Bauchner H, Leventhal J M, Shapiro E D
JAMA. 1986 Aug 15;256(7):887-92.
We assessed the extent to which studies of the association between breast-feeding and infection met four important methodological standards that relate to both the scientific validity and the generalizability of the studies. Of the 20 studies (14 cohort, six case-control), only six met three or four of the methodological standards. Four of these six studies found that breast-feeding was not protective against infections and two found that breast-feeding was protective against infections. In the three studies in which statistical adjustments were made for three additional potentially important confounding variables--size of the family, smoking of cigarettes by the mother, and the mother's level of education-the apparent protective effect of breast-feeding against respiratory tract infections disappeared after the adjustments were made. We found that most of the studies have major methodological flaws that may have compromised their conclusions. The studies that met important methodological standards and controlled for confounding variables suggest that breast-feeding has at most a minimal protective effect in industrialized countries.
我们评估了关于母乳喂养与感染之间关联的研究在多大程度上符合与研究的科学有效性和普遍性相关的四项重要方法学标准。在这20项研究中（14项队列研究，6项病例对照研究），只有6项符合三项或四项方法学标准。这六项研究中有四项发现母乳喂养对感染没有保护作用，两项发现母乳喂养对感染有保护作用。在三项针对另外三个潜在重要混杂变量进行统计调整的研究中——家庭规模、母亲吸烟情况以及母亲的教育水平——调整后母乳喂养对呼吸道感染的明显保护作用消失了。我们发现大多数研究存在重大方法学缺陷，这可能影响了它们的结论。符合重要方法学标准并控制了混杂变量的研究表明，在工业化国家，母乳喂养至多具有极小的保护作用。
