet / Q000706:statistics & numerical data; D004781:Environmental Exposure / Q000706:statistics & numerical data*; D004785:Environmental Pollutants / Q000097:blood / Q000378:metabolism*; D005260:Female; D005312:Fetal Blood / Q000378:metabolism; D006723:Hong Kong / Q000453:epidemiology; D006801:Humans; D007361:Intelligence Tests; D007858:Learning; D008297:Male; D018811:Maternal Exposure / Q000706:statistics & numerical data; D008568:Memory / Q000187:drug effects; D008628:Mercury / Q000097:blood / Q000633:toxicity; D008767:Methylmercury Compounds / Q000097:blood / Q000378:metabolism* / Q000633:toxicity; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects / Q000453:epidemiology*; D017747:Seafood / Q000706:statistics & numerical data; D014888:Wechsler Scales
chemical_list: D004785:Environmental Pollutants; D008767:Methylmercury Compounds; D008628:Mercury