To the Editor:—
Given the potential ramifications of findings linking early anesthesia exposure to the later development of learning disabilities (LDs), we expectantly read the article by Wilder et al. 1titled “Early Exposure to Anesthesia and Learning Disabilities in a Population-based Birth Cohort.” This topic was not only of interest to the medical community, but also garnered significant attention from the lay media. However, despite the authors' interesting and thought-provoking conclusion that multiple anesthetic exposure in children before age 4 yr increased the risk of developing a subsequent LD, we caution against the overinterpretation of associations without investigation of potentially important medical, psychological, and psychosocial confounders.
For example, Wilder et al. used a less stringent, study-defined definition of LD, as opposed to that of the Diagnostic and Statistical Manual of Mental Disorders published by the American Psychiatric Association.1,2Included in the Diagnostic and Statistical Manual of Mental Disorders criteria is the following caveat: “If a sensory deficit is present, the learning difficulties must be in excess of those usually associated with the deficit.”2This Diagnostic and Statistical Manual of Mental Disorders provision to the diagnosis of an LD is particularly relevant to the authors' study, which included multiple children with known medical diagnoses associated with sensory deficits. Similarly, many of the patients in the study cohort who received multiple anesthetics and were subsequently diagnosed with a LD also had medical diagnoses that may have contributed to their low achievement and led to their inclusion in a broadly study-defined LD group. For example, 2 children who were subsequently diagnosed with an LD had Sturge–Weber syndrome, and another child had cerebral palsy. It thus seems reasonable to question whether the LDs in these children are really “in excess” of those usually associated with these medical conditions.
Furthermore, the authors report an incidence of LDs in the Olmsted County, Minnesota general population as 20.0% for children not receiving an anesthetic, and 20.4% and 35.1% in children receiving one or multiple anesthetics, respectively. This is significant because the inclusion criteria used for the diagnosis of an LD in the authors' study resulted in an incidence more than double that reported in the 2007 Summary Health Statistics for U.S. Children: National Health Interview Survey, which reported an LD incidence of 8% in children aged 3–17 yr.3In addition, the LD prevalence reported in the Diagnostic and Statistical Manual of Mental Disorders ranges from 2% to 10%, depending on the diagnostic criteria used.2Finally, in examining the authors' previous publications based on the same population cohort, the “low achievement criteria” diagnosed reading disability (11.8% vs. 5.3%) and math disability (13.8% vs. 5.9%) at more than double the rate of the criteria used by the Minnesota Department of Education, and significantly higher than the other diagnostic criteria used in the current study.4,5Indeed, it would be interesting to view the results obtained when each diagnostic criterion used in the current study was displayed individually (similar to the authors' previous studies of this same population).
The study of anesthetic effects on childhood neurodevelopment is both timely and clinically relevant, and the authors are to be commended for attempting the difficult task of translating animal research findings into humans. However, more rigorous clinical evaluations of the effects of anesthetics on the developing human brain, including controlling for potential confounders (e.g. , medical diagnoses, type of surgery, prenatal history) using a multivariate model and propensity scoring are needed before drawing a link between anesthetic use in children and the subsequent development of LDs. As suggested by the title, the lay media is all too quick to jump on such an extremely controversial and sensitive topic, while at the same time preying on parents' worst fears.
†Baylor College of Medicine and Texas Heart Institute, St. Luke's Episcopal Hospital, Houston, Texas. ccollard@bcm.tmc.edu
