title: Cumulative social risk exposure, infant birth weight, and cognitive delay in infancy.
abstract: OBJECTIVE
  To determine the effect of exposure to multiple social risks on cognitive delay at 9 months of age; and whether obstetric factors mediate the relationship between cumulative social risk and cognitive delay.
  
  
  METHODS
  Data were from 8950 mother-child dyads participating in the first wave of the Early Childhood Longitudinal Study, Birth Cohort. Cognitive delay was defined as falling in the lowest 10% of mental scale scores from the Bayley Short Form-Research Edition. Five social risk factors were combined and categorized into a social risk index. Staged multivariable logistic regressions were used to investigate whether obstetric factors mediated the impact of social risk on the odds of cognitive delay.
  
  
  RESULTS
  Infants with cognitive delay were more likely to live with social risks than infants without cognitive delay. The percentage of infants with cognitive delay increased with the number of social risks. In adjusted analyses, exposure to multiple social risk factors was associated with higher odds of cognitive delay at 9 months of age (adjusted odds ratio 2.11; 95% confidence interval 1.18-3.78 for 4 or more risks vs no risks). Accounting for birth weight attenuated this relationship (P < .001).
  
  
  CONCLUSIONS
  This population-based study investigated the independent and cumulative effects of social risk factors on cognitive delay in infancy. Findings revealed a significant cumulative relationship between exposure to social risk and cognitive delay, which was partly mediated by birth weight. Programs that address the social context of US infants are needed to improve their developmental trajectories.
authors.affiliation: Division of General Academic Pediatrics, Center for Child and Adolescent Health Research and Policy, Harvard Medical School and the Massachusetts General Hospital for Children, Boston, Mass. Electronic address: ercheng@mgh.harvard.edu.
authors.forename: Erika R
authors.initials: ER
authors.lastname: Cheng
authors.affiliation: Department of Human Development and Family Studies, Waisman Center, University of Wisconsin, Madison, Wis.
authors.forename: Julie
authors.initials: J
authors.lastname: Poehlmann-Tynan
authors.affiliation: Department of Population Health Sciences, University of Wisconsin School of Medicine and Public Health, Madison, Wis.
authors.forename: John
authors.initials: J
authors.lastname: Mullahy
authors.affiliation: Truven Health Analytics, Bethesda, Md.
authors.forename: Whitney P
authors.initials: WP
authors.lastname: Witt
mesh_terms: D001724:Birth Weight; D002657:Child Development; D003072:Cognition Disorders / Q000209:etiology*; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008137:Longitudinal Studies; D008297:Male; D012307:Risk Factors; D012931:Social Environment; D012959:Socioeconomic Factors
keywords: birth weight; child development; infancy; life course; social environment