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Anesthesia and Babies' Brains: Lessons from the Lounge. Early Exposure to Anesthesia and Learning Disabilities in a Population-based Birth Cohort. By Wilder RT, Flick RP, Sprung J, Katusic SK, Barbaresi WJ, Mickelson C, Gleich SJ, Schroeder DR, Weaver AL, and Warner DO. A nesthesiology 2009; 110:796-804. Reprinted with permission. Anesthetic drugs administered to immature animals may cause neurohistopathologic changes and alterations in behavior. The authors studied association between anesthetic exposure before age 4 yr and the development of reading, written language, and math learning disabilities. This was a population-based, retrospective birth cohort study. The educational and medical records of all children born to mothers residing in five townships of Olmsted County, Minnesota, from 1976 to 1982 and who remained in the community at 5 yr of age were reviewed to identify children with learning disabilities. Cox proportional hazards regression was used to calculate hazard ratios for anesthetic exposure as a predictor of learning disabilities, adjusting for gestational age at birth, sex, and birth weight. Of the 5,357 children in this cohort, 593 received general anesthesia before age 4 yr. Compared with those not receiving anesthesia (n = 4,764), a single exposure to anesthesia (n = 449) was not associated with an increased risk of learning disabilities (hazard ratio, 1.0; 95% CI, 0.79 to 1.27). However, children receiving two anesthetics (n = 100) or three or more anesthetics (n = 44) were at increased risk for learning disabilities (hazard ratio, 1.59; 95% CI, 1.06 to 2.37; and hazard ratio, 2.60; 95% CI, 1.60 to 4.24, respectively). The risk for learning disabilities increased with longer cumulative duration of anesthesia exposure (expressed as a continuous variable; P = 0.016). Exposure to anesthesia was a significant risk factor for the later development of learning disabilities in children receiving multiple but not single anesthetics. These data cannot reveal whether anesthesia itself may contribute to learning disabilities or whether the need for anesthesia is a marker for other unidentified factors that contribute to learning disabilities.