Breastfeeding and the child cognitive outcomes: a propensity score matching approach

Best for Whom? Heterogeneous Treatment Effects of Breastfeeding on Child Development

The slogan "Breast is Best" has been popularized by medical organizations and parenting networks to extoll the benefits of breastfeeding, yet the causal effects are widely debated. Our study contributes to the debate by examining whether breastfeeding has differential effects based on the propensity to breastfeed, which is also known as causal effect heterogeneity. Prior studies attempt to isolate the causal effect of breastfeeding by netting out confounding characteristics, but we argue that the effects of breastmilk are unlikely to operate in a vacuum. The social forces that promote or constrain breastfeeding among different populations in American society can also shape its effects. Using rich intergenerational panel data from the NLSY79 Child and Young Adult cohort (n = 7902), we evaluate heterogeneous treatment effects in the relationship between breastfeeding and child development from ages 4 to 14 using stratification-multilevel propensity score models. We find that breastfeeding is associated with small benefits for behavioral development, math scores, and academic ability among those with the highest propensities to breastfeed. By contrast, its small benefits for reading comprehension and vocabulary are concentrated among children with the lowest propensities to breastfeed. Our findings suggest that the social process of selection into breastfeeding cannot be fully disentangled from its estimated effects. The social context not only shapes who breastfeeds in American society, but also who benefits most.

Unraveling the effects of maternal breastfeeding duration and exclusive breast milk on children's cognitive abilities in early childhood

Background

This study investigated the putative associations between mothers' use of exclusive breast milk and the duration of breastfeeding with child cognitive development.

Methods

This study is based on 2,210 Canadian families with children assessed longitudinally from age 4 to 7 years on their memory-span and math skills. These cognitive abilities were measured with standardized tasks. Breastfeeding practices were collected via maternal reports. We applied propensity scores to control the social selection bias for breastfeeding.

Results

Results adjusted for propensity scores and sample weight revealed no significant differences between non-breastfed children with those being non-exclusively breastfed for 5 months or less, and with children being exclusively breastfed for 9.2 months on average, on their early math skills and memory-span. We found that children who were non-exclusively breastfed for 6.8 months on average had a slightly higher levels of memory-span at age 4 than children who were never breastfed, and this small but significant difference lasted up to age 7.

Conclusion

Our findings suggest no significant differences between children being exclusively breastfed and those fed with formula on their early math skills and memory-span. The encouragement of breastfeeding to promote child cognitive school readiness may, in some case (non-exclusive breastfeeding for more than 5 months), show a small but long-lasting advantage in early memory-span.

Breastfeeding Duration Is Associated With Domain-Specific Improvements in Cognitive Performance in 9-10-Year-Old Children

Significant immunological, physical and neurological benefits of breastfeeding in infancy are well-established, but to what extent these gains persist into later childhood remain uncertain. This study examines the association between breastfeeding duration and subsequent domain-specific cognitive performance in a diverse sample of 9-10-year-olds enrolled in the Adolescent Brain Cognitive Development (ABCD) Study®. The analyses included 9,116 children that attended baseline with their biological mother and had complete neurocognitive and breastfeeding data. Principal component analysis was conducted on data from an extensive battery of neurocognitive tests using varimax-rotation to extract a three-component model encompassing General Ability, Executive Functioning, and Memory. Propensity score weighting using generalized boosted modeling was applied to balance the distribution of observed covariates for children breastfed for 0, 1-6, 7-12, and more than 12 months. Propensity score-adjusted linear regression models revealed significant association between breastfeeding duration and performance on neurocognitive tests representing General Ability, but no evidence of a strong association with Executive Function or Memory. Benefits on General Ability ranged from a 0.109 (1-6 months) to 0.301 (>12 months) standardized beta coefficient difference compared to those not breastfed. Results indicate clear cognitive benefits of breastfeeding but that these do not generalize to all measured domains, with implications for public health policy as it pertains to nutrition during infancy.

Association of infant and young child feeding practices with cognitive development at 10–12 years: a birth cohort in rural Western China

We aimed to comprehensively examine the association of breast-feeding, types and initial timing of complementary foods with adolescent cognitive development in low- and middle-income countries. We conducted a prospective cohort study of 745 adolescents aged 10–12 years who were born to women who participated in a randomised trial of prenatal micronutrient supplementation in rural Western China. An infant feeding index was constructed based on the current WHO recommendations. Full-scale intelligence quotient (FSIQ) was assessed and derived by the fourth edition of the Wechsler Intelligence Scale for Children. The duration of exclusive or any breast-feeding was not significantly associated with adolescent cognitive development. Participants who regularly consumed Fe-rich or Fe-fortified foods during 6–23 months of age had higher FSIQ than those who did not (adjusted mean differences 4·25; 95 % CI 1·99, 6·51). For cows’/goats’ milk and high protein-based food, the highest FSIQ was found in participants who initially consumed at 10–12 and 7–9 months, respectively. A strong dose–response relationship of the composite infant feeding index was also identified, with participants in the highest tertile of overall feeding quality having 3·03 (95 % CI 1·37, 4·70) points higher FSIQ than those in the lowest tertile. These findings suggest that appropriate infant feeding practices (breast-feeding plus timely introduction of appropriate complementary foods) were associated with significantly improved early adolescent cognitive development scores in rural China. In addition, improvement in Fe-rich or Fe-fortified foods complementary feeding may produce better adolescent cognitive development outcomes.

Is breast feeding associated with offspring IQ at age 5? Findings from prospective cohort: Lifestyle During Pregnancy Study

OBJECTIVES

Breast feeding is associated with health benefits for both mother and child, but many studies focusing on neurodevelopment have lacked information on important confounders and few randomised trials exist. Our objective was to examine the influence of breast feeding on child IQ at 5 years of age while taking maternal IQ and other relevant factors into account.

DESIGN

Prospective observational study.

SETTING

Population-based birth cohort in Denmark.

PARTICIPANTS

We used data from The Lifestyle During Pregnancy Study 1782 mother-child pairs sampled from the Danish National Birth Cohort (n=101 042).

OUTCOME MEASURES

Child IQ was assessed at age 5 years by the Wechsler Primary and Preschool Scales of Intelligence-Revised. On the same occasion maternal intelligence was assessed by Wechsler Adult Intelligence Scale and Raven's Standard Progressive Matrices. Exposure data on duration of breast feeding (n=1385) were extracted from telephone interviews conducted when the child was 6 and 18 months, and analyses were weighted by relevant sampling fractions.

RESULTS

In multivariable linear regression analyses adjusted for potential confounders breast feeding was associated with child IQ at 5 years (categorical χ2 test for overall association p=0.03). Compared with children who were breast fed ≤1 month, children breast fed for 2-3, 4-6, 7-9 and 10 or more months had 3.06 (95% CI 0.39 to 5.72), 2.03 (95% CI -0.38 to 4.44), 3.53 (95% CI 1.18 to 5.87) and 3.28 (95% CI 0.88 to 5.67) points higher IQ after adjustment for core confounders, respectively. There was no dose-response relation and further analyses indicated that the main difference in IQ was between breast feeding ≤1 month versus >1 month.

CONCLUSIONS

Breastfeeding duration of 1 month or shorter compared with longer periods was associated with approximately three points lower IQ, but there was no evidence of a dose-response relation in this prospective birth cohort, where we were able to adjust for some of the most critical confounders, including maternal intelligence.

Using Propensity Score Matching to Address Clinical Questions: The Impact of Remote Microphone Systems on Language Outcomes in Children Who Are Hard of Hearing

Purpose Children who are hard of hearing (CHH) have restricted access to acoustic and linguistic information. Increased audibility provided by hearing aids influences language outcomes, but the benefits of hearing aids are often limited by acoustic factors and distance. Remote microphone (RM) systems further increase auditory access by reducing the negative consequences of these factors. The purpose of this article was to identify factors that influence likelihood of RM system receipt and to investigate the effects of RM systems in home settings on later language outcomes. We used propensity score matching to compare language outcomes between children with and without access to personal RM systems in home settings. This article provides a description of how and why to perform propensity score-matching analyses with clinical populations. Method Participants were 132 CHH. Through parent report, we identified children who received RM systems for home use by 4 years of age. Logistic regression was used to determine factors that predict likelihood of RM system receipt in home settings. Propensity score matching was conducted on a subgroup of 104 participants. Performance on language measures at age 5 years was compared across propensity-matched children who did and did not receive RMs for personal use. Results Likelihood of RM receipt was associated with degree of hearing loss, maternal education, and location (recruitment site). Comparisons between matched pairs of children with and without RM systems in early childhood indicated significantly better discourse skills for children whose families owned RM systems, but no significant differences for vocabulary or morphosyntax. Conclusion Results provide preliminary evidence that the provision of personal RM systems for preschool-age CHH enhances higher-level language skills. The propensity score-matching technique enabled us to use an observational, longitudinal data set to examine a question of clinical interest.

The best of intentions: Prenatal breastfeeding intentions and infant health

Health organizations recommend that mothers exclusively breastfeed infants for the first six months of life. The current study contributes to a growing body of research that examines whether the purported benefits of breastfeeding are causal. We systematically evaluated the role of an expectant mother's prenatal breastfeeding intentions, which reflect not only demographic characteristics, but also knowledge, attitudes, and social norms about infant feeding, and therefore serve as a proxy for positive maternal selection into breastfeeding. We used the Infant Feeding Practices Study (IFPS) II (n = 1008) to examine a heretofore overlooked group of mothers-those who intended to breastfeed but did not actually breastfeed. Results suggest that mothers who intended to breastfeed had infants with fewer ear infections and respiratory syncytial viruses, and used fewer antibiotics in the first year of life compared to infants whose mothers did not intend to breastfeed, irrespective of whether they actually breastfed. Because breastfeeding intention is a confounding characteristic that proxies for positive maternal selection and does not represent a causal mechanism for infant health, we further examined how mothers who intended to breastfeed differed from mothers who did not intend to breastfeed. Results suggest that mothers who intended to breastfeed had more knowledge about potential food contaminants and consulted more sources of information about nutrition and diet than mothers who did not intend to breastfeed. Taken together, our results underscore the need for new policy interventions aimed at improving infant health.

Maternal Mental Health after Custody Loss and Death of a Child: A Retrospective Cohort Study Using Linkable Administrative Data

OBJECTIVE

The objective was to compare mental illness diagnoses and treatment use among mothers who lost custody of their child through involvement with child protection services and those seen in mothers dealing with the death of a child.

METHODS

We studied mental health outcomes of a cohort of women whose first child was born in Manitoba, Canada between 1 April 1997 and 31 March 2015. Of these women, 5,792 had a child taken into care, and 1,143 mothers experienced the death of a child (<18 y old) before 31 March 2015. Adjusted relative rates (ARR) of 3 mental health diagnoses and 3 mental health treatment use outcomes between these 2 groups were examined.

RESULTS

Mothers with a child taken into care had significantly greater ARR of depression (ARR = 1.90; 95% CI, 1.82 to 1.98), anxiety (ARR = 2.51; 95% CI, 2.40 to 2.63), substance use (ARR = 8.54; 95% CI, 7.49 to 9.74), physician visits for mental illness (ARR = 3.01; 95% CI, 2.91 to 3.12), and psychotropic medication use (ARR = 4.95; 95% CI, 4.85 to 5.06) in the years after custody loss compared with mothers who experienced the death of a child.

CONCLUSION

Losing custody of a child to child protection services is associated with significantly worse maternal mental health than experiencing the death of a child. Greater acknowledgement and supportive services should be provided to mothers experiencing the loss of a child through the involvement of child protection services.

Effects of recruiting midwives into family physician program on the percentage of low birth weight (LBW) infants in rural areas of Kurdistan

Background: LBW is an important factor that can affect infant mortality and represents an index of economic and social development. It is expected that an increase in the density of midwives attending family physician programs will lead to a decrease in LBW in health centers. This study aimed to compare the percentage of LBW infants before and after the implementation of the family physician program in health centers with and without an increase in midwives density.

Methods: This cross-sectional study compared the percentage of LBW infants before and after the implementation of family physician programs in rural health centers with and without changes in midwives density in Kurdistan. In this study, we included 668 mothers of 2-month-old children and administered structured interviews in 2005 and 2013. Data were analyzed using the difference-indifferences and the Matchit statistical models.

Results: The Matchit model showed a significant average percentage increase 0.08 (0.006–0.17) in LBW infants born between 2005 and 2013 in health centers where the density of midwives increased compared with those where it remained unchanged. The difference-in-differences model showed that the odds ratio of LBW infants is increased by more than twice among participants who had a history of caesarean section.

Conclusion: The results of this study showed that an increase in the density of midwives in a family physician program did not have an impact on reducing the percentage of LBW infants born between 2005 and 2013, in health centers where the density of midwives augmented compared to those where it remained unaltered; it indicated that the increase in the density of midwives alone was not efficient. On the other hand, the results of our study show an increase in the risk of infants born at a LBW due to caesarean section. It is recommended that obstetricians and gynecologists must strictly control pregnancies and avoid unnecessary termination of pregnancy

Breastfeeding, Cognitive and Noncognitive Development in Early Childhood: A Population Study

BACKGROUND AND OBJECTIVES

There is mixed evidence from correlational studies that breastfeeding impacts children's development. Propensity score matching with large samples can be an effective tool to remove potential bias from observed confounders in correlational studies. The aim of this study was to investigate the impact of breastfeeding on children's cognitive and noncognitive development at 3 and 5 years of age.

METHODS

Participants included ∼8000 families from the Growing Up in Ireland longitudinal infant cohort, who were identified from the Child Benefit Register and randomly selected to participate. Parent and teacher reports and standardized assessments were used to collect information on children's problem behaviors, expressive vocabulary, and cognitive abilities at age 3 and 5 years. Breastfeeding information was collected via maternal report. Propensity score matching was used to compare the average treatment effects on those who were breastfed.

RESULTS

Before matching, breastfeeding was associated with better development on almost every outcome. After matching and adjustment for multiple testing, only 1 of the 13 outcomes remained statistically significant: children's hyperactivity (difference score, -0.84; 95% confidence interval, -1.33 to -0.35) at age 3 years for children who were breastfed for at least 6 months. No statistically significant differences were observed postmatching on any outcome at age 5 years.

CONCLUSIONS

Although 1 positive benefit of breastfeeding was found by using propensity score matching, the effect size was modest in practical terms. No support was found for statistically significant gains at age 5 years, suggesting that the earlier observed benefit from breastfeeding may not be maintained once children enter school.

Factors Associated with Breastfeeding Initiation: A Comparison between France and French-Speaking Canada

Background

Breastfeeding is associated with multiple domains of health for both mothers and children. Nevertheless, breastfeeding initiation is low within certain developed countries. Furthermore, comparative studies of initiation rates using harmonised data across multiple regions is scarce.

Objective

The aim of the present study was to investigate and compare individual-level determinants of breastfeeding initiation using two French-speaking cohorts.

Methods

Participants included ~ 3,900 mothers enrolled in two cohort studies in Canada and France. Interviews, questionnaires, and medical records were utilised to collect information on maternal, family, and medical factors associated with breastfeeding initiation.

Results

Rates of breastfeeding initiation were similar across cohorts, slightly above 70%. Women in both Canada and France who had higher levels of maternal education, were born outside of their respective countries and who did not smoke during pregnancy were more likely to initiate breastfeeding with the cohort infant. Notably, cohort effects of maternal education at the university level were found, whereby having ‘some university’ was not statistically significant for mothers in France. Further, younger mothers in Canada, who delivered by caesarean section and who had previous children, had reduced odds of breastfeeding initiation. These results were not found for mothers in France.

Conclusions and Implications for Practice

While some similar determinants were observed, programming efforts to increase breastfeeding initiation should be tailored to the characteristics of specific geographical regions which may be heavily impacted by the social, cultural and political climate of the region, in addition to individual and family level factors.

Teenage pregnancy: the impact of maternal adolescent childbearing and older sister's teenage pregnancy on a younger sister

BACKGROUND

Risk factors for teenage pregnancy are linked to many factors, including a family history of teenage pregnancy. This research examines whether a mother's teenage childbearing or an older sister's teenage pregnancy more strongly predicts teenage pregnancy.

METHODS

This study used linkable administrative databases housed at the Manitoba Centre for Health Policy (MCHP). The original cohort consisted of 17,115 women born in Manitoba between April 1, 1979 and March 31, 1994, who stayed in the province until at least their 20(th) birthday, had at least one older sister, and had no missing values on key variables. Propensity score matching (1:2) was used to create balanced cohorts for two conditional logistic regression models; one examining the impact of an older sister's teenage pregnancy and the other analyzing the effect of the mother's teenage childbearing.

RESULTS

The adjusted odds of becoming pregnant between ages 14 and 19 for teens with at least one older sister having a teenage pregnancy were 3.38 (99 % CI 2.77-4.13) times higher than for women whose older sister(s) did not have a teenage pregnancy. Teenage daughters of mothers who had their first child before age 20 had 1.57 (99 % CI 1.30-1.89) times higher odds of pregnancy than those whose mothers had their first child after age 19. Educational achievement was adjusted for in a sub-population examining the odds of pregnancy between ages 16 and 19. After this adjustment, the odds of teenage pregnancy for teens with at least one older sister who had a teenage pregnancy were reduced to 2.48 (99 % CI 2.01-3.06) and the odds of pregnancy for teen daughters of teenage mothers were reduced to 1.39 (99 % CI 1.15-1.68).

CONCLUSION

Although both were significant, the relationship between an older sister's teenage pregnancy and a younger sister's teenage pregnancy is much stronger than that between a mother's teenage childbearing and a younger daughter's teenage pregnancy. This study contributes to understanding of the broader topic "who is influential about what" within the family.

Effects of Recruiting Midwives into a Family Physician Program on Women's Awareness and Preference for Mode of Delivery and Caesarean Section Rates in Rural Areas of Kurdistan

BACKGROUND

The accepted rate rate of caesarean section is 15%. It is expected that an increase in the density of midwives in the family physician program lead to a decrease in this indicator. This study aimed to compare the rates of caesarean section and women's awareness and preference for mode of delivery before and after the implementation of the family physician program in health centres with and without an increase in midwives density.

METHODS

In this cross-sectional study, using multistage cluster sampling method a total of 668 mothers with two-month-old children were selected from among all mothers with two-month-old children who were living in rural areas of Kurdistan province. Using the difference-in-differences model and Matchit statistical model, the factors associated with caesarean section rates and women's awareness and preference for mode of delivery were compared in centres with and without an increase in midwives density after the implementation of the family physician program. To compare the changes before and after the program, we used the data collected from the same number of women in 2005 as the baseline.

RESULTS

After adjusting for baseline data collected in 2005, the resutls showed no significant change in caesarean section rates and women's awareness and preference for mode of delivery in the centres with and without an increase in midwives density after the implementation of the family physician program. The Matchit model showed a significant mean increase 14%(0.03-0.25) in women's awareness of the benefits of natural childbirth between 2005 and 2013 in health centres where the density of midwives increased compared with health centres where it did not. The difference-in-differences model showed that the odds ratio of women's preference for caesarean section decreased by 41% among participants who were aware of the benefits of natural childbirth, (OR = 0.59, 95% CI: (0.22-0.85); P>0.001).

CONCLUSIONS

The results of this study showed that an increase in the density of midwives in the family physician program led to an increase in women's awareness of the benefits of natural childbirth. An increase in women's awareness of the benefits of natural childbirth was associated with a decreased preference for caesarean section, however this reduction did not have a significant impact on caesarean section rates; possibly, this finding might be attributed to the complexity of this problem that needs a mixed strategy involving various stockholders.

A quasi-experimental design to assess the effectiveness of the federal healthy start in reducing preterm birth among obese mothers

We assessed the impact of Central Hillsborough Healthy Start (CHHS), a federally-funded program dedicated to improving maternal and infant outcomes in a population of high-risk obese mothers in the socio-economically challenged community of East Tampa in Florida on preterm birth and very preterm birth (VPTB). We utilized hospital discharge records linked to vital statistics data in Florida (2004-2007) to study obese women with a singleton birth, matching mothers in the CHHS catchment area with those from the rest of Florida. We conducted conditional logistic regression with the matched data. Obese mothers in the CHHS service area had a 61% lower likelihood of having a VPTB infant than obese mothers in the rest of the state (AOR = 0.39, 95% CI 0.21-0.70). Obese women of reproductive age may benefit from services from federal Healthy Start programs. Study findings underscore the need for further research to explore the impact of such programs.

The effects of breastfeeding exclusivity on early childhood outcomes

OBJECTIVES

We examined the relationship between breastfeeding exclusivity and duration and children's health and cognitive outcomes at ages 2 and 4 years.

METHODS

We used the Early Childhood Longitudinal Study-Birth Cohort, a nationally representative sample of 10,700 children born in the United States in 2001. Parent interviews and child assessments were conducted in measurement waves at 9 months, 2 years, 4 years, and in kindergarten, with the focus on ages 2 and 4 years. We employed propensity scores as a means of adjusting for confounding involving observed characteristics.

RESULTS

Outcome analyses using propensity scores showed some small effects of breastfeeding on key outcomes at age 4 years but not at age 2 years. Effects appeared to be concentrated in reading and cognitive outcomes. Overall, we found no consistent evidence for dosage effects of breastfeeding exclusivity. Our sensitivity analyses revealed that a small amount of unobserved confounding could be responsible for the resulting benefits.

CONCLUSIONS

Our study revealed little or no effect of breastfeeding exclusivity and duration on key child outcomes.

The impact of SLHS program on perinatal indicators

The federal Healthy Start program began 20 years ago, yet outcome evaluations lack sufficient rigor to draw conclusions on program impact. We evaluated the impact of the Healthy Start program on birth outcomes, prenatal care, and public services utilization. Birth record data for the St. Louis Healthy Start Program (SLHS) and non-SLHS controls (matched using a propensity score technique) were assessed for differences. Propensity score matching techniques matched SLHS to non-SLHS clients on potentially confounding variables for births from years 2006 to 2008. Traditional multivariable logistic regression on the full, unmatched sample was also conducted for comparison. Matching eliminated any prior statistical differences between groups on covariates. 168 controls and 84 SLHS participants remained in the final matched analysis group. Both analysis techniques were similar on all outcomes, revealing significant group differences for low birth weight (matched OR = 0.28, p = 0.023) and prematurity (matched OR = 0.25, p = 0.012) but not for prenatal care (matched OR = 0.76, p = 0.414), or public services utilization (matched OR = 3.31, p = 0.121). Early results for this Healthy Start project are positive in key areas directly impacting infant mortality. However, continued analysis of this program for sustained impact in these areas and ultimately, a reduction in infant mortality is needed. Additionally, more rigorous experimental and quasi-experimental evaluation designs are needed to assess the impact of other Healthy Start programs around the country.

Breast milk and cognitive development--the role of confounders: a systematic review

OBJECTIVES

The association between breastfeeding and child cognitive development is conflicted by studies reporting positive and null effects. This relationship may be confounded by factors associated with breastfeeding, specifically maternal socioeconomic class and IQ.

DESIGN

Systematic review of the literature.

SETTING AND PARTICIPANTS

Any prospective or retrospective study, in any language, evaluating the association between breastfeeding and cognitive development using a validated method in healthy term infants, children or adults, was included.

PRIMARY AND SECONDARY OUTCOME MEASURES

Extracted data included the study design, target population and sample size, breastfeeding exposure, cognitive development assessment tool used and participants' age, summary of the results prior to, and following, adjustment for confounders, and all confounders adjusted for. Study quality was assessed as well.

RESULTS

84 studies met our inclusion criteria (34 rated as high quality, 26 moderate and 24 low quality). Critical assessment of accepted studies revealed the following associations: 21 null, 28 positive, 18 null after adjusting for confounders and 17 positive-diminished after adjusting for confounders. Directionality of effect did not correlate with study quality; however, studies showing a decreased effect after multivariate analysis were of superior quality compared with other study groupings (14/17 high quality, 82%). Further, studies that showed null or diminished effect after multivariate analysis corrected for significantly more confounders (7.7±3.4) as compared with those that found no change following adjustment (5.6±4.5, p=0.04). The majority of included studies were carried out during childhood (75%) and set in high-income countries (85.5%).

CONCLUSIONS

Much of the reported effect of breastfeeding on child neurodevelopment is due to confounding. It is unlikely that additional work will change the current synthesis. Future studies should attempt to rigorously control for all important confounders. Alternatively, study designs using sibling cohorts discordant for breastfeeding may yield more robust conclusions.

Duration of breastfeeding and childhood obesity: a generalized propensity score approach

OBJECTIVE

To estimate the effect of breastfeeding duration on childhood obesity.

DATA SOURCE

The Child Development Supplement (CDS) of the Panel Study of Income Dynamics (PSID). The PSID provides extensive data on the income and well-being of a representative sample of U.S. families from 1968 to the present. The CDS collects information on the children in PSID families ranging from cognitive, behavioral, and health status to their family and neighborhood environment. The first two waves of the CDS were conducted in 1997 and 2002, respectively. The data provide information on 3,271 children and their mothers.

STUDY DESIGN

We use the generalized propensity score to adjust for confounding based on continuous treatment, and the general additive model to analyze the adjusted association between treatment and the outcome conditional on the propensity score. The main outcome is the body mass index (BMI) directly assessed during the in-person interview in 2002. Covariates include family, maternal, and child characteristics, many of which were measured in the year the child was born.

PRINCIPAL FINDINGS

After using propensity scores to adjust for confounding, the relationship between breastfeeding duration and childhood BMI is trivially small across a range of model specifications, and none of them is statistically significant except the unadjusted model.

CONCLUSIONS

The causal link between duration of breastfeeding and childhood obesity has not been established. Any recommendation of promoting breastfeeding to reduce childhood obesity is premature.

Dietary patterns at 6, 15 and 24 months of age are associated with IQ at 8 years of age

Diet supplies the nutrients needed for the development of neural tissues that occurs over the first 2 years of life. Our aim was to examine associations between dietary patterns at 6, 15 and 24 months and intelligence quotient (IQ) scores at 8 years. Participants were enrolled in an observational birth cohort (ALSPAC study, n = 7,097). Dietary data was collected by questionnaire and patterns were extracted at each time using principal component analysis. IQ was measured using the Wechsler Intelligence Scale for Children at 8 years. Associations between dietary patterns and IQ were examined in regression analyses adjusted for potential confounding and by propensity score matching, with data imputation for missing values. At all ages, higher scores on a Discretionary pattern (characterized by biscuits, chocolate, sweets, soda, crisps) were associated with 1-2 point lower IQ. A Breastfeeding pattern at 6 months and Home-made contemporary patterns at 15 and 24 months (herbs, legumes, cheese, raw fruit and vegetables) were associated with 1-to-2 point higher IQ. A Home-made traditional pattern (meat, cooked vegetables, desserts) at 6 months was positively associated with higher IQ scores, but there was no association with similar patterns at 15 or 24 months. Negative associations were found with patterns characterized by Ready-prepared baby foods at 6 and 15 months and positive associations with a Ready-to-eat foods pattern at 24 months. Propensity score analyses were consistent with regression analyses. This study suggests that dietary patterns from 6 to 24 months may have a small but persistent effect on IQ at 8 years.