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

Early-Life Nutrition in Preterm Infants and Risk of Respiratory Infections and Wheezing: A Scoping Review

INTRODUCTION

Preterm birth is a common early-life event that can lead to long-term consequences. The incidence of wheezing, asthma, and respiratory tract infections is higher in children born prematurely than in the general population. The purpose of this review was to synthesize the existing literature on the role of early-life nutrition in the later risk of respiratory morbidities.

METHODS

A scoping review of the literature was performed by searching three online databases. Inclusion criteria were: infants born <37 GWk, comparing human milk versus any other type of milk feeding formulation. Our primary outcomes were wheezing or asthma or respiratory tract infections after discharge. Two authors independently screened the results and extracted study characteristics using a predefined charting form.

RESULTS

Nine articles were included (eight cohort studies and one randomized trial). Four studies supported the protective effect of breastfeeding on wheezing or respiratory infections or both. Four studies did not confirm this association. One study confirmed the protective role of breastfeeding only on the subgroup of girls. There was a high heterogeneity among the included studies, in the type of milk feeding, outcomes, and age at follow-up.

CONCLUSIONS

The current evidence is conflicting. The high heterogeneity and methodological flaws could have influenced the results of the studies. Carefully designed studies are required to define the role of early-life nutrition among preterm infants on their long-term respiratory outcomes.

Human milk feeding and wheeze in Black infants born preterm

OBJECTIVES

To determine the association between human milk exposure at 3 months corrected gestational age and recurrent wheeze in preterm Black infants.

METHODS

This is a secondary analysis of data from the D-Wheeze trial (ClinicalTrials.gov identifier NCT01601847). Associations between human milk feeding at 3 months corrected age and wheezing outcomes were examined by generalized linear models.

RESULTS

Exclusively human milk fed infants (n = 13) had significantly fewer wheezing episodes than formula fed infants (n = 230) (IRR (95% CI) = 0.25 (0.07, 0.89), p = 0.03). There were no hospitalizations in infants receiving exclusive human milk. Receiving any human milk was associated with decreased odds of hospitalization by 12 months corrected age (OR (95% CI) = 0.12 (0.02, 0.79), p = 0.03).

CONCLUSIONS

Exclusive human milk feeding at three months corrected gestational age is associated with decreased number of wheezing episodes in the first year of life in preterm Black infants.

S3 guideline Allergy Prevention

BACKGROUND

The persistently high prevalence of allergic diseases in Western industrial nations and the limited possibilities of causal therapy make evidence-based recommendations for primary prevention necessary.

METHODS

The recommendations of the S3 guideline Allergy Prevention, published in its last version in 2014, were revised and consulted on the basis of a current systematic literature search. The evidence search was conducted for the period 06/2013 - 11/2020 in the electronic databases Cochrane and MEDLINE, as well as in the reference lists of current reviews and through references from experts. The literature found was screened in two filtering processes, first by title and abstract, and the remaining papers were screened in the full text for relevance. The studies included after this were sorted by level of evidence, and the study quality was indicated in terms of potential bias (low/high). The revised recommendations were formally agreed and consented upon with the participation of representatives of the relevant professional societies and (self-help) organizations (nominal group process). Of 5,681 hits, 286 studies were included and assessed.

RESULTS

Recommendations on maternal nutrition during pregnancy and breastfeeding as well as on infant nutrition in the first months of life again play an important role in the updated guideline: Many of the previous recommendations were confirmed by the current data. It was specified that breastfeeding should be exclusive for the first 4 - 6 months after birth, if possible, and that breastfeeding should continue with the introduction of complementary foods. A new recommendation is that supplementary feeding of cow's milk-based formula should be avoided in the first days of life if the mother wishes to breastfeed. Furthermore, it was determined that the evidence for a clear recommendation for hydrolyzed infant formula in non-breastfed infants at risk is currently no longer sufficient. It is therefore currently recommended to check whether an infant formula with proven efficacy in allergy prevention studies is available until the introduction of complementary feeding. Finally, based on the EAACI guideline, recommendations were made for the prevention of chicken egg allergy by introducing and regularly giving thoroughly heated (e.g., baked or hard-boiled) but not "raw" chicken egg (also no scrambled egg) with the complementary food. The recommendation to introduce peanut in complementary feeding was formulated cautiously for the German-speaking countries: In families who usually consume peanut, the regular administration of peanut-containing foods in age-appropriate form (e.g., peanut butter) with the complementary diet can be considered for the primary prevention of peanut allergy in infants with atopic dermatitis (AD). Before introduction, a clinically relevant peanut allergy must be ruled out, especially in infants with moderate to severe AD. There is still insufficient evidence for an allergy-preventive efficacy of prebiotics or probiotics, vitamin D, or other vitamins in the form of supplements so that recommendations against their supplementation were adopted for the first time in the current guideline. Biodiversity plays an important role in the development of immunological tolerance to environmental and food allergens: there is clear evidence that growing up on a farm is associated with a lower risk of developing asthma and allergic diseases. This is associated with early non-specific immune stimulation due to, among other things, the greater microbial biodiversity of house dust in this habitat. This aspect is also reflected in the recommendations on animal husbandry, on which a differentiated statement was made: In families without a recognizable increased allergy risk, pet keeping with cats or dogs should not generally be restricted. Families with an increased allergy risk or with children with already existing AD should not acquire a new cat - in contrast, however, dog ownership should not be discouraged. Interventions to reduce exposure to dust mite allergens in the home, such as the use of mite allergen-proof mattress covers ("encasings"), should be restricted to patients with already proven specific sensitization against house dust mite allergen. Children born by caesarean section have a slightly increased risk of asthma - this should be taken into account when advising on mode of delivery outside of emergency situations. Recent work also supports the recommendations on air pollutants: Active and passive exposure to tobacco smoke increase the risk of allergies, especially asthma, and should therefore be avoided. Exposure to nitrogen oxides, ozone, and small particles (PM 2.5) is associated with an increased risk, especially for asthma. Therefore, exposure to emissions of nitrogen oxides, ozone, and small particles (PM 2.5) should be kept low. The authors of this guideline are unanimously in favor of enacting appropriate regulations to minimize these air pollutants. There is no evidence that vaccinations increase the risk of allergies, but conversely there is evidence that vaccinations can reduce the risk of allergies. All children, including children at risk, should be vaccinated according to the current recommendations of the national public health institutes, also for reasons of allergy prevention.

CONCLUSION

The consensus of recommendations in this guideline is based on an extensive evidence base. The update of the guideline enables evidence-based and up-to-date recommendations for the prevention of allergic diseases including asthma and atopic dermatitis.

The Role of Breastfeeding on Respiratory Outcomes Later in Childhood

BACKGROUND

Breastfeeding is associated with a lower risk of wheezing in early childhood, but its effect later in childhood remains unclear. We investigated the association of breastfeeding and respiratory outcomes in children aged 11 years.

MATERIALS AND METHODS

We performed an observational longitudinal study including 110 prepubertal children. Information about breastfeeding duration, wheezing and asthma was collected by questionnaires. At 11 years of age, we measured spirometry parameters, lung volumes, diffusing lung capacity, and fractional exhaled nitric oxide. We used logistic and linear regression models to examine the associations of breastfeeding duration with the odds of asthma and lung function measures. All multivariable analyses were adjusted for sex, smoking during pregnancy, gestational age at birth, twins, and mode of delivery (confounder model).

RESULTS

Breastfeeding duration was associated with FEV₁ z-score [β = 0.04, CI 95% (0.02-0.09)], FEF75 z-score [β = 0.06, CI 95% (0.03-0.09)] and FEV₁/FVC z-score [β = 0.03, CI 95% (0.00-0.07)], but not with diffusing lung capacity and fractional exhaled nitric oxide. No association of breastfeeding duration with preschool wheezing, ever asthma and current asthma was documented.

CONCLUSION

We showed that children breastfed for longer time presented higher FEV₁, FEV₁/FVC, and FEF75 z-score values at 11 years of age compared to children breastfed for shorter time, suggesting a protective effect of breastfeeding on airways, and not on lung parenchyma (lung volumes and alveolar capillary membrane) or allergic airway inflammation. The positive effect of breastfeeding duration on lung function lays the foundation to promote breastfeeding more and more as effective preventive measure.

Breastfeeding and wheeze-related outcomes in high-risk infants: A systematic review and meta-analysis

BACKGROUND

The risk of wheezing is high in infancy and is heightened in infants with a family history of asthma/atopy. The role of breastfeeding in influencing respiratory health for these high-risk infants is unclear.

OBJECTIVES

To systematically appraise evidence for the association between breastfeeding and wheeze incidences and severity in high-risk infants.

METHODS

Studies identified through electronic databases and reference lists were eligible if they assessed breastfeeding and respiratory outcomes in infants with a family history of asthma/atopy. The primary outcome was wheeze incidences in the first year of life. Secondary outcomes were wheeze incidences in the first 6 months of life, indicators of wheeze severity (recurrent wheeze, health-care utilization, and medication use), and other wheeze-related outcomes [bronchiolitis, pneumonia, croup, and incidence of lower respiratory tract infection (LRTI)] up to 12 months old. Meta-analyses were conducted where possible.

RESULTS

Of 1843 articles screened, 15 observational studies met the inclusion criteria. Breastfeeding was associated with 32% reduced odds of wheezing during the first year of life (ever vs. never: OR, 0.68; 95% CI: 0.53, 0.88; n = 9 studies); this association was even stronger in the first 6 months (OR, 0.45; 95% CI: 0.27, 0.75; n = 5 studies). Breastfeeding for a "longer" versus "shorter" time (approximately longer vs. shorter than 3 months) was associated with 50% reduced odds of wheezing at the age of 6 months (OR, 0.50; 95% CI: 0.39, 0.64; n = 3 studies).

CONCLUSIONS

Breastfeeding was associated with reduced odds of wheezing in high-risk infants, with the strongest protection in the first 6 months. More research is needed to understand the impact of breastfeeding intensity on wheezing and to examine additional respiratory outcomes, including wheeze severity. This review was registered at PROSPERO as CRD42019118631.

Duration of breastfeeding, age at introduction of complementary foods and allergy-related diseases: a prospective cohort study

Background

The influences of breastfeeding and infant diet in the prevention of allergy-related diseases are uncertain and many of the studies conducted on the topic are limited by methodological challenges. Our aim was to assess whether the duration of breastfeeding and age at complementary food introduction affected the prevalence of asthma, wheeze, allergic rhinoconjunctivitis (ARC) and eczema at two and six years of age.

Methods

We used information gathered between 2000 and 2014 through questionnaires in the Prevention of Allergy among Children in Trondheim (PACT) study, a prospective cohort study in Trondheim, Norway. The current study includes 6802 children who submitted questionnaires detailing breastfeeding duration and or age at introduction to complementary foods, as well as at least one of the child health questionnaires completed at two and six years of age. Adjusted odds ratios (aORs) were calculated for each combination of exposure and outcomes and sensitivity analyses were performed to assess the possible influence of recall bias and reverse causality.

Results

The mean duration of breastfeeding was 11 months (SD 5.6) in this study population and 5695 of 6796 (84%) infants had been breastfed for at least 6 months. We did not find any conclusive preventative effect of longer breastfeeding on parental reported doctor-diagnosed asthma, aOR 0.79 (95% CI 0.51, 1.21). However, at 6 years of age we observed a reduction in the less strictly defined outcome wheeze, aOR 0.71 (95% CI 0.53, 0.95). Longer breastfeeding was associated with a reduced risk of ARC at 2 years, aOR 0.65 (95% CI 0.49, 0.86), with a continued protective trend at 6 years, aOR 0.77 (95% CI 0.58, 1.04).

Conclusions

Longer breastfeeding resulted in a reduced risk of wheeze and a trend towards a protective effect on ARC up until school age. No conclusive associations were seen between the duration of breastfeeding or age at introduction to complementary foods and prevention of asthma, wheeze, ARC and eczema.

Trial registration

The trial is registered in Current Controlled Trials as ISRCTN28090297.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13006-020-00352-2.