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Breastfeeding And Verbal Ability Of 3 Year Olds In A Multicity Sample

Breastfeeding And Verbal Ability Of 3 Year Olds In A Multicity Sample






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    Breastfeeding And Verbal Ability Of 3 Year Olds In A Multicity Sample Breastfeeding And Verbal Ability Of 3 Year Olds In A Multicity Sample Document Transcript

    • Breastfeeding and Verbal Ability of 3-Year-Olds in a Multicity Sample Christina M. Gibson-Davis and Jeanne Brooks-Gunn Pediatrics 2006;118;e1444-e1451 DOI: 10.1542/peds.2006-0072 The online version of this article, along with updated information and services, is located on the World Wide Web at: http://www.pediatrics.org/cgi/content/full/118/5/e1444 PEDIATRICS is the official journal of the American Academy of Pediatrics. A monthly publication, it has been published continuously since 1948. PEDIATRICS is owned, published, and trademarked by the American Academy of Pediatrics, 141 Northwest Point Boulevard, Elk Grove Village, Illinois, 60007. Copyright © 2006 by the American Academy of Pediatrics. All rights reserved. Print ISSN: 0031-4005. Online ISSN: 1098-4275. Downloaded from www.pediatrics.org by on June 2, 2009
    • ARTICLE Breastfeeding and Verbal Ability of 3-Year-Olds in a Multicity Sample Christina M. Gibson-Davis, PhDa, Jeanne Brooks-Gunn, PhDb aTerry Sanford Institute of Public Policy, Duke University, Durham, North Carolina; bNational Center for Children and Families, Teacher’s College, and College of Physicians and Surgeons, Columbia University, New York, New York The authors have indicated they have no financial relationships relevant to this article to disclose. ABSTRACT OBJECTIVES. Our goal was to analyze the effect of maternal verbal ability and educa- tion on the association between breastfeeding and children’s cognitive function- www.pediatrics.org/cgi/doi/10.1542/ ing. First, we hypothesized that maternal verbal abilities account for a large portion peds.2006-0072 of the association between breastfeeding and child verbal abilities. Second, we doi:10.1542/peds.2006-0072 hypothesized that after adjusting for maternal verbal abilities, a positive effect of Key Words breastfeeding will be most evident among highly educated mothers, because these breastfeeding, cognition, maternal mothers may have more opportunity to engage in cognitively stimulating parent- educational status ing than do mothers with less education. Abbreviations PPVT—Peabody Picture Vocabulary Test PATIENTS AND METHODS. With data on 1645 American-born mothers participating in a FF—Fragile Families and Child Wellbeing Survey longitudinal birth cohort study, we used linear regression to determine the influ- HOME—Home Observation for ence of breastfeeding for at least 1 month on the Peabody Picture Vocabulary Measurement of the Environment LCPUFA—long-chain polyunsaturated Test-Third Edition scores of 3-year-old children. Models were adjusted for an fatty acids extensive set of demographic characteristics, including mother’s Peabody Picture Accepted for publication May 23, 2006 Vocabulary Test and the Home Observation for Measurement of the Environment Address correspondence to Christina M. score. Mothers were categorized into 1 of 3 educational-status groups: no high Gibson-Davis, PhD, Terry Sanford Institute of Public Policy, Duke University, PO Box 90245, school diploma, high school diploma, and some post–secondary education. Durham, NC 27708. E-mail: cgibson@duke.edu PEDIATRICS (ISSN Numbers: Print, 0031-4005; RESULTS. In unadjusted mean comparisons, breastfed children had Peabody Picture Online, 1098-4275). Copyright © 2006 by the Vocabulary Test scores that were 6.6 points higher than children who were not American Academy of Pediatrics breastfed. After adjusting for demographic characteristics and maternal verbal ability, the coefficient dropped to 1.72. Among mothers with education beyond high school, the children’s Peabody Picture Vocabulary Test scores in adjusted models were 2.2 points higher for breastfed children. Among mothers with a high school diploma or less, there were no significant differences in the children’s Peabody Picture Vocabulary Test scores by breastfeeding status. These results were consistent in white, black, and Hispanic children. CONCLUSIONS. Maternal Peabody Picture Vocabulary Test scores mediate much of the association between breastfeeding and child verbal abilities. The beneficial effects of breastfeeding on children’s cognition may emerge only when breastfeeding is done in conjunction with other positive parenting behaviors. The advantageous effects of breastfeeding do not seem to be solely attributable to the superior nutrient content of breast milk. e1444 GIBSON-DAVIS, BROOKS-GUNN Downloaded from www.pediatrics.org by on June 2, 2009
    • A LTHOUGH BREASTFEEDING IS widely regarded as beneficial for child and maternal health,1 its effect on children’s cognitive development remains an open METHODS Subjects The FF is a large birth cohort study of 3700 unmarried question. Mothers who breastfeed have more education, and 1200 married new parents. Couples were sampled higher incomes, and better mental and physical health from 75 hospitals in 20 large cities in 15 different states. than those who do not,2–5 and failure to adequately Mothers were interviewed in the hospital shortly after adjust for these differences can overestimate the effects giving birth, and fathers were interviewed either in the of breastfeeding. Maternal verbal ability seems particu- hospital or wherever they could be located. When the larly important, because it can account for the entire child was 1 and 3 years old, parents were surveyed by association between breastfeeding and child cognition.6,7 telephone. The FF surveyed parents on topics related to Nevertheless, many studies have found a positive effect child and family well-being, and additional details of the of breastfeeding on mental functioning,8–14 and a 20- study, including city and hospital selection, are pub- study meta-analysis found that breastfeeding increased lished elsewhere.22 cognition scores by 5 points for low birth weight infants At 3 years, an in-home assessment was conducted, and 3 points for normal birth weight infants.15 Two which included measures of both mother and child cogni- recent literature reviews16,17 also concluded that breast- tive ability and the quality of the child’s home environ- feeding was beneficial, particularly for low birth weight ment. Data used in this article come from the baseline children. survey, first- and third-year surveys, and the in-home The majority of previous studies have assumed that assessment. breastfeeding has a direct effect on child cognition; most At baseline, information was collected from 4898 commonly, this effect is ascribed to the superior nutri- mothers, of which 4231 (86%) participated in the year-3 ents found in breast milk.2,18,19 Yet, it is possible that telephone survey. Of the 4231 families, 3336 (79%) breastfeeding is beneficial because it occurs in the con- participated in some portion of the in-home assessment, text of other positive parenting practices. Breastfeeding but only 2182 (52%) participated in the child observa- mothers may respond more to the needs of their child, tion. Nonresponse on the child observation was a result spend more time in mother-child interaction, or engage of family relocation ( 85% of nonrespondents) or re- in more stimulating activities. These advantageous par- fusal (15% of nonrespondents). Of these 2182 observa- enting practices, together with breastfeeding, may pro- tions, an additional 221 were missing data on either the duce cognitive benefits. cognitive or the mother-child interaction outcomes, re- Advantageous parenting practices, particularly cogni- sulting in 1961 completed in-home assessments. Cases tively stimulating parenting, are strongly correlated with were also deleted if they were missing data on breast- maternal education,20,21 in part because better-educated feeding (n 62), the child had a physical disability (n mothers have more opportunities to provide stimulation 58), or the mother was not born in America (n 196), for their children. In this study we stratified our sample which resulted in a final sample size of 1645.* according to education level to analyze the association Informed consent was obtained from all participants. between breastfeeding and children’s verbal abilities. We The survey was approved by the internal review boards would expect that among better-educated mothers, of Princeton and Columbia Universities. those who breastfeed, relative to those who do not, will Subjects who completed the year-3 telephone survey have children with higher cognition scores. This associ- versus those who completed the in-home assessment ation may not exist among less-educated mothers, be- had few differences in demographic characteristics, with cause they may not be able to draw on the same re- the exception that they had lower household incomes sources as mothers with more education. and younger children. Mothers who participated in both We examined the effect of breastfeeding on a mea- the in-home assessment and the child observation, as sure of children’s verbal ability, the Peabody Picture compared with those who participated in the in-home Vocabulary Test-Third Edition (PPVT-III). Data come assessment without the child observation, were more from the Fragile Families and Child Wellbeing Survey likely to be black and have older children. (FF), a longitudinal birth cohort study drawn from 20 cities in 15 states. We first present estimates of breast- Measures and Procedure Maternal and child cognitive ability was measured at 3 feeding that have been adjusted for maternal PPVT-III years with the PPVT-III, a measure of receptive vocabu- scores, hypothesizing that maternal verbal ability medi- lary.23 The PPVT-III correlates well with standardized ates much of the effect of breastfeeding. Next, we test measures of intelligence such as the Wechsler Intelli- the hypothesis that breastfeeding is moderated by ma- ternal education by estimating separate models for 3 * Immigrant mothers were omitted because it was unclear if their educational status would be education groups: no high school diploma, high school adequately captured by the American-based measures. Including immigrant mothers does not diploma, and some post–secondary education. substantially change our results, nor does including children with a physical disability. PEDIATRICS Volume 118, Number 5, November 2006 e1445 Downloaded from www.pediatrics.org by on June 2, 2009
    • gence Scale-Third Edition.23 The PPVT-III was adminis- using the Composite International Diagnostic Interview tered in both English and Spanish by interviewers who Short Form,27,28 following the developer’s guidelines,29 to had received appropriate training. As has been done classify mothers who had a score of 3 as having a elsewhere,24 extreme PPVT-III scores were imputed; probable major depressive episode (according to Diagnos- scores below 55 were imputed to 55 for 104 children and tic and Statistical Manual of Mental Disorders, Fourth Edition 12 mothers. Because the average age at assessment was criteria). 36 months, 6% of children had PPVT-III scores of 55. The correlations between the 2 HOME scales and ma- Because the PPVT-III can only be administered to chil- ternal PPVT-III were low (r 0.31 in all cases). Correla- dren 3 years, this left-censoring reflects a basal effect. tions between the HOME measures and income, and be- Results do not change if scores below 55 are not im- tween HOME and maternal education, were all 0.20. The puted. The correlation between maternal PPVT-III and correlation between income and education was 0.43. child PPVT-III, education, and income was 0.42, 0.47, Most control variables were taken from the year-3 and 0.46, respectively. survey, because maternal PPVT-III and the HOME scores Breastfeeding behaviors, collected at year 1, were were only measured at that time. Race and ethnicity, based on mother’s report of how long she breastfed the parity, health behaviors during the pregnancy, and child. On the basis of the work of Jain et al,25 and child’s birth weight status and gender were gathered because mothers may change feeding methods within during the baseline interview. In other models not the first few weeks of life, mothers were classified as shown, we substituted year-3 variables for baseline vari- having breastfed if they did so for at least the first month. ables; using baseline measures of education, relationship Maternal educational status was classified into 3 status, age, and income did not substantively change our groups: those who did not complete high school, those results. who graduated from high school or obtained their gen- The association between breastfeeding and PPVT-III eral equivalency degree, and those who had some edu- scores was modeled by using hierarchical multivariate cation beyond high school.† Educational status was orig- regression. The first model estimated a bivariate associ- inally measured at baseline, but cases were coded to ation between breastfeeding and PPVT-III scores, and in reflect any additional education received. Home environment was measured through 2 inter- the second and subsequent models, additional blocks of viewer-rated scales of the Home Observation for Mea- covariates were added. Changes in the breastfeeding surement of the Environment (HOME) scale.26 The non- coefficient across models provided an indication of how punitive/hostility scale consisted of 5 items on which the breastfeeding was mediated by the other covariates. In interviewer rated the mother on the absence of antago- all models, to account for clustering within city, we used nistic or aggressive behaviors (eg, if the mother did not Huber-White standard errors that correct for potential shout or spank the child). The emotional-responsiveness nonindependence across observations. To address the scale consisted of 6 items that measured positive verbal problem of missing data in the control variables, we used maternal interactions (eg, if the mother spontaneously multiple imputation.30 In multiple imputation, every praised the child). For both scales, higher scores mean missing case is replaced by n simulated values, resulting better home environments. in n complete data sets. These data sets can then be Demographic variables included maternal and pater- analyzed by using standard regression methods, and the nal race/ethnicity and age, paternal education (mea- results are combined and adjusted for the multiple im- sured similarly to that of mothers), parity, and if the putation procedure. Rates of missing data were low, mother had a child subsequent to the child participating because only a few variables were missing in 4% of the in the FF. Marital status was measured through 4 dichot- cases. omous variables: married to the birth father (the refer- ence category), cohabiting with the birth father, no ro- mantic relationship, and married or cohabiting with a RESULTS new partner. Household income was the log of the Because the FF oversampled nonmarital births, the pop- mother’s household income averaged over the 3 rounds ulation is relatively disadvantaged in terms of cognitive of the survey. The child characteristics included if the ability, educational attainment, and income (Table 1). child was female, the child’s age (in months), and if the PPVT-III scores are normed to be 100 on national sam- child had a low birth weight. Maternal health variables ples, yet the FF PPVT-III scores were below national were pregnancy behaviors (smoked during pregnancy, norms for both children (86.8) and mothers (89.9). Ap- saw a doctor during first trimester), a self-report of proximately one quarter of mothers did not complete health status (if mother was is in good or excellent high school, and an additional third had no post–second- health), and depression. Depression was measured by ary education. Average yearly household income was $30 500. Only 40% of the mothers breastfed for at least † There were too few mothers who had a bachelor’s degree to constitute their own category. 1 month, a rate lower than that reported by the National e1446 GIBSON-DAVIS, BROOKS-GUNN Downloaded from www.pediatrics.org by on June 2, 2009
    • TABLE 1 Characteristics of the FF Survey (n 1645) Immunization Survey (62%).31 The sample was 60% Characteristic Average (SD) black and 20% Hispanic.‡ Breastfed at least 1 mo, % 40.3 Rates of breastfeeding and PPVT-III scores were PPVT-III score (child) 86.8 (15.1) higher for the mothers with more education. For breast- Cohabitating , % 25.3 feeding, 58% of the mothers with some post–secondary No romantic relationship, % 38.3 education breastfed for at least 1 month, as compared Cohabit with or married to new partner, % 10.5 with 27% of the mothers without a high school diploma Black, % 59.7 Hispanic, % 19.5 and 33% who had graduated from high school. Better- Father different race, % 13.7 educated mothers had higher PPVT-III scores (mean: Age, y 27.6 (5.9) 95.2) and children with higher PPVT-III scores (mean: Age (father), y 30.0 (7.0) 90.1) than either mothers with only a high school di- No high school, % 25.8 ploma (mean scores: 88.5 [mothers] and 84.4 [chil- High school only, % 31.0 No high school (father), % 27.2 dren]) or those who did not complete high school (mean High school (father), % 37.1 scores: 82.3 [mothers] and 83.1 [children]). Mothers Child was mother’s first, % 36.7 with some post–secondary education also had HOME Mother had subsequent child, % 28.4 scores that were one third to one half higher than moth- Household 3-y average income, $ 30 550 (29 798) ers with a high school diploma or less. Smoked during pregnancy, % 21.8 Saw doctor during first trimester, % 81.3 In bivariate associations (Table 2, model 1), the average Mother in good/excellent health, % 61.3 breastfed child had PPVT-III scores that were 6.2 points Probable case of depression, % 23.7 higher than a child who was not breastfed. This difference Characteristic, mean (SD) remained significant at the 5% level even after adjusting Female child, % 48.1 Child’s age, mo 35.5 (2.3) for demographics, health behaviors, and the HOME mea- Child had low birth weight, % 9.4 sures (models 2 and 3). However, the coefficient decreased HOME: emotional responsiveness score 5.50 (1.05) HOME: nonpunitive score 5.15 (1.34) PPVT-III score (mother) 89.9 (11.8) ‡ The Hispanic sample includes 28 mothers who classified themselves as another race or eth- nicity (eg, Asian or Pacific Islander). TABLE 2 Regression of Children’s PPVT-III Scores on Breastfeeding and Other Characteristics b (P) Model 1 Model 2 Model 3 Model 4 Breastfed at least 1 mo 6.22 (.000) 2.43 (.018) 2.56 (.009) 1.72 (.060) Cohabiting 3.75 (.000) 3.78 (.000) 3.03 (.002) No romantic relationship 2.89 (.013) 2.52 (.028) 2.10 (.072) Cohabit with or married to new partner 4.50 (.000) 4.29 (.000) 3.47 (.002) Black 7.91 (.000) 6.63 (.000) 4.13(.003) Hispanic 6.98 (.000) 6.90 (.000) 5.00 (.001) Father of different race 0.35 (.804) 0.31 (.815) 0.11 (.931) Age 0.25 (.014) 0.23 (.018) 0.26 (.017) Age (father) 0.25 (.002) 0.25 (.001) 0.24 (.003) No high school 1.69 (.171) 0.94 (.403) 1.38 (.272) High school only 2.19 (.011) 1.87 (.018) 0.83 (.255) No high school (father) 2.00 (.051) 1.94 (.052) 1.56 (.112) High school (father) 0.79 (.425) 0.89 (.353) 0.91 (.319) Child was mother’s first 1.75 (.073) 1.59 (.122) 1.52 (.101) Mother had subsequent child 2.63 (.012) 2.12 (.032) 2.08 (.047) Household 3-y average income (log) 1.60 (.005) 1.26 (.017) 0.33 (.430) Smoked during pregnancy 0.38 (.702) 0.42 (.644) 0.52 (.584) Saw doctor during first trimester 0.96 (.230) 0.55 (.436) 0.79 (.276) Mother in good/excellent health 0.39 (.544) 0.34 (.631) 0.18 (.777) Probable case of depression 0.38 (.580) 0.27 (.683) 0.66 (.353) Female child 1.77 (.006) 1.78 (.009) 1.76 (.008) Child’s age (months) 0.39 (.040) 0.42 (.008) 0.33 (.022) Child had low birth weight 3.32 (.008) 3.09 (.016) 2.67 (.028) HOME: emotional responsiveness 1.94 (.001) 1.69 (.000) HOME: nonpunitive/hostility scale 1.02 (.001) 0.95 (.002) PPVT-III score (mother) 0.33 (.000) Observations 1645 1645 1645 1645 R2 0.04 0.19 0.22 0.27 PEDIATRICS Volume 118, Number 5, November 2006 e1447 Downloaded from www.pediatrics.org by on June 2, 2009
    • to 1.72 once the mothers’ PPVT-III scores were added breastfed, their child’s PPVT-III score increased by 0.27 (model 4), and its P value increased to .060. points (P .05). Using the same progression of models, mothers were DISCUSSION next stratified by educational level (Table 3).§ The first 2 Previous research has indicated that children who are rows of the table indicate no significant bivariate associ- breastfed, in unadjusted comparisons with children who ation between breastfeeding and PPVT-III scores for are formula fed, score higher on measures of cognitive mothers with a high school diploma or less (model 1). functioning.3,9,10,32 The reasons for this difference, how- The coefficients were small (1.9 for mothers who did not ever, are unclear. It may be because breast milk contains complete high school, 2.1 for mothers who did), and the nutrients that promote optimum cognitive development; coefficients only decreased in subsequent models. alternatively, it could be a result of the advantageous The third row of Table 3 indicates that, among moth- characteristics of mothers who breastfeed. ers with some post–secondary education, children who One of those advantages is that mothers who breast- were breastfed scored 7.4 points higher (P .01) on the feed have higher verbal abilities.6,7 Given the high heri- PPVT-III than children who were not breastfed. Once tability in cognition between parent and child,33 models any covariates were included (model 2), the coefficient that do not control for maternal abilities risk finding a decreased to 3.7 points (P .01). The coefficient con- spurious correlation between breastfeeding and cogni- tinued to decline across models but remained significant; tive functioning. Our findings underscore this point, be- in the final model, breastfed children scored 2.2 points cause adjusting for maternal PPVT-III scores decreased higher on the PPVT-III (P .05). the size of the breastfeeding coefficient in the full sample In additional analyses not shown, mothers were di- by 48% and resulted in a coefficient that was no longer vided into education according to race and ethnicity statistically significant at the 5% level. The large effect of groups. Although the sample sizes were small, the pat- maternal PPVT-III is consistent with past research6,7 and tern of effects was similar. For non-Hispanic white, non- leads us to conclude that measures of maternal ability Hispanic black, and Hispanic children, it is only among must be included in studies on breastfeeding and child mothers with more education that breastfeeding was cognitive development. associated with an increase in PPVT-III scores. Another potential advantage associated with breast- Because of the importance of considering the dose- feeding is that it may be correlated with other positive response effects of breastfeeding, in other models not parenting practices. In this study, on the basis of past shown we classified breastfeeding according to duration: research that has found a strong positive correlation never breastfed (the reference category), breastfed for 1 between education and cognitively enriching parent- month, breastfed for 2 to 5 months, and breastfed for 6 ing,21,34 we had hypothesized that these parenting prac- months. In these models, there were no significant tices might be occurring among the better-educated breastfeeding effects among mothers without some post– mothers and had stratified our sample on the basis of secondary education. For better-educated mothers, the education group. We found that among mothers with coefficients for all 3 dichotomous breastfeeding mea- some post–secondary education, children who were sures were positive, but only the coefficient associated breastfed for at least 1 month had higher PPVT-III scores with breastfeeding for 6 months was significant at than those who were not. The gain was not large; once conventional levels (b 3.63; P .01). We also modeled all relevant maternal and child factors were taken into breastfeeding as a continuous variable. Breastfeeding account, the difference was 2 points. It is notable, how- had a significant and positive effect, but only for the ever, that there were no differences in PPVT-III scores, upper-education group; for every month this group even in unadjusted mean comparisons, for mothers with a high school diploma or less. A 2-point difference is 0.14 of an SD, a small effect § In additional models, we included an interaction term between breastfeeding and education. The according to Cohen’s rules35 for effect-size magnitude. term was not significant at conventional levels, but its positive direction was consistent with what we would expect. Furthermore, in these models, the associated breastfeeding coefficient decreased by However, the difference is similar to the gap in child 50%, indicating that some of its effect was moderated by the interaction term. PPVT-III between married and unmarried mothers (0.18 TABLE 3 Regression of Children’s PPVT-III on Breastfeeding According to Educational Status Breastfed at Least 1 mo b (P) Model 1 Model 2 Model 3 Model 4 No high school diploma (n 424) 1.94 (.061) 1.35 (.351) 1.46 (.293) .94 (.506) High school diploma (n 510) 2.06 (.286) .94 (.650) 1.34 (.501) 1.03 (.594) Post-secondary education (n 711) 7.39 (.000) 3.65 (.003) 3.53 (.002) 2.20 (.030) Model 1 is the bivariate association between breastfeeding and PPVT-III scores. Model 2 is model 1 plus marital status, age, race/ethnicity, parity, income, child characteristics, and health status. Model 3 is model 2 plus HOME scores. Model 4 is model 3 plus maternal PPVT-III. e1448 GIBSON-DAVIS, BROOKS-GUNN Downloaded from www.pediatrics.org by on June 2, 2009
    • of an SD). In addition, as explained by Rock and Sten- aware of any literature that documented a connection ner,36 small differences in a vocabulary-test score may between breastfeeding recall and education, and breast- not mean much for any one individual but can be con- feeding information was collected within 1 year of the sequential for groups of children (such as those entering child’s birth. Although the FF shows lower rates of into a kindergarten class). breastfeeding among high school dropouts than in other These results are consistent with the one study that surveys,4,37 this may reflect the minority nature of the has looked at breastfeeding by maternal educational sta- sample. White mothers, when stratified according to tus. Oddy et al11 found higher PPVT-R (revised edition) educational level, breastfed at rates commensurate with scores for breastfed infants, but only for mothers with a those from other large-scale surveys (results not college degree. The authors do not explain their educa- shown).38 Another source of bias could arise if inter- tion-breastfeeding interaction but instead attribute their viewers assigned higher PPVT-III scores to better-edu- significant findings to the beneficial properties of breast cated mothers. However, information on education sta- milk.11 tus was collected by telephone, whereas the PPVT-III Some limitations to our study should be noted. First, scores were gathered in person by a different inter- the FF cannot be generalized to the larger US popula- viewer. We also note that neither of these biases could tion. The FF oversampled births from unmarried couples account for differences found by breastfeeding status in cities across the United States, which resulted in a within the group of better-educated mothers. sample that is predominantly urban and low income. In the sample, mothers who completed the in-home Therefore, these results pertain to relatively disadvan- assessment were also more likely to be black. Because taged mothers who live in select cities, and the findings results were replicated in models estimated separately cannot be applied to the effect of maternal education for for white, black, and Hispanic mothers, we do not be- mothers with a bachelor’s degree or higher. Omitted lieve this selection unduly bias our findings. variable bias may also be a problem. Although models This work occurs in the context of other studies that controlled for a broad set of characteristics, there may be have attributed the beneficial effects of breastfeeding to other relevant parenting behaviors and/or environmen- the presence of long-chain polyunsaturated fatty acids tal factors that were not included. (LCPUFAs) in breast milk.2,11,12,14,39,40 LCPUFAs are nec- Another disadvantage of the FF is that it does not essary for retinal and neural development,3,18,41,42 and contain measures of exclusive breastfeeding. It is unclear animal studies indicate that severe LCPUFA deprivation if mothers used formula, when they began to do so, and negatively affects cognitive and behavioral perfor- how much they used. This limitation has important im- mance.43 Evidence showing a causal role between plications, because well-educated mothers are more LCPUFAs and enhanced human neural functioning, likely to exclusively breastfeed.4 Therefore, it is possible however, is inconclusive.19,41,43,44 Although these findings that the lack of observed effect among lower-educated do not relate directly to possible associations between women is because some breastfeeding mothers are ac- LCPUFAs and cognition, they may indicate that LCPUFAs tually supplementing with formula, and both groups by themselves are insufficient to create cognitive gains. are being conflated in the comparison between mothers who do and do not breastfeed. The effects among better- CONCLUSIONS educated mothers could also be explained, because that The finding of a positive effect of breastfeeding but only might represent a more accurate comparison between for better-educated mothers could be because of the infants who are breastfed and those who are not breast- larger parental context in which breastfeeding occurs. fed. Unfortunately, data limitations preclude identifying Research on breastfeeding exclusivity has found that what parental factors, beyond the 2 HOME measures, the majority of mothers of all educational levels who are important. It is unclear, therefore, if breastfeeding initiated breastfeeding do so exclusively for at least the stimulates better parenting behaviors, if breastfeeding first month of life.4 On the basis of this evidence, we only shows positive effects when done in conjunction infer that most mothers who breastfeed for the first with these behaviors, or some combination of the two. month are doing so exclusively. We are less sanguine Nevertheless, these results indicate that those perform- about the results that use different durations of breast- ing research into breastfeeding and cognition should feeding, because it is likely that some mothers classified consider the parental context, and training and support as breastfeeding are supplementing with formula. Nev- in parenting skills are important regardless of whether ertheless, these results are consistent with our earlier the mother breastfeeds or bottle feeds. findings. There are other sources of potential bias. Because the ACKNOWLEDGMENTS breastfeeding data are retrospective, the results may be The Fragile Families and Child Wellbeing Study is funded biased if better-educated mothers can report their by National Institute of Child Health and Human Develop- breastfeeding behaviors more accurately. We are un- ment grants R01HD369I6, R01HD41141, HD40933-04, PEDIATRICS Volume 118, Number 5, November 2006 e1449 Downloaded from www.pediatrics.org by on June 2, 2009
    • and HD40421-03, the California Healthcare Foundation, breastfeeding on cognitive development of infants born small the Center for Research on Religion and Urban Civil Soci- for gestational age. Acta Paediatr. 2002;913:267–275 10. Quinn PJ, O’Callaghan M, Williams GM, Najman JM, ety at the University of Pennsylvania, the Commonwealth Andersen MJ, Bor W. The effect of breastfeeding on child Fund, the Ford Foundation, the Foundation for Child De- development at 5 years: a cohort study. J Paediatr Child Health. velopment, the Fund for New Jersey, the William T. Grant 2001;37:465– 469 Foundation, the Healthcare Foundation of New Jersey, the 11. Oddy WH, Kendall GE, Blair E, et al. Breast feeding and cog- William and Flora Hewlett Foundation, the Hogg Founda- nitive development in childhood: a prospective birth cohort study. Paediatr Perinat Epidemiol. 2003;17:81–90 tion, the Christina A. Johnson Endeavor Foundation, the 12. Angelsen NK, Vik T, Jacobsen G, Bakketeig LS. Breast feeding Kronkosky Charitable Foundation, the Leon Lowenstein and cognitive development at age 1 and 5 years. Arch Dis Child. Foundation, the John D. and Catherine T. MacArthur 2001;85:183–188 Foundation, the A. L. Mailman Family Foundation, the 13. Horwood LJ, Darlow BA, Mogridge N. Breast milk feeding and Charles S. Mott Foundation, the National Science Founda- cognitive ability at 7– 8 years. Arch Dis Child Fetal Neonatal Ed. tion, the David and Lucile Packard Foundation, the Public 2001;84:F23–F27 14. Lucas A, Morley R, Cole TJ, Lister G, Payne-Leeson C. Breast Policy Institute of California, the Robert Wood Johnson milk and subsequent intelligence quotient in children born Foundation, the St David’s Hospital Foundation, St Vincent preterm. Lancet. 1992;339:261–264 Hospital and Health Services, and the US Department of 15. Anderson JW, Johnstone BM, Remley DT. Breast-feeding and Health and Human Services. Dr Gibson-Davis thanks the cognitive development: a meta-analysis. 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    • Breastfeeding and Verbal Ability of 3-Year-Olds in a Multicity Sample Christina M. Gibson-Davis and Jeanne Brooks-Gunn Pediatrics 2006;118;e1444-e1451 DOI: 10.1542/peds.2006-0072 Updated Information including high-resolution figures, can be found at: & Services http://www.pediatrics.org/cgi/content/full/118/5/e1444 References This article cites 33 articles, 9 of which you can access for free at: http://www.pediatrics.org/cgi/content/full/118/5/e1444#BIBL Citations This article has been cited by 1 HighWire-hosted articles: http://www.pediatrics.org/cgi/content/full/118/5/e1444#otherarti cles Subspecialty Collections This article, along with others on similar topics, appears in the following collection(s): Nutrition & Metabolism http://www.pediatrics.org/cgi/collection/nutrition_and_metabolis m Permissions & Licensing Information about reproducing this article in parts (figures, tables) or in its entirety can be found online at: http://www.pediatrics.org/misc/Permissions.shtml Reprints Information about ordering reprints can be found online: http://www.pediatrics.org/misc/reprints.shtml Downloaded from www.pediatrics.org by on June 2, 2009