Original Article
Breastfeeding Protects against Current Asthma up to 6 Years of Age

https://doi.org/10.1016/j.jpeds.2011.11.055Get rights and content

Objective

To investigate the effects of breastfeeding on wheezing and current asthma in children 2 to 6 years of age.

Study design

Infants (n = 1105) were enrolled in a prospective birth cohort in New Zealand. Detailed information about infant feeding was collected using questionnaires administered at birth and at 3, 6, and 15 months. From this, durations of exclusive and any breastfeeding were calculated. Information about wheezing and current asthma was collected at 2, 3, 4, 5, and 6 years. Logistic regression was used to model associations between breastfeeding and outcomes with and without adjustment for confounders.

Results

After adjustment for confounders, each month of exclusive breastfeeding was associated with significant reductions in current asthma from 2 to 6 years (all, P < .03). Current asthma at 2, 3, and 4 years was also reduced by each month of any breastfeeding (all, P < .005). In atopic children, exclusive breastfeeding for ≥3 months reduced current asthma at ages 4, 5, and 6 by 62%, 55%, and 59%, respectively.

Conclusion

Breastfeeding, particularly exclusive breastfeeding, protects against current asthma up to 6 years. Although exclusive breastfeeding reduced risk of current asthma in all children to age 6, the degree of protection beyond 3 years was more pronounced in atopic children.

Section snippets

Methods

The New Zealand Asthma and Allergy Cohort Study was established in Christchurch and Wellington in 1997 as a large prospective birth cohort to investigate risk factors for the development of asthma. Ethics approval for the study was obtained from the Wellington and Canterbury Regional Ethics Committees. Full details of the cohort, including assembly, demographics, and methodology, have been published elsewhere.13

Recruitment took place in Christchurch and Wellington between 1997 and 2001.

Results

A total of 1105 children were enrolled before birth. Questionnaires were completed for 1064 children at 3 months (96.3%), 1011 at 15 months (91.5%), 1011 at 2 years (91.5%), 1007 at 3 years (91.1%), 986 at 4 years (89.2%), 990 at 5 years (89.6%), and 920 (83.3%) at 6 years, with complete data available to 6 years for 892 (80.7%) children. Key characteristics and the prevalence of outcomes of those for whom there were complete breastfeeding data are listed in Table I.

Discussion

Our results show that breastfeeding, particularly exclusive breastfeeding, continued to protect against current asthma from 2 to 6 years of age. Although the degree of protection for each month of exclusive breastfeeding across the whole cohort decreased from 21% at 15 months3 to around 9% at 6 years, it is important to stress the magnitude of these findings. For instance, if every infant in this cohort had been exclusively breast fed for 6 months, as is currently recommended by the World

References (17)

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    Given that breastfeeding likely protects against RTIs,37 a reduction in RTI-induced wheeze due to breastfeeding may mistakenly be misclassified as a reduction in asthma, thereby overestimating a protective association between breastfeeding and asthma. This potentially explains findings from longitudinal studies that showed a significant protective effect of breastfeeding on asthma in early childhood that attenuated as the child aged.7,8 Given that The International Consensus on Paediatric Asthma highlights age 5 years as a turning point for the reliability of an asthma diagnosis38 and our study used a relatively specific definition of doctor-diagnosed asthma, our study is less likely to be subject to such misclassification.

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Funded by grants from the Health Research Council of New Zealand, the Child Health Research Foundation, the Canterbury Medical Research Foundation, the Asthma Research Foundation of New Zealand (Christchurch), and the David and Cassie Anderson Bequest (Wellington). The authors declare no conflicts of interest.

List of members of the New Zealand Asthma and Allergy Cohort Study Group is available at www.jpeds.com (Appendix).

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