title: Association of Childhood Blood Lead Levels With Cognitive Function and Socioeconomic Status at Age 38 Years and With IQ Change and Socioeconomic Mobility Between Childhood and Adulthood.
abstract: Many children in the United States and around the world are exposed to lead, a developmental neurotoxin. The long-term cognitive and socioeconomic consequences of lead exposure are uncertain.
  
  
  
  To test the hypothesis that childhood lead exposure is associated with cognitive function and socioeconomic status in adulthood and with changes in IQ and socioeconomic mobility between childhood and midlife.
  
  
  
  A prospective cohort study based on a population-representative 1972-1973 birth cohort from New Zealand; the Dunedin Multidisciplinary Health and Development Study observed participants to age 38 years (until December 2012).
  
  
  
  Childhood lead exposure ascertained as blood lead levels measured at age 11 years. High blood lead levels were observed among children from all socioeconomic status levels in this cohort.
  
  
  
  The IQ (primary outcome) and indexes of Verbal Comprehension, Perceptual Reasoning, Working Memory, and Processing Speed (secondary outcomes) were assessed at age 38 years using the Wechsler Adult Intelligence Scale-IV (WAIS-IV; IQ range, 40-160). Socioeconomic status (primary outcome) was assessed at age 38 years using the New Zealand Socioeconomic Index-2006 (NZSEI-06; range, 10 [lowest]-90 [highest]).
  
  
  
  Of 1037 original participants, 1007 were alive at age 38 years, of whom 565 (56%) had been lead tested at age 11 years (54% male; 93% white). Mean (SD) blood lead level at age 11 years was 10.99 (4.63) µg/dL. Among blood-tested participants included at age 38 years, mean WAIS-IV score was 101.16 (14.82) and mean NZSEI-06 score was 49.75 (17.12). After adjusting for maternal IQ, childhood IQ, and childhood socioeconomic status, each 5-µg/dL higher level of blood lead in childhood was associated with a 1.61-point lower score (95% CI, -2.48 to -0.74) in adult IQ, a 2.07-point lower score (95% CI, -3.14 to -1.01) in perceptual reasoning, and a 1.26-point lower score (95% CI, -2.38 to -0.14) in working memory. Associations of childhood blood lead level with deficits in verbal comprehension and processing speed were not statistically significant. After adjusting for confounders, each 5-µg/dL higher level of blood lead in childhood was associated with a 1.79-unit lower score (95% CI, -3.17 to -0.40) in socioeconomic status. An association between greater blood lead levels and a decline in IQ and socioeconomic status from childhood to adulthood was observed with 40% of the association with downward mobility mediated by cognitive decline from childhood.
  
  
  
  In this cohort born in New Zealand in 1972-1973, childhood lead exposure was associated with lower cognitive function and socioeconomic status at age 38 years and with declines in IQ and with downward social mobility. Childhood lead exposure may have long-term ramifications.
authors.affiliation: Department of Psychology and Neuroscience, Duke University, Durham, North Carolina.
authors.forename: Aaron
authors.initials: A
authors.lastname: Reuben
authors.affiliation: Department of Psychology and Neuroscience, Duke University, Durham, North Carolina2Center for Genomic and Computational Biology, Duke University, Durham, North Carolina3Department of Psychiatry and Behavioral Sciences, Duke University, Durham, North Carolina4Social, Genetic, and Developmental Psychiatry Centre, Institute of Psychiatry, Psychology, & Neuroscience, King's College, London, United Kingdom.
authors.forename: Avshalom
authors.initials: A
authors.lastname: Caspi
authors.affiliation: Social Science Research Institute, Duke University, Durham, North Carolina6Department of Medicine, Duke University School of Medicine, Durham, North Carolina.
authors.forename: Daniel W
authors.initials: DW
authors.lastname: Belsky
authors.affiliation: Sir John Walsh Research Institute, Faculty of Dentistry, University of Otago, Dunedin, New Zealand.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Broadbent
authors.affiliation: Department of Psychology and Neuroscience, Duke University, Durham, North Carolina.
authors.forename: Honalee
authors.initials: H
authors.lastname: Harrington
authors.affiliation: Department of Psychology and Neuroscience, Duke University, Durham, North Carolina.
authors.forename: Karen
authors.initials: K
authors.lastname: Sugden
authors.affiliation: Department of Psychology and Neuroscience, Duke University, Durham, North Carolina.
authors.forename: Renate M
authors.initials: RM
authors.lastname: Houts
authors.affiliation: Dunedin Multidisciplinary Health and Development Research Unit, Department of Psychology, University of Otago, Dunedin, New Zealand.
authors.forename: Sandhya
authors.initials: S
authors.lastname: Ramrakha
authors.affiliation: Dunedin Multidisciplinary Health and Development Research Unit, Department of Psychology, University of Otago, Dunedin, New Zealand.
authors.forename: Richie
authors.initials: R
authors.lastname: Poulton
authors.affiliation: Department of Psychology and Neuroscience, Duke University, Durham, North Carolina2Center for Genomic and Computational Biology, Duke University, Durham, North Carolina3Department of Psychiatry and Behavioral Sciences, Duke University, Durham, North Carolina4Social, Genetic, and Developmental Psychiatry Centre, Institute of Psychiatry, Psychology, & Neuroscience, King's College, London, United Kingdom.
authors.forename: Terrie E
authors.initials: TE
authors.lastname: Moffitt
mesh_terms: D000328:Adult; D000367:Age Factors; D002648:Child; D003071:Cognition; D003072:Cognition Disorders; D032882:Comprehension; D005260:Female; D006801:Humans; D007360:Intelligence; D007361:Intelligence Tests; D007854:Lead / Q000097:blood*; D008297:Male; D008570:Memory, Short-Term; D009520:New Zealand; D011446:Prospective Studies; D012737:Sex Factors; D012923:Social Class; D012937:Social Mobility
chemical_list: D007854:Lead