Longer duration of exclusive breastfeeding appears protective against childhood asthma

Infants who exclusively breastfed for longer durations experienced lower odds for developing asthma compared with other infants, according to a study published in Annals of Allergy, Asthma & Immunology.

These results extend the 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 Science Center in Memphis, and colleagues wrote.

The researchers examined data from 2,021 maternal-child 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. Also, 44% reported an education level of high school or less. There were few women who smoked during pregnancy as well (range among the cohorts, 3%-9%).

The population of children was 50% female, with 42% classified as first-born children and 34% born via cesarean delivery. At birth, the median gestational age was 39.29 weeks (interquartile range [IQR], 38.43-40.14 weeks).

Questionnaires conducted when the children were aged 4 to 6 years (IQR, 4.1-4.5 years) asked mothers about durations of any and exclusive breastfeeding.

Also, the International Study of Asthma and Allergies in Childhood and other questionnaires assessed child wheeze and asthma outcomes as well as asthma-specific medication use and diagnosis, leading the researchers to consider current wheeze, ever asthma, current asthma and strict current asthma in their outcomes.

Overall, 16% of the children had current wheeze, 12% had ever asthma, 12% had current asthma and 9% had strict current asthma.

Among the children, 33% were never breastfed or breastfed for less than 2 months, 13% were breastfed for 2 to 4 months, 9% were breastfed for 5 to 6 months and 45% were breastfed for more than 6 months.

Also, 68% of the women who breastfed their child for more than 6 months were white, and 78% had more than a high school education.

The researchers did not find any association between the duration of breastfeeding and child wheeze or asthma outcomes. Although there was no statistical significance in the overall adjusted association for ever asthma, the researchers found a significant linear trend toward protection (P = .034).

Researchers observed decreased odds for ever asthma among children breastfed for 2 to 4 months (adjusted OR = 0.79; 95% CI, 0.49-1.24), 5 to 6 months (aOR = 0.72; 95% CI, 0.42-1.25) and longer than 6 months (aOR = 0.65; 95% CI, 0.43-0.97) compared with children breastfed for less than 2 months.

Also, there was an association between longer duration of exclusive breastfeeding and decreased odds for current asthma for 2 to 4 months (aOR = 0.64; 95% CI, 0.41-1.02), 5 to 6 months (aOR = 0.61; 95% CI, 0.38-0.98) and longer than 6 months (aOR = 0.52; 95% CI, 0.31-0.87) of exclusive breastfeeding compared with less than 2 months.

The researchers further found protective associations for current wheeze, ever asthma and strict current asthma with more than 6 months of exclusive breastfeeding compared with less than 2 months of exclusive breastfeeding and with never to less than 2 months of any breastfeeding.

Researchers also reported linear trends with longer duration of exclusive breastfeeding and current wheeze, ever asthma (P = .005), current asthma (P = .009) and strict current asthma (P = .018).

Additionally, the researchers found no statistically significant interactions between mode of delivery and duration of any breastfeeding on child wheeze or asthma outcomes.

However, dyads with vaginal deliveries had consistently stronger protective associations for child wheeze and asthma outcomes based on breastfeeding duration, compared with cesarean deliveries, although the differences did not reach statistical significance.

Also, the protective effect of longer breastfeeding duration appeared restricted to mothers who did not have asthma, with an adjusted OR of 0.58 (95% CI, 0.37-0.92) for breastfeeding longer than 6 months vs. less than 2 months, but not among the children of mothers with asthma (aOR = 1.49; 95% CI, 0.79-2.8).

The researchers called their findings evidence of protective associations between exclusive breastfeeding continued for longer durations and child asthma outcomes, although when considering the duration of any breastfeeding, there was no strong association between subsequent development of wheeze or asthma apart from ever asthma.