What is the question?

• The question is: What is the relationship between shorter versus longer durations of any human milk feeding and inflammatory bowel disease?

What is the answer to the question?

• Limited but consistent evidence from case-control studies suggests that, among infants fed human milk, a shorter versus longer duration of any human milk feeding is associated with higher risk of inflammatory bowel disease. 

Why was this question asked? 

• This important public health question was identified and prioritized as part of the U.S. Department of Agriculture and Department of Health and Human Services Pregnancy and Birth to 24 Months Project.

How was this question answered? 

• A team of Nutrition Evidence Systematic Review staff conducted a systematic review in collaboration with a group of experts called a Technical Expert Collaborative.

What is the population of interest? 

• The population of interest was generally healthy infants and toddlers (ages 0-24 months) who were in studies examining inflammatory bowel disease throughout the lifespan.

What evidence was found? 

• This review includes 9 articles. 
• These articles compared infants fed human milk for shorter durations with infants fed human milk for longer durations. The infants could be fed any amount of human milk.
• These articles examined diagnosed inflammatory bowel disease, including Crohn’s disease and ulcerative colitis. 
• Individuals who were fed human milk for shorter durations may have higher risk of inflammatory bowel disease than individuals who were fed human milk for longer durations.
• There are limitations in the evidence as follows: 
  • There were not a lot of articles, and some of the articles studied groups of people that may have been too small to detect whether there is a relationship between shorter versus longer durations of any human milk feeding and inflammatory bowel disease.  
  • Most of the studies asked participants (who were generally adolescents or adults) and their parents to remember how long participants were fed human milk when they were infants, and if those with inflammatory bowel disease remembered or reported differently those without inflammatory bowel disease, it could impact the findings.

How up-to-date is this systematic review? 

• This review includes literature from 01/1980 to 03/2016.

 Background

• This systematic review was conducted as part of the U.S. Department of Agriculture and Department of Health and Human Services Pregnancy and Birth to 24 Months Project.
• The goal of this systematic review was to examine the following question: What is the relationship between shorter versus longer durations of any human milk feeding and inflammatory bowel disease?
• This systematic review examines comparisons of infants who were fed human milk for shorter durations with infants who were fed human milk for longer durations. Human milk feeding was defined as feeding human milk alone or in combination with infant formula and/or complementary foods or beverages such as cow’s milk.  Human milk was defined as mother’s own milk provided at the breast (i.e., nursing) or expressed and fed fresh or after refrigeration or freezing.  Donor milk (e.g., banked milk) was not examined in this review.  
• This systematic review examines diagnosed inflammatory bowel disease (including Crohn’s disease and ulcerative colitis), only, to ensure that it addresses the relationship of shorter versus longer durations of any human milk feeding with inflammatory bowel disease and not the relationship of shorter versus longer durations of any human milk feeding with the many other diseases and conditions with similar symptoms.

Conclusion Statement and Grade

• Limited but consistent evidence from case-control studies suggests that, among infants fed human milk, a shorter versus longer duration of any human milk feeding is associated with higher risk of inflammatory bowel disease. 
  
  Grade: Limited

Methods 

• The systematic review was conducted by a team of staff from the Nutrition Evidence Systematic Review in collaboration with a Technical Expert Collaborative.
• A single literature search was conducted to identify literature for several related systematic reviews that examined infant milk-feeding practices and different outcomes. The search was conducted in CINAHL, Cochrane, Embase, and PubMed, and used a search date range of January 1980 to March 2016. A manual search was done to identify articles that may not have been included in the electronic databases searched. 
• Articles were screened independently by 2 NESR analysts to determine which articles met predetermined criteria for inclusion.
• Data from each included article were extracted, risks of bias were assessed, and both were checked for accuracy. 
• The body of evidence was qualitatively synthesized, a conclusion statement was developed, and the strength of the evidence (grade) was assessed using pre-established criteria including evaluation of the internal validity/risk of bias, adequacy, consistency, impact, and generalizability of available evidence.

Summary of Evidence 

• Nine articles met the inclusion criteria, which presented evidence from 8 independent case-control studies because 1 research group examined Crohn’s disease and ulcerative colitis in the same population in separate articles. 
• The notable feature of this body of evidence is its consistency in the direction of the associations. Four of the 8 studies reported statistically significant inverse associations between the duration of any human milk feeding and inflammatory bowel disease outcomes, and a fifth study had confidence intervals in which the upper limit was at the null. Further, all of the studies that reported point estimates (i.e., significant and non-significant) had associations that were consistent in direction and, in some cases, the nonsignificant associations had wide confidence intervals indicative of suboptimal statistical power.  
• The ability to draw stronger conclusions was primarily limited by the small number of studies, insufficient sample sizes, the retrospective collection of exposure data, which increases the risk of misclassification of the exposure, and the potential for confounding.