Early-Life Lead Exposure and Visual Acuity in Infants

Abstract

Background- Lead (Pb) exposure during childhood has been associated with numerous deficits in neurobehavioral, motor, and cognitive functions. The effects of Pb on sensory function are less well-studied, and only in animals. The rapid increase in visual acuity (VA) in infancy reflects increasing myelination to a large degree and overall maturation of the central nervous system. VA might thus be sensitive to effects of Pb. Aim- To investigate the effect of early life Pb exposure on infant grating VA. Methods- Pb was measured using AAS in umbilical cord blood and infant blood at 9 months and 18 months in a cohort of healthy, full-term infants born in rural Fuyang County near Hangzhou, China between 2008-2011. VA was measured in infants using Teller Acuity Cards at 6 weeks (N=354), 9 months (N=330), and 18 months (N=285) and assigned as the narrowest grid the infant fixated on. Multivariate linear regression was used to evaluate relationships between cord, 9 month, or 18 month Pb and VA at 6 weeks, 9 months, or 18 months. Results- Means for Pb were 3.1, 4.4, and 3.6 µg/dL, for cord, 9 months, and 18 months, respectively. 9-month VA was lower in infants with higher concurrent blood Pb at 9 months. In adjusted models, VA decreased by 0.12 units (95%CI: 0.02-0.22) per every 1 µg/dL increase in concurrent blood Pb (p=0.02). Further analysis using quartiles revealed a highly linear association (ß= -1.41, -1.03, -0.26, for the upper three quartiles vs. the lowest one, respectively; p-trend=0.0001). No significant associations were observed at the other time points. Conclusions- VA at 9 months was lower in infants with higher concurrent blood Pb. The observed inverse association between VA and blood Pb at 9 months suggests that early life exposure to Pb may adversely affect myelination and visual system development.