Althoff, R.

Bartels, M.

Boomsma, D.I.

English

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VU Research PortalAnesthesia and cognitive performance in children: No evidence for a causalrelationship. Are the conclusions justified by the data?Bartels, M.; Althoff, R.; Boomsma, D.I.published inTwin Research and Human Genetics2009DOI (link to publisher)10.1375/twin.12.6.613Link to publication in VU Research Portalcitation for published version (APA)Bartels, M., Althoff, R., & Boomsma, D. I. (2009). Anesthesia and cognitive performance in children: No evidencefor a causal relationship. Are the conclusions justified by the data? Twin Research and Human Genetics, 12(6),613-614. https://doi.org/10.1375/twin.12.6.613General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright ownersand it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.            • Users may download and print one copy of any publication from the public portal for the purpose of private study or research.            • You may not further distribute the material or use it for any profit-making activity or commercial gain            • You may freely distribute the URL identifying the publication in the public portal ?Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.E-mail address:vuresearchportal.ub@vu.nlDownload date: 03. Mar. 2023Anesthesia and Cognitive Performance in Children: No Evidence for a CausalRelationship. Are the ConclusionsJustified by the Data?Reply to Flick et al., 2009Meike Bartels,1 Robert Althoff,2 and Dorret I. Boomsma11 Department of Biological Psychology, VU University, Amsterdam, The Netherlands2 Departments of Psychiatry and Pediatrics, University of Vermont, Burlington, Vermont, United States of AmericaWe thank Flick and colleagues for their thoughts andtheir comments on our article. Although we agree thatthe published study has limitations, we think thatmany of the limitations might be overstated. Flick etal. assert that the conclusion that ‘there is no evidencefor a causal relationship between anesthesia adminis-tration and later learning-related outcomes’ should bequalified due to limitations of the study design and thedata. We disagree and welcome the opportunity toclarify how the design and the results of our studysupport this conclusion. First, we agree that we do not have systematicinformation on the duration of the anesthetics or thereason for surgery in the NTR sample. It is certainlythe case, from the work of Wilder et al. (2009), thatthat duration of exposure could have an effect. Wewould note, however, that duration of the anestheticsis positively correlated with the reason for surgery. Amore severe health problem in the child is oftenrelated to more intense surgery with longer use ofanesthetics. From the work that we presented, wewould suggest that a sicker child is also a more vulner-able child who, with or without anesthesia, may havea higher chance of developing learning disabilities.This is demonstrated by our finding that the non-exposed child of a discordant MZ twin pair scores aslow on educational attainment as the exposed child.Second, it is important to note that in our studythe between-subjects comparison (on all availabledata) showed the expected outcome, that is, theexposed children did worse than the non-exposed chil-dren even when using a simple measure of exposurethat did not take into account frequency.Next, we agree that anesthetic exposure per se isnot the only environmental factor that could influencelater learning problems. The impact of hospitalizationand other environmental influences could play a role.However, our study demonstrates that there are nodifferences between identical co-twins when one of thepair is exposed and the other is not and that theNON-exposed individual of the pair scores as low asthe exposed co-twin (both score lower than twins ofnonexposed pairs). Therefore, we suggest that thereare other (possibly genetic) factors that influencelearning disabilities. These factors are likely to becomorbid with anesthetic exposure. Response rates of the data collection of theNetherlands Twin Register have been published else-where. The NTR has an average response rate ofabout 80% for survey research with attrition beingrandom, with respect to childhood psychopathologyand dropout from the study (see Bartels et al., 2007).We apologize for the incompleteness of Table 2. Flickand colleagues were correct, the first two columns arefor males and the second are for females.Sample sizes vary by outcome variable due to thehistory of data collection. Questions on anestheticshave been collected since the start of the twin register(1986). Data collection for Educational Achievement(EA) data started in 2000. Moreover, twins have toreach age 12 before information on EA becomes avail-able. Data on Cognitive Problems (CP) were collectedfrom the Conners’ Teacher Rating Scale (CTRS-RS;Conners, 2001) and were also added to the data col-lection procedure in later years.Sample sizes for the between-individual analyses(Table 4 in the original paper) were indeed not pre-sented. We apologize for this oversight. The number ofchildren is added to Table 1 below between parenthe-ses (note these are not pairs but individuals). Thebetween-individual analyses were carried out usingdata from children concordant exposed (CON-E) andnon-exposed (CON-NE) pairs as well as children fromAddress for correspondence: Meike Bartels, Department of BiologicalPsychology, VU University, Amsterdam, The Netherlands. E-mail:m.bartels@psy.vu.nl613Twin Research and Human Genetics Volume 12  Number 6  pp. 613–614discordant pairs (DIS-E and DIS-NE). Please note thatsamples sizes change over time (under 3 years vs. everexposed before age 12).Flick et al. express concerns about statisticalpower. Across the analyses performed for boys andgirls, assuming power of .80, and an alpha of .05 weare able to detect small to medium effect sizes (withCohen’s d from .17–.40, depending on the analysis). Finally, we indicated in the paper that the measuresof EA and CP are not direct measures of learning dis-ability, but are indicators of cognitive performance.The correlation between Full-Scale WISC IQ and theEA measure is .63 (Bartels et al., 2002), which is iden-tical to the correlation between IQ and the EA measure(r = .62) used by Wilder et al. (2009). Thus, our results support the conclusion that thereis no direct causal effect of childhood anesthetic expo-sure on cognitive performance. We favor thehypothesis that there is an overall (genetic) vulnerabil-ity that underlies both the reason for anestheticexposure and cognitive problems. However, in orderto gain more insight into this important topic we arecurrently expanding our project to collect informationon the reason for and outcome of the surgeries andmore detailed information on anesthetic use withinour sample.ReferencesBartels, M., van Beijsterveldt, C. E. M., Stroet, T. M.,Hudziak, J. J., & Boomsma, D. I. (2007). Young-Netherlands Twin Register (Y-NTR); A longitudinalmultiple informant study of problem behavior. TwinResearch and Human Genetics, 10, 3–12.Bartels, M., Rietveld, M. J. H., Van Baal, G. C. M., &Boomsma, D. I. (2002). Heritability of educationalachievement in 12-year-olds and the overlap with cog-nitive abilities. Twin Research, 5, 544–554.Wilder, R. T., Flick, R. P., Sprung J, Katusic, S. K.,Barbaresi, W. J., Mickelson, C., Gleich, S. J., Schroeder,D. R., Weaver, A. L., & Warner, D. O. (2009). Earlyexposure to anesthesia and learning disabilities in apopulation-based birth cohort. Anesthesiology, 110,796–804.614 Twin Research and Human Genetics December 2009Meike Bartels, Robert Althoff, and Dorret I. BoomsmaTable 1Educational Achievement (EA) and Cognitive Problems (CP): Means for Subjects From Four Exposure Groups (Twins From Concordantor Discordant Pairs); Tests Were Done for Males and Females and for Exposure Under Age 3 and Exposure Ever Under Age 12EA exposure CON-NE DIS_NE DIS_E CON-EUnder 3 years: males* 539.48 (575) 536.76 (62) 536.4 (62) 537.5 (132)Ever exposed: males** 540.11 (396) 538.54 (99) 538.83 (98) 537.38 (301)Under 3 years: females*** 537.49 (876) 534.43 (49) 534.36 (50) 538.21 (98)Ever exposed: females 537.6 (591) 536.26 (129) 535.69 (127) 537.82 (276)CPUnder 3 years: males 2.69 (270) 2.98 (31) 2.75 (29) 2.63 (63)Ever exposed: males 2.92 (192) 2.9 (40) 2.73 (41) 2.57 (146)Under 3 years: females* 1.85 (411) 4.26 (28) 3.44 (31) 2.85 (55)Ever exposed: females* 1.74 (292) 2.86 (63) 2.67 (64) 2.38 (127)Note: * Concordant non-exposed twins score significantly higher on EA and lower on CP.** Concordant non-exposed twins score significantly higher than concordant exposed twins on EA.*** Concordant non-exposed and concordant exposed twins score significantly higher than discordant twins on EA.

Anesthesia and cognitive performance in children: No evidence for a causal relationship. Are the conclusions justified by the data?

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Anesthesia and cognitive performance in children: No evidence for a causal relationship. Are the conclusions justified by the data?

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