BACKGROUND:The protection of breastfeeding against respiratory tract infections in the first year of life has often been suggested. Few studies examined the effect of breastfeeding on respiratory tract infections after infancy.

OBJECTIVE:To examine the association between breastfeeding with lower respiratory tract infections (LRTI) and upper respiratory tract infections (URTI) after infancy up to 4 years of age (n = 5322).

METHODS:This study was embedded in The Generation R study, a Dutch population-based prospective cohort study from fetal life until young adulthood. Information on breastfeeding duration (never;<3 months; 3-6 months;≥6 months) and dose (never; partially until 4 months; predominantly until 4 months) were collected by questionnaire at 2, 6, and 12 months of age. Information on doctor attendance for LRTI and URTI were obtained by questionnaire at 2, 3, and 4 years of age.

RESULTS:Breastfeeding for 6 months or longer was significantly associated with a reduced risk of LRTI up to 4 years of age (aOR: 0.71; 95% CI: 0.51-0.98). Similar ORs for LRTI were found with breastfeeding for less than 3 months and 3-6 months. Although in the same direction, weaker ORs were found for URTI and breastfeeding duration. The same trend was found for partial and predominant breastfeeding until 4 months and LRTI and URTI.

CONCLUSION:Breastfeeding duration for 6 months or longer is associated with a reduced risk of LRTI in pre-school children. These findings are compatible with the hypothesis that the protective effect of breastfeeding for respiratory tract infections persist after infancy therefore supporting current recommendations for breastfeeding for at least 6 months.

Most infants in the UK start solids before the recommended age of 6 months. We assessed the independent effects of solids and breast feeding on the risk of hospitalisation for infection in term, singleton infants in the Millennium Cohort Study (n = 15,980). For both diarrhoea and lower respiratory tract infection (LRTI), the monthly risk of hospitalisation was significantly lower in those receiving breast milk compared with those receiving formula. The monthly risk of hospitalisation was not significantly higher in those who had received solids compared with those not on solids (for diarrhoea, adjusted odds ratio 1.39, 95% CI 0.75 to 2.59; for LRTI, adjusted odds ratio 1.14, 95% CI 0.76 to 1.70), and the risk did not vary significantly according to the age of starting solids.