Reduced Risk of Neonatal Respiratory Infections Among Breastfed Girls but Not Boys

Abstract

ABSTRACT.Objective. The effect of breastfeeding on community-acquired neonatal infections has not been well studied, although the neonatal period is one of special vulnerability to infectious pathogens. Respiratory tract infections are the neonatal infection most commonly diagnosed after nursery discharge. We therefore chose respiratory tract infections diagnosed after nursery discharge as representative of neonatal community-acquired infection and studied the impact of breastfeeding on this neonatal infection syndrome.Methods. An unmatched nested case-control study was performed within a previously defined study cohort of 13 224 mother-infant pairs delivering between October 1, 1990, and March 31, 1998. Infants who were delivered at < 37 weeks' gestation were excluded. Neonatal respiratory tract infections were defined using modified National Nosocomial Infections Surveillance System criteria and were included in the case series when diagnosed after nursery discharge and at age <30 days. Infant feeding status during the first month of life was ascertained using automated text search of electronic medical records and was categorized as exclusive breastfeeding, mixed feeding, or exclusive formula feeding.Results. A total of 241 neonatal respiratory tract infections were found, and 1205 control subjects were selected. Compared with control subjects, case infants were more often born during the winter respiratory syncytial virus season (48% vs 33%), more likely to have a sibling present (70% vs 54%), and more likely to be a member of a socioeconomically at-risk family (24% vs 18%). Case patients were less likely to be exclusively breastfed (38% vs 44%) and equally likely to be exposed to mixed feeding (35% vs 34%) relative to control subjects. When compared with formula feeding only, the odds ratio (OR) of exclusive breastfeeding was 0.70 (95% confidence interval [CI]: 0.49 -0.99) and that of mixed feeding was 0.83 (95% CI: 0.58 -1.2). However, when stratified by infant sex, the inverse association between breastfeeding and risk of neonatal respiratory tract infection was confined to neonatal girls, for whom the unadjusted ORs associated with breastfeeding only and mixed feeding were 0.5 (95% CI: 0.29 -0.78) and 0.6 (95% CI: 0.35-0.93), respectively. There was no meaningful association between breastfeeding and risk of neonatal respiratory tract infection among neonatal boys, for whom the unadjusted ORs associated with breastfeeding only and mixed feeding were 1.1 (95% CI: 0.63-1.8) and 1.3 (95% CI: 0.74 -2.1), respectively. After adjustment for year of birth, season of birth, siblings, and socioeconomic status, both exclusive breastfeeding and mixed feeding remained protective among girls, with ORs of 0.5 (0.29 -0.78) and 0.6 (0.34 -0.93), respectively. The corresponding ORs for boys were 1.1 (0.64 -2.0) and 1.4 (0.78 -2.4).Conclusions. charge, 6 and they are typically not caused by congenital structural anomalies, as might be the case for other syndromes such as urinary tract infections. We therefore chose respir...

Effect of breastfeeding on asthma, lung function and bronchial hyperreactivity in ISAAC Phase II

“…This observation is in agreement with another report concerning neonatal respiratory infections [33]. Other environmental factors, such as diet, infections or hormones, may further contribute to sex-specific patterns of associations between breastfeeding, asthma and allergies [34].…”

Effect of Breastfeeding on Lung Function in Childhood and Modulation by Maternal Asthma and Atopy

“…Human milk is uniquely suited to the feeding of infants, having been subjected to selective pressures for millennia. There are multiple well-documented benefits of breastfeeding, such as improved neural development (46,47) and reduced number of infections (1,3,4,39,48). For children of nonasthmatic mothers, this analysis demonstrates a further benefit of breastfeeding-that is, that longer breastfeeding is associated with enhanced lung growth.…”

“…Infants with narrower airways are known to be more prone to wheeze during viral infections (18), and we thus hypothesized that TGF-b in milk could enhance lung and airway growth. However, children with asthma have, as a group, evidence of chronic airway obstruction, as shown by their lower mean values for FEV 1 and FEV 1 /FVC ratio (19,20), and the level of airway obstruction is strongly and directly associated with severity and persistence of the disease (20,21). We thus reasoned that breastfeeding could have differential effects on lung and airway growth, depending on the asthma status of the mother, and that these effects could persist until the school years.…”

Human Rhinoviruses in Severe Respiratory Disease in Very Low Birth Weight Infants

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