Long-term Effects Of Breastfeeding Research Articles

Breastfeeding duration is associated with larger cortical gray matter volumes in children from the ABCD study.

Despite the numerous studies in favor of breastfeeding for its benefits in cognition and mental health, the long-term effects of breastfeeding on brain structure are still largely unknown. Our main objective was to study the relationship between breastfeeding duration and cerebral gray matter volumes. We also explored the potential mediatory role of brain volumes on behavior. We analyzed 7,860 magnetic resonance images of children 9-11 years of age from the Adolescent Brain Cognitive Development (ABCD) dataset in order to study the relationship between breastfeeding duration and cerebral gray matter volumes. We also obtained several behavioral data (cognition, behavioral problems, prodromal psychotic experiences, prosociality, impulsivity) to explore the potential mediatory role of brain volumes on behavior. In the 7,860 children analyzed (median age=9 years and 11 months; 49.9% female), whole-brain voxel-based morphometry analyses revealed an association mainly between breastfeeding duration and larger bilateral volumes of the pars orbitalis and the lateral orbitofrontal cortex. In particular, the association with the left pars orbitalis and the left lateral orbitofrontal cortex proved to be very robust to the addition of potentially confounding covariates, random selection of siblings, and splitting the sample in two. The volume of the left pars orbitalis and the left lateral orbitofrontal cortex appeared to mediate the relationship between breastfeeding duration and the negative urgency dimension of the UPPS-P Impulsive Behavior Scale. Global gray matter volumes were also significant mediators for behavioral problems as measured with the Child Behavior Checklist. Our findings suggest that breastfeeding is a relevant factor in the proper development of the brain, particularly for the pars orbitalis and lateral orbitofrontal cortex regions. This, in turn, may impact impulsive personality and mental health in early puberty.

Children’s Health Capital Investment: Effects of U.S. Infant Breastfeeding on Teenage Obesity

Obesity, as a health and social problem with rising prevalence and soaring economic cost, is increasingly drawing scholarly and public policy attention. While many studies have suggested that infant breastfeeding protects against childhood obesity, empirical evidence on this causal relationship is fragile. Using the health capital development theory, this study exploited multiple data sources from the U.S. and a three-way error components model (ECM) with a jackknife resampling plan to estimate the effect of in-hospital breastfeeding initiation and breastfeeding for durations of 3, 6, and 12 months on the prevalence of obesity during teenage years. The main finding was that a 1% rise in the in-hospital breastfeeding initiation rate reduces the teenage obesity prevalence rate by 1.7% (9.6% of a standard deviation). The magnitude of this effect declines as the infant breastfeeding duration lengthens—e.g., the 12-month infant breastfeeding duration rate is associated with a 0.53% (3.7% of a standard deviation) reduction in obesity prevalence in the teenage years (9th to 12th grades). The study findings agree with both the behavioral and physiological theories on the long-term effects of breastfeeding, and have timely implications for public policies promoting infant breastfeeding to reduce the economic burden of teenage and later adult-stage obesity prevalence rates.

Polish Women Have Moderate Knowledge of Gestational Diabetes Mellitus and Breastfeeding Benefits.

Gestational diabetes mellitus (GDM) is a multifaceted disease and is associated with complications for newborns and mothers. The aim of the study was to assess Polish women’s knowledge concerning GDM and their attitude to breastfeeding. As a research tool, an anonymous online survey that included 33 questions, grouped into three main sections—sociodemographic and obstetric variables, risk factors for GDM and neonatal adverse outcomes, and knowledge about breastfeeding—was used and administered online. A total of 410 women aged from 18 to 45 participated in this study. Based on the survey, it was demonstrated that the women had moderate knowledge concerning the maternal risk factors and adverse neonatal outcomes associated with GDM and, additionally, the short- and long-term effects of breastfeeding. Significantly deeper knowledge about GDM, including breastfeeding by GDM mothers, was observed among hyperglycemic mothers in comparison to normoglycemic mothers. However, knowledge concerning the health benefits of breastfeeding was not related to the mothers’ glycemic status. In conclusion, educational programs must include pre-pregnancy education of women and place emphasis on explaining the mechanism of development of GDM and the transformation of GDM to type 2 diabetes. This is crucial for changing the public’s perception of GDM as a temporary, reversible clinical entity.

Recovery of the maternal skeleton after lactation is impaired by advanced maternal age but not by reduced IGF availability in the mouse.

Lactation results in substantial maternal bone loss that is recovered following weaning. However, the mechanisms underlying this recovery, and in particular the role of insulin-like growth factor 1 (IGF-I), is not clear. Furthermore, there is little data regarding whether recovery is affected by advanced maternal age. Using micro-computed tomography, we studied bone recovery following lactation in mice at 2, 5 and 7 months of age. We also investigated the effects of reduced IGF-I availability using mice lacking PAPP-A2, a protease of insulin-like growth factor binding protein 5 (IGFBP-5). In 2 month old mice, lactation affected femoral trabecular and cortical bone, but only cortical bone showed recovery 3 weeks after weaning. This recovery was not affected by deletion of the Pappa2 gene. The amount of trabecular bone was reduced in 5 and 7 month old mice, and was not further reduced by lactation. However, the recovery of cortical bone was impaired at 5 and 7 months compared with at 2 months. Recovery of the maternal skeleton after lactation is impaired in moderately-aged mice compared with younger mice. Our results may be relevant to the long-term effects of breastfeeding on the maternal skeleton in humans, particularly given the increasing median maternal age at childbearing.

Breastfeeding duration is associated with offspring's adherence to prudent dietary pattern in adulthood: results from the Nutritionist's Health Study.

Little is known about the long-term effect of breastfeeding on dietary habits. We examined the association between breastfeeding duration and adherence to current dietary patterns of young women. This was a cross-sectional analysis of 587 healthy women aged ≤45 years, undergraduates or nutrition graduates. Maternal characteristics and breastfeeding duration [<6; 6-<12; ≥12 months (reference)] were recalled. Diet was assessed using a food frequency questionnaire and patterns were identified using factor analysis by principal component. Adherence to patterns was categorized in tertiles; the first (T1 = reference) was compared to T2 + T3 (moderate-to-high adherence). Logistic regression was performed considering the minimal sufficient adjustment recommended by the directed acyclic graph. Median age was 22 (interquartile range (IQR) 20; 27) years and body mass index (BMI) 22.2 (IQR 20.4; 25.0) kg/m2. The four dietary patterns identified (Processed, Prudent, Brazilian and Lacto-vegetarian) explained 27% of diet variance. Women breastfed for <6 months showed lower chance of moderate-to-high adherence to the Prudent pattern (odds ratio (OR) = 0.53, p = 0.04). Breastfeeding was not associated with the other patterns. Maternal pre-pregnancy BMI was directly associated with moderate-to-high adherence to the Processed pattern (OR = 2.01, p = 0.03) and inversely to the Prudent pattern (OR = 0.52, p = 0.02). Higher adherence to the Brazilian pattern was associated with proxies of low socioeconomic status and the Lacto-vegetarian pattern with the opposite. Confirmation in prospective studies of the association found in this study between breastfeeding with the Prudent pattern in adult offspring could suggest that early feeding practices influence long-term dietary habits, which could then affect the risk of nutrition-related diseases.

Analysis of healthy breast tissue from Komen Tissue Bank shows distinct histology, decreased proliferation, and lower periductal collagen deposition in women with prolonged history of breastfeeding.

1538 Background: Epidemiological studies have shown that prolonged breastfeeding is associated with a reduced risk of developing triple negative/basal-like breast cancer (TN/BLBC). We have modeled abrupt involution (AI) following short breastfeeding and gradual involution (GI) of the mammary gland that occurs over time upon prolonged breastfeeding in wild-type FVB/N mice and discovered prominent histological and molecular changes in the AI glands over time. Further, we demonstrated that breast tissue from healthy women who breastfed &lt;6 months showed enrichment in stem-cell and cell renewal pathways. Here, we corroborate those studies using normal human breast tissue obtained from Susan G. Komen for the Cure Tissue Bank (KTB). Methods: FFPE breast tissue sections obtained from KTB (Protocol #2017CO184). Donors were parous women, aged 18 to 45, without history of breast cancer and for whom breastfeeding history was available. H&amp;E sections and TDLU, the primary anatomical source of most breast cancers, of women who breastfed for ≥6 months (GI, n=49) vs. those who breastfed for ≤3 months (AI, n=20) were evaluated by a blinded pathologist. Masson Trichrome stain was used to measure collagen deposition. Ki67 immunohistochemistry was utilized to determine proliferation. Statistical significance was measured using Fisher’s exact t-test and two-sample t-test with a p-value of &lt;0.05. Results: H&amp;E analysis revealed that breast tissue obtained from women in the AI cohort exhibited histological features of inflammation (p-value= 0.025). Using Ki67 IHC (AI, n=15; GI, n=32) and Masson Trichome stain (AI, n=3; GI, n=4), sections in the AI cohort showed 2-fold increase in proliferation of lobular epithelium (p-value= 0.048) and 1.4-fold increase in periductal collagen deposition (p-value= 0.027) when compared to GI cohort. Age, race, and BMI were not statistically different between AI and GI cohorts. Conclusions: Breast tissue from parous women who breastfed ≤3 months is histologically different than tissue of women with ≥6 months history of breastfeeding. We are currently staining more breast tissue samples obtained from KTB. Experiments are underway to assess the long-term effect of breastfeeding on breast epithelial cell hierarchy and biomarkers of inflammation. Understanding this mechanistic link will help in developing prevention strategies, particularly for African-American women who have lower prevalence of breastfeeding and higher incidence of TN/BLBC.

Peripartum dietary supplementation of a small-molecule inhibitor of tryptophan hydroxylase 1 compromises infant, but not maternal, bone.

Long-term effects of breastfeeding on maternal bone are not fully understood. Excessive maternal bone loss stimulated by serotonin signaling during lactation may increase bone fragility later in life. We hypothesized that inhibiting nonneuronal serotonin activity by feeding a small-molecule inhibitor of the rate-limiting enzyme in serotonin synthesis [tryptophan hydroxylase 1 (TPH1)] would preserve maternal bone postweaning without affecting neonatal bone. Chow supplemented with the small-molecule TPH1 inhibitor LP778902 (~100 mg/kg) or control chow was fed to C57BL/6 dams throughout pregnancy and lactation, and blood was collected on days 1 and 21 of lactation. Dams returned to a common diet postweaning and were aged to 3 or 9 mo postweaning. Pups were euthanized at weaning. The effect of TPH1 inhibition on dam and pup femoral bone was determined by micro-computed tomography. Peripartum dietary supplementation with LP778902 decreased maternal serum serotonin concentrations ( P = 0.0007) and reduced bone turnover, indicated by serum NH2-terminal propeptide of type I collagen ( P = 0.01) and COOH-terminal collagen cross-links ( P = 0.02) concentrations, on day 21 of lactation. Repressed bone turnover from TPH1 inhibition was not associated with structural changes in maternal femur at 3 or 9 mo postweaning. By contrast, neonates exposed to peripartum LP778902 demonstrated differences in trabecular and cortical femoral bone compared with pups from control dams, with fewer ( P = 0.02) and thinner ( P = 0.001) trabeculae as well as increased trabecular spacing ( P = 0.04). Additionally, cortical porosity was increased ( P = 0.007) and cortical tissue mineral density was decreased ( P = 0.005) in pups of LP778902-treated dams. Small-molecule TPH1 inhibitors should be carefully considered in pregnant and lactating women, given potential risks to neonatal bone development.

Breastfeeding during infancy and neurocognitive function in adolescence: 16-year follow-up of the PROBIT cluster-randomized trial.

BackgroundEvidence on the long-term effect of breastfeeding on neurocognitive development is based almost exclusively on observational studies. In the 16-year follow-up study of a large, cluster-randomized trial of a breastfeeding promotion intervention, we evaluated the long-term persistence of the neurocognitive benefits of the breastfeeding promotion intervention previously observed at early school age.Methods and findingsA total of 13,557 participants (79.5% of the 17,046 randomized) of the Promotion of Breastfeeding Intervention Trial (PROBIT) were followed up at age 16 from September 2012 to July 2015. At the follow-up, neurocognitive function was assessed in 7 verbal and nonverbal cognitive domains using a computerized, self-administered test battery among 13,427 participants. Using an intention-to-treat (ITT) analysis as our prespecified primary analysis, we estimated cluster- and baseline characteristic-adjusted mean differences between the intervention (prolonged and exclusive breastfeeding promotion modelled on the Baby-Friendly Hospital Initiative) and control (usual care) groups in 7 cognitive domains and a global cognitive score. In our prespecified secondary analysis, we estimated mean differences by instrumental variable (IV) analysis to account for noncompliance with the randomly assigned intervention and estimate causal effects of breastfeeding. The 16-year follow-up rates were similar in the intervention (79.7%) and control groups (79.3%), and baseline characteristics were comparable between the two. In the cluster-adjusted ITT analyses, children in the intervention group did not show statistically significant differences in the scores from children in the control group. Prespecified additional adjustment for baseline characteristics improved statistical precision and resulted in slightly higher scores among children in the intervention for verbal function (1.4 [95% CI 0.3–2.5]) and memory (1.2 [95% CI 0.01–2.4]). IV analysis showed that children who were exclusively breastfed for ≥3 (versus <3) months had a 3.5-point (95% CI 0.9–6.1) higher verbal function, but no differences were observed in other domains. While our computerized, self-administered cognitive testing reduced the cluster-level variability in the scores, it may have increased individual-level measurement errors in adolescents.ConclusionsWe observed no benefit of a breastfeeding promotion intervention on overall neurocognitive function. The only beneficial effect was on verbal function at age 16. The higher verbal ability is consistent with results observed at early school age; however, the effect size was substantially smaller in adolescence.PROBIT trial registrationClinicalTrials.gov NCT01561612

Evaluating the efficacy of breastfeeding guidelines on long-term outcomes for allergic disease.

WHO guidelines advocate breastfeeding for 6 months, and EAACI guideline recommends exclusive breastfeeding for 4-6 months. However, evidence for breastfeeding to prevent asthma and allergic disease is conflicting. We examined whether following recommended breastfeeding guidelines alters the long-term risks of asthma, eczema, rhinitis or atopy. The effect of nonexclusive (0, >0-6, >6 months) and exclusive breastfeeding (0, >0-4, >4 months) on repeated measures of asthma (10, 18 years), eczema, rhinitis, and atopy (1-or-2, 4, 10, 18 years) risks was estimated in the IoW cohort (n = 1456) using log-linear models with generalized estimating equations. The Food Allergy and Intolerance Research (FAIR) cohort (n = 988), also from the IoW, was examined to replicate results. Breastfeeding (any or exclusive) had no effect on asthma and allergic disease in the IoW cohort. In the FAIR cohort, any breastfeeding for >0-6 months protected against asthma at 10 years (RR = 0.50, 95% CI = 0.32-0.79, P = 0.003), but not other outcomes, whilst exclusive breastfeeding for >4 months protected against repeated rhinitis (RR = 0.36, 95% CI = 0.18-0.71, P = 0.003). Longer breastfeeding was protective against late-onset wheeze in the IoW cohort. The protective effects of nonexclusive and exclusive breastfeeding against long-term allergic outcomes were inconsistent between these colocated cohorts, agreeing with previous observations of heterogeneous effects. Although breastfeeding should be recommended for other health benefits, following breastfeeding guidelines did not appear to afford a consistent protection against long-term asthma, eczema, rhinitis or atopy. Further research is needed into the long-term effects of breastfeeding on allergic disease.

Long-Term Effects of Breastfeeding on Children's Hospitalization for Respiratory Tract Infections and Diarrhea in Early Childhood in Japan.

Whether or not the protective effects of breastfeeding last during or after a shift to a weaning diet is not clear. In the present study, we examined the effects of breastfeeding on hospitalization for respiratory tract infections and diarrhea in early childhood in Japan. Data were extracted from a nationwide longitudinal survey of Japanese children. We restricted the study participants to singleton children who were born after 37 gestational weeks and whose information on feeding practice during infancy were included (n = 43,367). We used logistic regression models to evaluate the associations of breastfeeding with hospitalization for the two diseases among young children (i.e., between ages 6 and 18 months, between ages 18 and 30 months, and between ages 30 and 42 months, respectively), adjusting for children's factors (sex, birth weight, childcare attendance and presence of siblings) and maternal factors (educational attainment and smoking status). Breastfeeding compared with infant formula was not associated with reduced risk of hospitalization for diarrhea during the periods we examined. Although breastfeeding was not associated with reduced risk of hospitalization for respiratory tract infections between ages 6 and 18 months, breastfeeding showed protective effects after that period: the adjusted odds ratios (95% confidence intervals) of exclusive breastfeeding were 0.82 (0.66-1.01) between ages 18 and 30 months and 0.76 (0.58-0.99) between ages 30 and 42 months. Breastfeeding may have long-term protective effects on hospitalization for respiratory tract infections after infancy, but not for diarrhea.

The protective effects of breastfeeding on chronic non-communicable diseases in adulthood: A review of evidence

Chronic non-communicable diseases (NCDs), including cardiovascular diseases, cancers, chronic respiratory diseases, diabetes, etc., are the major causes of mortality in the world, notably in low- and middle-income countries. A growing body of evidence suggests that NCDs have a complex etiology resulting from the interaction of genetic factors, gender, age, ethnicity, and the environmental factors. It is well-documented that chronic diseases in adulthood origins in early life. In recent years, much attention has been focused on primordial and primary prevention of NCD risk factors. There are many biological and epidemiological studies on beneficial effects of breastfeeding during infancy on chronic diseases in adulthood, particularly on hypertension, obesity, diabetes, hypercholesterolemia, and cardiovascular diseases. This review article aims to summarize the current literature on the long-term effects of breastfeeding on prevention of NCDs and their risk factors.The current literature is controversial about these effects; however, a growing body of evidence suggests that breastfeeding has protective roles against obesity, hypertension, dyslipidemia, and type II diabetes mellitus during adulthood. In addition to its short-term benefits, encouraging breastfeeding can have long-term beneficial health effects at individual and population levels.

Effect of duration of breastfeeding on neuropsychological development at 10 to 12 years of age in a cohort of healthy children

The aim of this article was to explore the effect of duration of breastfeeding on neurocognitive development. The long-term effect of breastfeeding on neurodevelopment was examined through a battery of neuropsychological tests in 1403 children (693 females, 710 males; mean age 11 y 9mo [SD 6mo], range: 10y 3mo-12y 8mo) who were originally recruited at 6 to 12 weeks of age for a clinical trial on acellular pertussis vaccines. An estimated IQ was obtained from scores of the vocabulary, similarities, block design, and coding tests. Breastfeeding data had been prospectively collected throughout the first year of life. Duration of exclusive breastfeeding was defined as the time during which children received breast milk without receiving any supplemental formula or food. Children were assessed at 10 to 12 years of age. We adjusted the analysis on test scores for multiple potential confounders. Multivariate analysis showed a significant association between exclusive breastfeeding duration and test scores in the vocabulary (odds ratio [OR] 0.05; confidence interval [CI] 0.00-0.10; p=0.04) and similarities (OR 0.06; CI 0.01-0.11; p=0.03) tests. These associations have a negligible effect size, however. Scores on one writing praxis test subcategory decreased with increasing duration of both exclusive breastfeeding (OR -0.06; CI -0.11 to -0.01; p=0.03) and breastfeeding irrespective of consumption of other foods (OR -0.06; CI -0.11 to -0.01; p=0.03). A negative association was also found between one subcategory of the California verbal learning test and breastfeeding duration longer than 6 months (OR -0.21; CI -0.42 to -0.01; p=0.04). Breastfed healthy children may perform better on neuropsychological tests in the language domain at 10 to 12 years of age. However, the effect of breast milk on neuropsychological performance in healthy children may have a limited clinical relevance and is confounded by parental education.

The Long-Term Effects of Breastfeeding on Child and Adolescent Mental Health: A Pregnancy Cohort Study Followed for 14 Years

The Long-Term Effects of Breastfeeding on Child and Adolescent Mental Health: A Pregnancy Cohort Study Followed for 14 Years

Personalschulung als Interventionsansatz auf Klinikebene zur Stillförderung: Evaluationsergebnisse der ersten Phase der STELLA-Studie

The health-promoting short- and long-term effects of breast-feeding are supported by a vast scientific literature. The Bavarian prospective cohort study 2005/2006 showed regional variations of breast-feeding rates. Furthermore, improvement in counselling mothers, particularly with regard to prevention and handling of breast-feeding problems, has a great potential for health promotion. The objective of this study is to promote breast-feeding in maternity clinics by improving the surrounding conditions. A clinic-based and community-related intervention trial was carried out in Lower Bavaria as a model region with below average breast-feeding rates. (1) INTERVENTION: an advanced training of maternity ward professionals of 10 hospitals and after-care midwives was performed from May until December 2008. The training programme was based on the WHO/UNICEF criteria of the "Ten Steps to Successful Breastfeeding" to deepen the breast-feeding knowledge and to improve the breast-feeding management. (2) EVALUATION: A singular assessment of the advanced training programme was undertaken concerning an increase of knowledge and the practicability in clinical everyday life by participants; improvements of the maternity wards were assessed via structural interviews with maternity ward staff before and after intervention. Approximately 85% (n=378) of the staff of the 10 maternity clinics attended the training course. The survey after the training programme (response rate 83%) indicated that more than 80% of the participants stated to have learned something new and to be able to use the knowledge acquired for their own practice. Results of the clinic interviews showed a transfer of training contents into clinical work routines. Improvements at interview date were shown best for bonding (all 10 maternity clinics), for additional feeding (8 maternity clinics) as well as for 24-h rooming-in and mother counselling (7 maternal clinics each). Training of maternity ward professionals accounts for baby-friendly conditions in maternity clinics. Most willingness for improvements was shown by maternity ward staff particularly for bonding between mother and child as well as for additional feeding. Considerable differences between the hospitals were observed for the promotion of infant formulas before and after the intervention.

Typical Leptin Fall Is Mitigated by Breastfeeding in Female Infants

Programming of the nutritional and hormonal status of offspring occurs mostly during the gestational and breastfeeding periods. Several studies have reported that breastfed children are more protected from developing obesity in adult life; however, the mechanism that explains this phenomenon is not clear. We undertook this study to evaluate if weight, gender or feeding mode (breastfed or formula-fed) affects leptin levels (during the first 3 months after birth) in a cohort of term newborns, the Breastfeeding Cohort. A cohort of 99 term newborns divided into four groups according to gender and feeding type: breastfed female, formula-fed female, breastfed male and formula-fed male were studied. Feeding mode was freely chosen by the parents. Blood sampling for glucose, insulin and leptin was performed at birth and after 3 months. No differences were found among the groups for maternal age, marital status, educational and socioeconomic level, maternal occupation, and prenatal care. No statistically significant differences were found for weight, length or body mass index at birth among the four groups. There were differences in leptin with a higher level in girls (0.907 ± 0.332) than boys (0.663 ± 0.351; p <0.001) at birth and at 3 months (0.618 ± 0.225, 0.464 ± 0.195; p <0.0001). A decrease in leptin levels from birth to 3 months was observed in all groups with the exception of breastfed females (0.849 ± 0.352-0.672 ± 0.222, p = NS). In our study, breastfed females were protected from this fall in serum leptin levels. Our findings support further studies on the long-term effects of breastfeeding.

Adipokines in breast milk and preterm infants

Studies have shown that the early life environment affects feeding behaviour, food intake and energy balance in later life, suggesting there is a link between foetal and infant growth and the risk of metabolic disorders in adulthood. Although there is an evident epidemiological association between low birth weight and adult-onset diseases, the incidence of metabolic diseases in adulthood among people who were born prematurely is still unknown. Considerable advances have been made during the last years in the scientific knowledge of the benefits of early nutrition, such as breastfeeding, on health and well-being later in life. Nutritional researchers have focussed their attention on the biological characteristics of human breast milk, which represents the main source of nutrients in the first months of life for breastfed infants. Recently, leptin and ghrelin have been detected in the breast milk of mothers of term and preterm infants. Adiponectin and resistin, present in term human milk, have not been investigated in the breast milk of mothers of preterm infants. These hormones are involved in the regulation of energy balance and may have a role in the regulation of growth and development in the neonatal period and infancy, as well as long-term effects on metabolic programming. Leptin, adiponectin and resistin have been found at lower levels in pre-term infants compared with term newborns, whereas there seems to be no difference in ghrelin levels. Future research is necessary to clarify the role of hormones present in breast milk for identifying potential short- and long-term effects of breastfeeding on the health of children born prematurely.

The Long-Term Effects of Breastfeeding on Child and Adolescent Mental Health: A Pregnancy Cohort Study Followed for 14 Years

To determine whether there was an independent effect of breastfeeding on child and adolescent mental health. The Western Australian Pregnancy Cohort (Raine) Study recruited 2900 pregnant women and followed the live births for 14 years. Mental health status was assessed by the Child Behaviour Checklist (CBCL) at 2, 6, 8, 10, and 14 years. Maternal pregnancy, postnatal, and infant factors were tested in multivariable random effects models and generalized estimating equations to examine the effects of breastfeeding duration on mental health morbidity. Breastfeeding for less than 6 months compared with 6 months or longer was an independent predictor of mental health problems through childhood and into adolescence. This relationship was supported by the random effects models (increase in total CBCL score: 1.45; 95% confidence interval 0.59, 2.30) and generalized estimating equation models (odds ratio for CBCL morbidity: 1.33; 95% confidence interval 1.09, 1.62) showing increased behavioral problems with shorter breastfeeding duration. A shorter duration of breastfeeding may be a predictor of adverse mental health outcomes throughout the developmental trajectory of childhood and early adolescence.

Commentary: Assessing the impact of breastfeeding on child health: where conventional methods alone fall short for reliably establishing causal inference

Given the strong social patterning of both breastfeeding and child health in high-income countries (HICs), there is a high probability of observing associations that are confounded by broader socio-economic factors rather than being due to any biological effects of breastfeeding. Even where extensive adjustments for confounders are made, residual confounding remains a persistant problem. As the exact nature of the relationship between socio-economic position (SEP) and health-related characteristics and disease are complex and not entirely understood, it is difficult to fully capture this in analyses and comprehensively control for confounding by SEP. As such, conventional observational methods, relying on the adjustment of associations for measured confounders, will likely be, on their own, insufficient for reliably establishing causal inference. This is evident, for example, from recent antioxidant trials failing to replicate the results of large-scale observational studies reporting protective effects that were independent of a wide range of confounders. This is the most likely attributable to the presence of residual confounding in the observational studies. With respect to the association between breastfeeding and child obesity, various observational studies have reported decreased risk on child obesity associated with breastfeeding in infancy; however, a meta-analysis indicated that this may be largely due to publication bias and confounding. In contrast, family studies using siblings discordant for breastfeeding duration to control for social, familial and environmental confounding, suggest that associations may not in fact be completely confounded by these factors. Thus, the picture in terms of causal effects of breastfeeding on child obesity is unclear. Ideally, a randomized trial would provide the gold standard for causal inference. However, a trial randomizing mothers to breastfeed or not breastfeed would clearly be unfeasible and unethical. A recent trial of breastfeeding promotion in Belarus has been carried out. This trial resulted in a large increase in exclusive breastfeeding in the intervention group (43.3 vs 6.4%) and a higher prevalence of any breastfeeding at all ages 412 months, but mean adiposity and levels of obesity were similar by randomized group, suggesting that breastfeeding is not causally related to child obesity. It is thus becoming increasingly apparent that combining conventional approaches with additional methods of testing causal inference are required to establish the long-term effects of breastfeeding and other developmental exposures on later life outcomes. Various new methods for improving causal inference in observational studies in general have been advanced, including new statistical approaches, maternal–paternal comparisons, sibling comparisons, Mendelian randomization and other genetically informed studies. However, not all of these will be applicable to breastfeeding, being, for example, specific to prenatal exposures or, where genetic variants are used, it is not clear if an appropriate genetic variant relating to breastfeeding will be available. The study by Kwok et al. using the children of 1997 cohort in this issue of the IJE takes advantage of differences in the confounding structure of breastfeeding and child obesity in Hong Kong compared with Western/European countries (where the majority of existing studies reporting associations on breastfeeding have been carried out) to explore causal inference. As the authors discuss, in high-income populations, individuals of higher SEP are more likely to breastfeed and less likely to have obese children. In contrast, in non-Westernized countries child obesity tends to be less clearly socially patterned and, in Hong Kong in particular, sustained exclusive breastfeeding is more common in less-educated women. This means that if the inverse associations of breastfeeding with adiposity, reported in studies of Western populations, are largely explained by Published by Oxford University Press on behalf of the International Epidemiological Association

Book Review: Evidence on the Long-Term Effects of Breastfeeding

Book Review: Evidence on the Long-Term Effects of Breastfeeding

Long-Term Effects of Breastfeeding, Maternal Smoking During Pregnancy, and Recurrent Lower Respiratory Tract Infections on Asthma in Children

The effect of breastfeeding on asthma is controversial, which may be explained by related and interacting early childhood risk factors. We assessed the joint effects of a risk-triad consisting of maternal smoking during pregnancy, breastfeeding for less than 3 months, and recurrent lower respiratory tract infections (RLRTI) on physician-diagnosed childhood asthma. The association was assessed in the Isle of Wight birth cohort study (1989–1990) using a repeated measurement approach with data collection at birth, and at ages 1, 2, 4, and 10 years. The population consists of 1,456 children recruited between January 1989 and February 1990. Prenatal smoking, breastfeeding for less than 3 months, and recurrent lower respiratory infections (RLRTI) were combined into eight risk-triads. Relative risks (RR) and 95% confidence intervals were estimated with a log-linear model. The risk-triad involving RLRTI in infancy, maternal smoking during pregnancy, and breastfeeding for less than 3 months showed a stronger association with asthma at ages 4 and 10 compared to other risk-triads (RR of 5.79 for any asthma at ages 1, 2, 4, and 10; and 3.1 for asthma at ages 4 and 10). Of the three individual risk factors, RLRTI appeared to be the major driver of the combined effects in the risk-triads. The effect of RLRTI on asthma was modified by breastfeeding. Breastfeeding for ≥ 3 months also attenuated the effect of prenatal smoking on asthma in children without RLRTI. A high proportion of asthma cases in childhood can be prevented by promoting breastfeeding, by preventing smoking during pregnancy, and by avoidance of recurrent lower respiratory tract infections in early childhood.