title: Critical windows of exposure for arsenic-associated impairment of cognitive function in pre-school girls and boys: a population-based cohort study.
abstract: BACKGROUND
  Exposure to arsenic through drinking water has been associated with impaired cognitive function in school-aged children in a few cross-sectional studies; however, there is little information on critical windows of exposure.
  
  
  METHODS
  We conducted a population-based longitudinal study in rural Bangladesh. We assessed the association of arsenic exposure, based on urinary arsenic (U-As; twice during pregnancy and twice in childhood), with the development of about 1700 children at 5 years of age using Wechsler Pre-school and Primary Scale of Intelligence [intelligence quotient (IQ)].
  
  
  RESULTS
  Median maternal U-As in pregnancy was 80 µg/l (10-90 percentiles: 25-400 µg/l). Children's urine contained 35 (12-155) µg/l and 51 (20-238) µg/l at 1.5 and 5 years, respectively. Using multivariable-adjusted regression analyses, controlling for all potential confounders and loss to follow-up, we found that verbal IQ (VIQ) and full scale IQ (FSIQ) were negatively associated with (log) U-As in girls. The associations were consistent, but somewhat stronger with concurrent arsenic exposure [VIQ: B = -2.4, 95% confidence interval (CI) = -3.8 to -1.1; FSIQ: B = -1.4, 95% CI = -2.7 to -0.1, n = 817), compared with that at 1.5 years (VIQ: B = -0.85, 95% CI = -2.1 to 0.4; FSIQ: B = -0.74, 95% CI = -1.9 to 0.4, n = 902), late gestation (VIQ: B = -1.52, 95% CI = -2.6 to -0.4; FSIQ: B = -1.35, 95% CI = -2.4 to -0.3, n = 874) and early gestation (VIQ: B = -1.23, 95% CI = -2.4 to -0.06; FSIQ: B = -0.92, 95% CI = -2.0 to -0.2, n = 833). In boys, U-As showed consistently low and non-significant associations with all IQ measures. An effect size calculation indicated that 100 µg/l U-As was associated with a decrement of 1-3 points in both VIQ and FSIQ in girls.
  
  
  CONCLUSIONS
  We found adverse effects of arsenic exposure on IQ in girls, but not boys, at 5 years of age.
authors.affiliation: International Center for Diarrhoeal Disease Research, Dhaka, Bangladesh. jena@icddrb.org
authors.forename: J D
authors.initials: JD
authors.lastname: Hamadani
authors.forename: F
authors.initials: F
authors.lastname: Tofail
authors.forename: B
authors.initials: B
authors.lastname: Nermell
authors.forename: R
authors.initials: R
authors.lastname: Gardner
authors.forename: S
authors.initials: S
authors.lastname: Shiraji
authors.forename: M
authors.initials: M
authors.lastname: Bottai
authors.forename: S E
authors.initials: SE
authors.lastname: Arifeen
authors.forename: S N
authors.initials: SN
authors.lastname: Huda
authors.forename: M
authors.initials: M
authors.lastname: Vahter
mesh_terms: D001151:Arsenic / Q000633:toxicity* / Q000652:urine; D020261:Arsenic Poisoning / Q000150:complications / Q000453:epidemiology* / Q000652:urine; D001459:Bangladesh / Q000453:epidemiology; D001837:Body Weights and Measures; D002657:Child Development / Q000187:drug effects; D015362:Child Nutrition Disorders / Q000150:complications / Q000453:epidemiology; D002675:Child, Preschool; D003072:Cognition Disorders / Q000139:chemically induced* / Q000652:urine; D004781:Environmental Exposure / Q000009:adverse effects* / Q000032:analysis / Q000706:statistics & numerical data; D005260:Female; D006306:Health Surveys; D006801:Humans; D007223:Infant; D007360:Intelligence / Q000187:drug effects; D007361:Intelligence Tests; D008137:Longitudinal Studies; D008297:Male; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects / Q000139:chemically induced / Q000453:epidemiology / Q000652:urine; D012737:Sex Factors; D012959:Socioeconomic Factors; D014874:Water Pollutants, Chemical / Q000633:toxicity* / Q000652:urine; D014881:Water Supply
chemical_list: D014874:Water Pollutants, Chemical; D001151:Arsenic