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By Laurie Barclay, MD
CME Author: Penny Murata, MD
July 14, 2006 — Full breast-feeding reduces the rate of hospital admissions for infections in the infant by one half during the first year of life, according to the results of a study reported in the July issue of Pediatrics.
“Numerous studies have shown the benefits of breastfeeding for preventing morbidity from gastroenteritis and respiratory infections, and the effects on decreasing hospitalization rates, health expenditure, and mortality as a result of these infections,” write José María Paricio Talayero, MD, PhD, from the Hospital Marina Alta in Denia (Alicante), Spain, and colleagues. “Decision-making health authorities still are reluctant to define risk-benefit-based policies to promote breastfeeding that are suitable for an industrialized nation. The objective of this study was to assess the effect of breastfeeding on the probability of hospitalization as a result of infectious processes during the first year of life.”
Between 1996 and 1999, the investigators followed up 1385 infants from birth to age 1 year, using the 6-month well-infant visit under the National Child Health Program for recruitment and data collection concerning full breast-feeding, hospital admission, delivery, infant, mother, health services system, and sociologic aspects.
The percentage of mother-infant pairs who were still full breast-feeding was 85% at discharge after delivery, 52% at 3 months, 41% at 4 months, and 15% at 6 months of age. Of 78 hospital admissions for infections, 38 were for respiratory tract infections and 16 were for gastrointestinal tract infections. Mean age at admission was 4.1 months.
Estimates of attributable risk suggested that 30% of hospital admissions would have been avoided for each additional month of full breast-feeding. It would therefore appear that 100% full breast-feeding of 4-month-old infants would avoid 56% of hospital admissions in infants who are younger than 1 year. Other factors protecting against hospitalization were birth weight of 3 kg or more and no siblings.
Study limitations include residual detection bias; the possibility that the type of follow-up used could have hidden unsuspected biases; and only 2 of the children admitted were attending a child care center.
“On the basis of the present data, we conclude that full breastfeeding would lower the risk for hospital admission as a result of infections among infants who are younger than 1 year within an industrialized country,” the authors write.
“The results are consistent with early studies and add to the body of evidence confirming the hypothesis that full breastfeeding lowers the risk for hospitalization as a result of infectious diseases during the first year of life in a developed country.”
Medscape is citing this Full Text Article:
Full Breastfeeding and Hospitalization as a Result of Infections in the First Year of Life
PEDIATRICS 2006 (Jul); 118 (1): e92-e99
OBJECTIVE: Our objective was to assess the effect of breastfeeding on the probability of hospitalization as a result of infectious processes during the first year of life.
METHODS: We followed 1385 infants from birth to age 1 year between 1996 and 1999. Recruitment and data collection were done at the 6-month well-infant visit under the National Child Health Program. Full breastfeeding, hospital admission, and other relevant variables related to the delivery, infant, mother, health services system, and sociologic aspects were recorded. The statistical analysis included Kaplan-Meier test, Cox regression to obtain the hazard ratio, and the adjusted attributable risk.
RESULTS: Full breastfeeding at discharge after delivery and at 3, 4, and 6 months of age were 85%, 52%, 41%, and 15%, respectively; 78 hospital admissions as a result of infections were recorded (38 respiratory tract, 16 gastrointestinal tract). Mean age at admission was 4.1 months. After estimating the attributable risk, it was found that 30% of hospital admissions would have been avoided for each additional month of full breastfeeding. Seemingly, 100% of full breastfeeding among 4-month-old infants would avoid 56% of hospital admissions in infants who are younger than 1 year.
CONCLUSIONS: On the basis of the present data, we conclude that full breastfeeding would lower the risk for hospital admission as a result of infections among infants who are younger than 1 year within an industrialized country.
From the Full-Text Article:
After adjustment for the variables that could confound or change the effect of the relationship in this study, as well as previous studies, multivariate analysis showed a protective effect against hospitalization as a result of infection by 3 factors: FB, birth weight of 3 kg or more, and no siblings. The adjusted population attributable at risk, as a measure of epidemiologic impact, clearly demonstrates the importance of breastfeeding in the prevention of hospitalization for infection, a finding that is consistent with previously published series, in which lower birth weight (particularly <2500 g) increased the risk for death as a result of infections,  the frequency of pneumonia,  and the incidence of hospitalizations as a result of bronchiolitis.  For prevention of overestimation of the benefits of breastfeeding for preventing infection, birth weight always must be included as a variable in this kind of study because it is related to the frequency and the duration of lactation and, therefore, is a potential confounding factor. [50, 51] Having siblings also has been identified as a risk factor for infection by most series that analyze this relationship. [2, 11, 20, 22, 44]
In our study, the relationship between maternal smoking and hospitalization for infection that was observed in the univariate analysis was not found in the multivariate analysis, however. Several reports have shown that maternal and family smoking increases the frequency of respiratory tract infections and hospitalizations for this reason, [11, 42, 44, 52, 53] although the relationship is not entirely clear: some studies have not found an association, [15, 21, 54] another found it only in the univariate analysis,  and another found it in a multivariate analysis, in which relevant variables such as birth weight, gender, and presence of siblings were missing.  The economic level, unemployment rate, and distance to the hospital, described in other studies, [42, 56–58] were not shown to be predisposing factors for infection or hospitalizations for infection among infants in this study, perhaps because of a low variability of these parameters in our health area and because free universal access to medical care is available through a primary health care network. 
We found a protective effect of breastfeeding on hospitalization as a result of infections, consistent with other series [19, 22, 23, 41] as well as with a meta-analysis that was performed by Bachrach  of studies that were conducted in industrialized countries. Only 2 studies in industrialized nations report no breastfeeding protection against hospitalizations as a result of infection, whether caused by gastroenteritis  or infections in general.  In another study, Chen et al  showed breastfeeding protection against hospitalizations that were caused by nongastrointestinal infections but did not report the same effect for hospitalizations for gastroenteritis, perhaps because of a lengthy follow-up of 18 months of life, late data collection (questionnaire at 18 months, possibly encouraging a memory bias), and the contrast between formula-feeding and any type of breastfeeding, without using the WHO definitions.
Kramer et al,  in a study that compared 2 large cohorts from different regions of Belarus, found that breastfeeding provided protection during the first year of life against gastroenteritis but not respiratory infections or otitis and not for hospitalizations as a result of infection. This study performed an ecological assignment of the main explanatory variable, percentage breastfeeding of population, although the spatial and cultural distances, probably large, between the 2 cohorts did not seem to have been reflected in the statistical adjustment.
One limitation of our study could be that the detection bias was not completely eliminated: the knowledge that we obtained regarding the protective role of breastfeeding or the differing confidence (breastfed infants are less likely to be admitted) that we had in the mother's caregiver skills according to type of lactation could influence hospitalization. Nevertheless, the protection may have been underestimated, because it is observed despite the low level of hospitalization found. Although the type of follow-up used could have hidden unsuspected biases, the distribution of the cohort was consistent with those observed in the 2 other files that were available to us: 1 for hospitalized patients and another for infants who were born in the hospital.
Child care attendance is a known factor for higher risk for infections in the early years of childhood,41,60,61 although it does not always appear  or appears in association with poverty conditions.  This variable was not controlled in this study because only 2 of the children admitted were attending a child care center.
For prevention of most of the supposed methodologic problems of lactation studies,  all potential confounding and interaction variables that were mentioned in the literature were controlled and statistical methods that were considered appropriate for survival time analysis were used. In addition, the WHO criteria were followed for the main independent variable (FB), the outcome measure was defined precisely, and the dose-response effect was measured by introducing FB time as a continuous variable (expressed in months), making it possible to determine of risk ratio of hospitalization that was attributable to infection per unit time of FB. Finally, the independence of lactation time was checked with respect to hospitalization as a result of an infectious cause because the hospitalization did not affect the duration of breastfeeding. Possible memory biases were avoided by careful collection of data on the main variables. Advanced techniques for survival studies were used in the statistical analysis, in particular, Cox regression, a method first used by Arifeen et al  to analyze the ratio between breastfeeding and mortality from respiratory and gastrointestinal infections.
This study is the first that was conducted in Spain and 1 of the few conducted in industrialized nations to study the relationship between breastfeeding and hospitalization as a result of infection among an extensive cohort (1385 children) using multivariate Cox regression. The results are consistent with early studies and add to the body of evidence confirming the hypothesis that FB lowers the risk for hospitalization as a result of infectious diseases during the first year of life in a developed country.
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