Objective: To examine breastfeeding and the risk of hospitalization for lower respiratory tract disease in healthy full-term infants with access to modern medical care.
Data sources: MEDLINE, personal communication with researchers, the OVID databases, Dissertation Abstracts Online, and BIOSIS.
Study selection: The titles, abstracts, and text of studies from developed countries were explored for breastfeeding exposure measures and lower respiratory tract disease hospitalization rates. For summary statistics, we required 3 inclusion criteria: (1) a feeding contrast of a minimum of 2 months of exclusive breastfeeding (no formula supplementation) vs no breastfeeding and (2) study populations that excluded sick, low birth weight or premature infants and (3) reflected affluent regions; 27% of studies met these criteria.
Data extraction: We abstracted data from all relevant reports.
Data synthesis: Data from all primary material (33 studies) indicated a protective association between breastfeeding and the risk of respiratory disease hospitalization. Nine studies met all inclusion criteria, and 7 cohort studies were pooled. The feeding contrasts in these 7 studies were 4 or more months of exclusive breastfeeding vs no breastfeeding. The summary relative risk (95% confidence interval) was 0.28 (0.14-0.54), using a random-effects model. This effect remained stable and statistically significant after adjusting for the effects of smoking or socioeconomic status.
Conclusion: Among generally healthy infants in developed nations, more than a tripling in severe respiratory tract illnesses resulting in hospitalizations was noted for infants who were not breastfed compared with those who were exclusively breastfed for 4 months.