Clinical ContextBreast-feeding appears to be linked with a decreased risk for childhood asthma-related symptoms, according to Fredriksson and colleagues in the November 28, 2007, issue of BMC Pediatrics. However, the influence of a family history of asthma or allergy is not clear. The link between breast-feeding and the risk for asthma might be mediated by atopy or infection.
The current study by Sonnenschein-van der Voort and colleagues, embedded in the population-based prospective cohort Generation R study, described by Jaddoe and colleagues in the November 2010 issue of the European Journal of Epidemiology, assesses the association of duration and exclusiveness of breast-feeding with the risk for asthma-related symptoms in the first 4 years of life and whether the association is mediated by atopic or infectious conditions.
Study Synopsis and PerspectivePreschool children who were not breast-fed or not exclusively breast-fed for 6 months show increased rates of asthma-related symptoms, such as wheezing, shortness of breath, and dry cough, according to a study published online July 20 in the European Respiratory Journal.
Asthma symptoms in children, known to be a leading cause of morbidity, have been linked in previous studies with lower rates of breast-feeding, but the study from researchers in the Netherlands is said to be the first to demonstrate an association between the length of time a child was breast-fed and the number of wheezing episodes the child experiences.
For the study, the researchers evaluated data on 5368 children that was part of the Generation R study, a population-based prospective cohort study of pregnant women and their children from fetal life on in Rotterdam, the Netherlands.
They gathered information on breast-feeding duration, exclusiveness, and asthma-related symptoms, including wheezing, shortness of breath, dry cough, and persistent phlegm.
The results showed that, compared with children who were breast-fed for at least 6 months, those who were never breast-fed were 1.4 and 1.5 times more likely to develop symptoms of wheezing and persistent phlegm, respectively.
In addition, children who were not exclusively breast-fed during the first 4 months of life and were also fed milk or solids during that period also were at higher risks of wheezing, shortness of breath, dry cough, and persistent phlegm in their first 4 years vs those who were exclusively breast-fed in their first 4 months.
Further adjusted analyses indicated that the associations of breast-feeding with asthma-related symptoms were not explained by eczema but, instead, were partly related to lower respiratory tract infections.
Breast-feeding is widely believed to help reduce the risk for asthma in younger children through a mediating effect on atopy and/or infections, the study authors believe.
"Underlying mechanisms might include IgA [immunoglobulin A], cytokines, especially TGF [transforming growth factor]-beta1, and long-chain fatty acids in breast milk that stimulate the infant's immune system," they explained.
"Also, glycans help the innate immune system to inhibit pathogen binding to the host cell target ligand, and changes in the delicate balance between pro- and anti-inflammatory compounds."
The protective effect of breast-feeding, in particular, appears to be related to gut microflora that is changed with breast-feeding, they added.
"The gut microflora is suggested to be different between breastfed and formula fed infants. Compared to breastfed infants, those who receive formula feeding have a more complex microflora with more facultative anaerobes, bacteroides and clostridia at higher levels and frequencies," the study authors write.
"We speculate that this might decrease with increasing exclusivity of breastfeeding, leading to lower infection risk and less wheezing by influencing the development of the immune system. Due to this putative effect on the development of the immune system, infections and asthma-related symptoms might occur less frequent even years after stopping breastfeeding."
The results are in line with previous research showing up to a 2.22-fold increased risk of recurrent wheezing or asthma at the ages of 2 to 6 years among children who were not breast-fed or not exclusively breast-fed until age 4 months.
These new findings add to the previous research by showing a dose-response relationship between breast-feeding and the number of wheezing episodes, said lead author Agnes Sonnenschein-van der Voort, MSc, in a press release.
"The link of duration and exclusiveness of breastfeeding with asthma-related symptoms during the first four years was independent of infectious and atopic diseases," said Dr. Sonnenschein-van der Voort, a researcher with the Erasmus Medical Center in the Netherlands.
"These results support current health policy strategies that promote exclusive breastfeeding for 6 months in industrialized countries. Further studies are needed to explore the protective effect of breastfeeding on the various types of asthma in later life."
Eur Respir J. Published online July 20, 2011.