What is the question?

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

What is the answer to the question?

• A conclusion about the relationship between shorter versus longer durations of any human milk feeding and celiac disease could not be drawn due to concerns about reverse causality across the body of evidence. 

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 celiac 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 celiac disease. 
• It is not clear whether the findings show how the duration of human milk feeding affects celiac disease or how celiac disease affects the duration of human milk feeding, so the systematic review question cannot be answered.

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 celiac 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 celiac disease, only, to ensure that it addresses the relationship of shorter versus longer durations of any human milk feeding with celiac 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

• A conclusion about the relationship between shorter versus longer durations of any human milk feeding and celiac disease could not be drawn due to concerns about reverse causality across the body of evidence. 
  
  Grade: Grade Not Assignable

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; 4 articles presented nested case-control or prospective cohort data analyses and the remaining 5 were case-control studies. 
• The systematic review question could not be answered due to concerns about reverse causality across the body of evidence.