Breastfeeding is protective against early childhood asthma

Breastfeeding and Childhood Wheeze: Age-Specific Analyses and Longitudinal Wheezing Phenotypes as Complementary Approaches to the Analysis of Cohort Data

Systematic reviews suggest that breastfeeding is associated with a lower risk of asthma, although marked heterogeneity exists. Using UK Millennium Cohort Study data (n = 10,126 children, born 2000-2002), we examined the association between breastfeeding duration and wheezing in the previous year, first for each age group separately (ages 9 months, 3 years, 5 years, 7 years, and 11 years) and then in terms of a longitudinal wheezing phenotype: "early transient" (wheezing any time up to age 5 years but not thereafter), "late onset" (any time from age 7 years but not beforehand), and "persistent" (any time up to age 5 years and any time from age 7 years). The association between breastfeeding and wheeze varied by age (2-sided P for interaction = 0.0003). For example, breastfeeding for 6-9 months was associated with lower odds of wheezing at ages 9 months, 3 years, and 5 years but less so at ages 7 years and 11 years (adjusted odds ratios = 0.73, 0.78, 0.79, 0.84, 1.06, respectively). There was a strong dose-response relationship for breastfeeding per month and early transient wheeze (adjusted odds ratio for linear trend = 0.961, 95% confidence interval: 0.942, 0.980) but no clear trend for late-onset or persistent wheeze. Our results identified heterogeneity in the association between breastfeeding and wheezing according to age at wheezing and wheezing phenotype.

Breastfeeding initiation rates among immigrant women in central Italy between 2006 and 2011

OBJECTIVE

This study was aimed at evaluating differences in breastfeeding initiation rates by maternal place of birth among women giving birth in one of 14 hospitals in Lazio, Italy, between 2006 and 2011.

METHODS

The data on 14 hospitals for this study were taken from a survey on healthy newborns carried out during the month of October each year. It collected information on maternal characteristics and infant feeding during the hospital stay. The exposure variable was maternal place of birth. The outcome variable was infant feeding during hospital stay classified as exclusive breastfeeding, predominant breastfeeding (PBF), complementary feeding or formula feeding. Both a descriptive analysis and a logistic regression on infant feeding (exclusive/PBF versus partial or non-breastfeeding) by maternal place of birth were carried out. The logistic regression model was adjusted for confounding factors. A random effect model was used to take into account the correlation of data among the hospitals.

RESULTS

Among the 6505 mothers included in this study, 18.7% were born in non-industrialized countries. Overall, 64.9% of mothers exclusively breastfed their babies, with lower prevalence among Asiatic mothers. The logistic model confirmed that breastfeeding was lower among infants born to Asian mothers (OR: 0.52; 95% CI: 0.35-0.77) compared with other groups, taking into account the effect of the other variables included in this model. Intracluster correlation was equal to 26%, showing that the hospital's model of care is a strong predictor of the initiation of breastfeeding.

CONCLUSIONS

These data are useful for targeting disadvantaged groups when promoting breastfeeding.

Invited commentary: does neonatal hyperbilirubinemia cause asthma?

In an analysis of data from the US Collaborative Perinatal Project, Huang et al. (Am J Epidemiol. 2013;178(12):1691-1697) report an association between neonatal total serum bilirubin levels and childhood asthma. To consider the implications of this finding, we need to evaluate whether the association is causal. The results do not appear to be due to chance or any obvious biases. It is likely that the observed association is the result of a common cause of both hyperbilirubinemia and asthma (confounding). Polymorphisms in the glutathione S-transferase gene are a potential genetic confounder. The glutathione S-transferase M1-null phenotype has been linked to both neonatal hyperbilirubinemia and asthma in several studies. Before making any changes in practice aimed at lowering peak bilirubin levels to reduce asthma risk, it is vital to determine not only whether the association between higher bilirubin levels and asthma risk is causal, but also whether interventions to reduce peak bilirubin levels (or their duration) are associated with decreased risk of asthma (without evidence of other adverse effects). The study by Huang et al. should encourage further investigation of these questions.