Breast Milk and the Prevention of Infections By Dr. M.T. Ste-Marie In spite of accumulating evidence, some North American health care professionals tend to believe that beyond preventing gastrointestinal infections, breast milk does not have any significant benefits for infants from well-developed countries. Prevention of lower respiratory tract infections including pneumonia, respiratory syncytial virus, bronchiolitis, otitis media, bacteremia and meningitis as well as a significant decrease in hospital admissions have been considered as "developing countries benefits" 1. Until recently, few studies have focused on infant cohorts from industrialized countries 2,3with somewhat mixed results. In order to detect significant differences in these populations, it was postulated that very large groups of infants had to be studied on a prospective basis. The opportunity presented itself when a study of infant feeding in New Brunswick was undertaken to provide information for the development of an infant nutrition program 4. Subjects were drawn from cluster samples of all normal term infants born to primipara women over a two year period. Mothers were contacted by mail and if they agreed to participate, filled in a detailed questionnaire when their infant reached six months of age. Breast-feeding infants included those who were exclusively breast-fed and those whose breast-feeding was complemented with another liquid intake such as water and/ or solid foods. Those infants who were still breast-fed at six months of age were considered to have been breast-fed for the entire period. Bottle feeding infants were those who had used an infant formula or cow’s milk from birth. The questionnaire included data at every week since birth up to six months; infants were classified every week into either group depending on their feeding pattern. Gastrointestinal and respiratory illness were studied as different categories and all other illnesses were included in a third category. Illnesses of less than three days were disregarded; the duration of each illness was noted as well as the age of the baby at the time. Admissions to hospital were recorded. Symptoms were classified according to whether they represented a true gastrointestinal illness or an episode of respiratory illness such as cold, influenza, pneumonia, chest cold, etc. For the purposes of this study otitis was included with respiratory illnesses. Other variables considered in the data analysis included the age, birth weight, month of birth, and daycare situation of the infants, the age, cigarette consumption of the mothers and their socio-economic status based upon education and occupation. The rates of illnesses were calculated as the total number of episodes of a particular illness over the aggregate number of weeks of breast-feeding or bottle feeding. This represented an incidence density. The incidence density ratio (IDR) was then calculated; this corresponded to the rate of one specific illness among breast-fed infants divided by the rate of the same type of illness among bottle-fed infants. When equal to one, the incidence ratio indicated no association between breast-feeding and the rate of illness, and when less than one, a protective effect of breast-feeding. During the two year period, there were approximately 1,400 eligible mothers. Sixty-two percent agreed to participate, and of those who agreed to participate, ninety percent returned a valid questionnaire. The infants breast-fed at birth came from a higher socioeconomic status group and had older mothers than those who were fed infant formulas. On the other hand, infants from the bottle-fed group had mothers who smoked more cigarettes. There was no difference in birth weight or in the number of children sharing daycare facilities with the child under study. The incidence of exclusive breast-feeding was extremely low after the first few weeks. Only thirteen percent of infants were exclusively breast-fed at three months and one percent at six months. Of the fifty-six percent of infants who were exclusively or partially breast-fed at birth, thirty one percent remained at three months, and sixteen percent at six months (table 1). Half of the babies had had some juice or solids before the age of three months, (sixty-five percent among those never breast-fed and twenty-five percent among those breast-fed for fourteen weeks or more). Five hundred and thirty episodes of illness were observed in the 776 infants studied; forty-seven percent had at least one episode of illness. Respiratory illnesses were by far the most frequent, accounting for eighty percent of the episodes. Within those, thirteen percent were classified as ear infections. There was a significant protective effect of breast-feeding against all illnesses during the first six months of life. The incidence density for gastrointestinal illnesses was forty percent lower in breast-fed infants, and for respiratory illness, thirty percent lower. Even when the data were corrected for confounding variables related to the infant (age, birthweight, month of birth, day care situation) and to the mother (age, cigarette consumption and socio-economic status), the incidence density ratio did not change. When otitis media was separated from the rest of the respiratory illnesses, the protective effect of breast-feeding remained in both categories. Children were sampled from four clusters occurring at different times of the year; there was no difference noted between the incidence of breast milk protection due to change of season. Finally, only one hospitalization occurred for one episode of respiratory illness during breast-feeding weeks compared with fifty-one during bottle feeding weeks. These results confirm those of a number of previous studies 2,5. Although the data were based upon a single, retrospective, mailed-in questionnaire, it is well known that first time mothers have an excellent memory concerning their baby’s health. If the study had been prospective, the quality of reporting might have been even more complete and precise. The authors concluded that breast-feeding is protective against respiratory illness including ear infection, and gastrointestinal problems. It also significantly decreased hospitalizations for respiratory illness. A recently published prospective study from the University of California did not show any significant difference in the rate of respiratory illnesses between breast-fed and formula fed infants. However in the first year of life, the incidence of diarrhea was fifty percent less among breast-fed infants and otitis media twenty percent less. These infant cohorts were well matched. 6Some groups have postulated that positioning the baby during feeding is responsible for the noticed decrease in ear infections in breast-fed babies. To that effect, a few groups have advocated the semi upright position of the infant during any type of feeding in order to decrease the incidence of ear infections 7,8. Although this may play a role in preventing entry of milk into the middle ear, and reduce choking and regurgitation, it does not seem to play any evident role in the prevention of bacteremia, meningitis, lower respiratory tract infections or urinary tract infections 8,9. There are many reasons why conflicting results may be found in studies such as these. Obviously, randomized clinical trials are impossible and the observational approach used is subject to bias and errors due to confounding variables. A number of confounding variables were considered in the New Brunswick study The influence of family size was eliminated by choosing first time mothers. The ethnicity of the group was also relatively homogeneous. Recall bias is probably the study’s most significant bias. The role of breast milk for the prevention of infections in non-developing countries may never be resolved to everyone’s satisfaction. However, despite potential problems associated with data collection, the New Brunswick study shows a firm trend in confirming the benefits of feeding infants during the first six months of life . This should help reinforce health care professionals advice to mothers that breast is best. References: 1. Cunningham AS, Jelliffe DB, Jelliffe EFP. Breast-feeding and health in the 1980’s: A global epidemiologic review. J Pediatr, 1991;118(5):659-65. 2. Howie PW, Forsyth JS, Ogston SA, Clark A, du V Florey C. Protective effect of breast-feeding against infection. BMJ, 1990,;300(6716):11-6. 3. Ford K, Labbok M. Breast-feeding and child health in the United States. J Biosoc Sci, 1993; 25:187-94. 4. Beaudry M, Dufour R, Marcoux S. Relation between infant feeding and infections during the first six months of life. J Pediatr, 1995;126:191-7. 5. Lawrence R. The clinician’s role in teaching proper infant feeding techniques. J Pediatr,1995;126(6):S112- 6. Dewey KG, Heinig J, Nommsen-Rivers LA. Differences in morbidity between breast-fed and formula-fed infants. J Pediatr. 1995; 126:696-702. 7. Tully SB, Bar-Haim Y, Bradley RL. Abnormal typanography after supine bottle feeding. J Pediatr, 1995;126(6):S105-11. 8. Coppa GV, Gabrielli O, Giorgio P, Catassi C, Montanari MP, Varoldo PE, Nichols BL. Preliminary study of breast-feeding and bacterial adhesion to uroepithelial cells. Lancet, 1990;335(8689):569-71. 9. Pisacane A.;Graziano L.; Zona G. Breastfeeding and urinary tract infection. Lancet 1990 Jul 7;336 (8706):50. Table1 Incidence of Breast-feeding and Formula feeding among infants under study
|
