Breastfeeding may substantially reduce the risk of sudden infant death syndrome (SIDS), especially when breast milk is the sole nutritional source, a meta-analysis showed.
Any breastfeeding was associated with an independent 45% reduction in risk of SIDS, Fern R. Hauck, MD, MS, of the University of Virginia School of Medicine in Charlottesville, and colleagues reported in the July issue of Pediatrics
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Breastfeeding as the sole source of nutrition for any duration was associated with a 73% reduction in SIDS (summary odds ratio 0.27, 95% confidence interval 0.24 to 0.31).
This advantage adds to the many infant and maternal benefits of breastfeeding, the researchers noted.
"The recommendation to breastfeed infants should be included with other SIDS risk-reduction messages," the researchers recommended in the paper.
"Ideally, breastfeeding should be exclusive (ie, formula should not be given) for at least four to six months and should be continued until the infant is at least 1 year of age," Hauck's group suggested in concordance with American Academy of Pediatrics' guidelines for six months of exclusive breastfeeding and continuation through age 1 year.
Other factors linked in epidemiologic studies to lower risk of SIDS, such as pacifier use and keeping the baby in the same room but not the same bed as the mother, do not necessarily run counter to promoting breastfeeding, they noted.
The authors pointed out that previous research has found an association between bed-sharing and increased breastfeeding duration. But it is not clear whether bed-sharing increases breastfeeding or if parents who breastfeed subsequently decide to bed-share, Hauck and colleagues said.
And pacifier use after breastfeeding has been deemed acceptable as long as breastfeeding has been well established, according to AAP policy statements.
The meta-analysis included 18 case-control studies on breastfeeding and SIDS risk.
Altogether, breastfeeding of any duration or level of exclusivity was associated with a 60% reduction in SIDS risk (univariate summary odds ratio 0.40, 95% CI 0.35 to 0.44).
The seven studies that provided multivariate adjusted results showed a similar 0.36 univariate odds ratio (95% CI 0.31 to 0.42) that was attenuated somewhat to 0.55 with multivariate adjustment though still significant (95% CI 0.44 to 0.69).
This result suggested that "breastfeeding itself is protective and not merely a marker of other potentially protective factors, such as the absence of smoke exposure or sociodemographic factors," the researchers wrote in Pediatrics.
The three studies that reported on any breastfeeding at 2 months of age or older came in at a univariate odds ratio of 0.38 (95% CI 0.27 to 0.54).
A sensitivity analysis that included five studies not included in the meta-analysis for failing to meet quality criteria suggested a less dramatic benefit for SIDS risk reduction with breastfeeding (univariate OR 0.49, multivariate OR 0.68) but one that remained statistically significant.
These observational study-based findings could not establish causality, but there are factors supporting causality of breastfeeding in preventing SIDS, according to Hauck's group.
These factors include consistent findings, strong associations, a dose-response effect, and the fact that breastfeeding or not precedes SIDS, as well as biological plausibility.
Biological plausibility stems from breastfed infants being more easily aroused from sleep compared with bottle-fed babies during the peak period of SIDS risk from 2 to 4 months of age. Breastfeeding also confers better immunity against minor infections often seen in the days before SIDS death, the group noted.
The investigators did caution, though, that they could not rule out reverse causality or bias from inadequate recall of breastfeeding duration.
Source reference:
Hauck FR, et al "Breastfeeding and reduced risk of sudden infant death syndrome: A meta-analysis" Pediatrics 2011; DOI: 10.1542/peds.2010-3000.
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