According to a study published in Annals of Allergy, Asthma and Immunology.
These findings expand understanding of the association between breastfeeding and respiratory health, Keadrea Wilson, MD, pediatrician in the Division of Neonatology, Department of Pediatrics, at the University of Tennessee Health Sciences Center at Memphis, and colleagues wrote.
The researchers examined data from 2,021 mother-infant dyads enrolled in the NIH ECHO-PATHWAYS consortium drawn from three prospective pregnancy cohorts.
Within the maternal population, 38% of women identified as black, 52% as white, and 6% as Hispanic/Latina. In addition, 44% said they had a high school education or less. There were also few women who smoked during pregnancy (range among cohorts, 3% to 9%).
The child population was 50% female, with 42% classified as firstborn and 34% born by Caesarean section. At birth, the median gestational age was 39.29 weeks (interquartile range [IQR]38.43-40.14 weeks).
Questionnaires conducted when children were 4-6 years old (IQR, 4.1-4.5 years) asked mothers about the duration of possible and exclusive breastfeeding.
In addition, the International Childhood Asthma and Allergy Study and other questionnaires assessed childhood wheezing and asthma outcomes as well as medication use and diagnosis. specific to asthma, which led the researchers to consider current wheeze, past asthma, current asthma, and current strict asthma in their results.
Overall, 16% of the children had current wheeze, 12% had ever had asthma, 12% had current asthma, and 9% had current strict asthma.
Of the children, 33% were never breastfed or breastfed for less than 2 months, 13% were breastfed for 2-4 months, 9% were breastfed for 5-6 months, and 45% were breastfed for more than 6 month.
Additionally, 68% of women who breastfed for more than 6 months were white and 78% had more than a high school diploma.
The researchers found no association between breastfeeding duration and child wheeze or asthma outcomes. Although there was no statistical significance in the overall adjusted association for asthma, the researchers found a significant linear trend toward protection (P = 0.034).
The researchers observed a reduced risk of ever having asthma in children breastfed for 2 to 4 months (adjusted OR = 0.79; 95% CI, 0.49-1.24), 5 to 6 months (ORa = 0.72; 95% CI, 0.42-1.25) and longer than 6 months (aOR = 0.65; 95% CI, 0.43-0.97) compared to children breastfed for less of 2 months.
Additionally, there was an association between longer duration of exclusive breastfeeding and a decreased risk of current asthma for 2–4 months (aOR=0.64; 95% CI, 0.41-1, 02), 5-6 months (aOR=0.61; 95% CI, 0.38-0.98) and more than 6 months (aOR=0.52; 95% CI, 0.31-0, 87) exclusive breastfeeding compared to less than 2 months.
Researchers further found protective associations for current wheezing, asthma, and current strict asthma with more than 6 months of exclusive breastfeeding versus less than 2 months of exclusive breastfeeding and with never less than 2 months breastfeeding.
The researchers also reported linear trends with longer duration of exclusive breastfeeding and current wheezing or even asthma (P = 0.005), current asthma (P = 0.009) and current strict asthma (P = 0.018).
Additionally, the researchers found no statistically significant interaction between mode of delivery and duration of breastfeeding on child wheeze or asthma outcomes.
However, dyads with vaginal deliveries had consistently stronger protective associations for childhood wheeze and asthma outcomes as a function of breastfeeding duration, compared with cesarean deliveries, although the differences did not reach statistical significance.
Additionally, the protective effect of longer breastfeeding duration appeared to be limited to mothers who did not have asthma, with an adjusted OR of 0.58 (95% CI, 0.37-0.92) for breastfeeding more than 6 months versus less than 2 months, but not among children of asthmatic mothers (aOR = 1.49; 95% CI, 0.79-2.8).
The researchers called their findings evidence of protective associations between continued exclusive breastfeeding for longer durations and childhood asthma outcomes, although given the duration of any breastfeeding, it was no strong association between later development of wheeze or asthma apart from asthma.