Duration of breastfeeding and age of introduction to complementary foods were not found to be correlated with the presence of asthma at 7 years of age according to the results of a large prospective Norwegian cohort study published in The Journal of Pediatrics.
Anne Kristine Lossius, MD, of the Pediatric Department, Ostfold Hospital Trust, Gralum, Norway, and colleagues analyzed data from the Norwegian Mother and Child Study, a nationwide prospective cohort study that recruited pregnant women from across Norway between 1999 and 2008. Children with complete breastfeeding data up to 18 months were eligible for inclusion in the study.
The primary outcome, asthma development, was defined based on 2 or more dispensed asthma medications at 7 years of age registered in the Norwegian Prescription Database. The authors used log-binomial regression models to obtain crude relative risks (RRs) in the main analysis, and then adjusted for selected confounders in multivariable analyses.
Of the 41,020 eligible participants, 79% were still breastfed at 6 months of age and 38% at 12 months of age or older. Of those infants who were still breastfed at 6 months, 78% had been introduced to solid foods and 36% were supplemented with formula before 6 months of age.
In this cohort, 5.9% of infants breastfed for less than 6 months (adjusted RR [aRR] 1.05) and 4.6% who were breastfed for 6 to 11 months (aRR 0.96) were noted to have dispensed asthma medications at age 7 years compared with 4.6% of infants breastfed for more than 12 months (Ptrend .62).
Infants still breastfed at 6 months, but introduced to complementary foods earlier than 4 months and at 4 to 6 months, had an aRR of 1.15 and 1.09, respectively, compared with infants fully breastfed for 6 months (Ptrend .09). Ages at introduction of solids or formula separately were not significant predictors (Ptrend .16 and .08, respectively).
The authors concluded that no association was found between duration of any breastfeeding and asthma development at 7 years of age in this cohort of children.
The authors noted, however, that the risk for asthma was significantly increased for children breastfed less than 6 months compared with 12 months or longer.
Lossius AK, Magnus MC, Lunde J, Størdal K. Prospective cohort study of breastfeeding and the risk of childhood asthma [published online January 31, 2018]. J Pediatr. doi:10.1016/jpeds.2017.11.065