breast feeding and asthma
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Breast Feeding & Asthma :Should we promote breast feeding?
It is not controversial that breast-feeding is the preferred method of infant nutrition
because of its nutritional, immunological, and psychological benefits
Effects on reducing early childhood wheezing, GI tract infections and atopic eczema (in early
life) was demonstrated by several studies
Effects on childhood asthma is controversial especially in mother who has asthma
Friedman et al.JACI 2005;115:1238-48
Sicherer et al.JACI 2008;122:29-33
Does breastfeeding protect against development of
atopy & asthma in childhood ?
ObjectiveTo assess long-term outcomes of asthma &
atopy related to breastfeeding in a New Zealand birth cohort study
Large unselected population-based birth cohort study
1,661 live-born
1,037 (91%) of 1,139 kids who were in Otago at age 3 y
5 7 9 11 13 15 18 21 26 yr
SPT aeroallergen
69% 87%
Verify BF record
(investigators unaware of outcome)
FH of allergy
Comprehensive Questionnaire
Spirometry
Metacholine challenge/
Bronchodilator response test
Investigators unaware of data for infant feeding determined all respiratory outcomes
• Current asthma = positive response to question “Do you (does your child) have asthma?” together with symptoms reported within previous 12 mo
• SPT to Dp, cat, dog , horse hair, rye grass, kapok, wool, fungus (positive = wheal > 2 mm than negative control at 15 min)
Methods
Results• 1,037 kids early childhood characteristics not
differ from 102 kids who did not participate• 45% (463) not breastfed• 7% (70) kids discontinued breastfed before 4 wk
• Mean duration of BF in BF group = 21.1 wk (SD 16.6)
• Term “BF” not necessarily mean exclusive BF
51% (533) BF < 4 wk 49% (504) BF >= 4 wk
Results• 1,037 kids early childhood characteristics not
differ from 102 kids who did not participate• 45% (463) not breastfed• 7% (70) kids discontinued breastfed before 4 wk
• Mean duration of BF in BF group = 21.1 wk (SD 16.6) : 4 wk until 47 wk
• Term “BF” not necessarily mean exclusive BF
51% (533) BF < 4 wk 49% (504) BF >= 4 wk
แบ่�งตาม preliminary
report : bias??
Characteristics of BF group
• First-born • Higher socioeconomic status • Non-smoking mothers • More likely to have a sheepskin on their bed
• Family history of hayfever or asthma (mother or father) and sex did not differ to non-BF group
Bias?
The effect with current asthma persisted
at all ages to 26 years
Effect of BF not effected by FH
1.72 --- 1.91 1.53 1.55
2.09 --- 2.54 1.86 1.73
Adjust SES, birth order, sheepskin use in infancy, maternal smoking
Conclusion
• No duration of exclusive BF had a protective effect against development of atopy & asthma in later childhood
• BF > 4 wks likelihood of skin test response to common allergens at age 13 y and more than doubled the risk of diagnosed asthma in mid-childhood, with effects persisting into adulthood
• Role of BF in protection of kids against atopy & asthma cannot be supported
Appraising the Controversy & A Rebuttal
Pete et al.Pediatric Pulmonology 2003.35:331-4Sear et al.Pediatric Pulmonology 2003:36:366-8
Issues
1. Heterogenicity of breast feeding groups
2. Recall bias & unclear whether recalled reported were adjusted when the two methods differed
3. Reporting bias : most mothers aware that a longer duration of breastfeeding is desirable
Answers
Breast feeding data was recorded systematically by interviewers at 3 years old and were compared with data recorded prospectively by nurse with 98.9% agreement
When data from nurse records were not provided : authors said they analyzed that it is not recall bias (how to?)
Giving mothers the benefit of the doubt would not lead to any significant difference in outcomes (how to show?)
4. Selection bias : hospital-based cohort & European ethnics only
5. Confounding factors
6. Causality : no dose response effect
Population-based birth cohort study
14,062 live
births
13,978 alive
at age 1 y 3 4 7 8
SPT aeroallergen
Verify BF record
Access
early childhood
wheezing
Spirometry &
Metacholine challenge
Ask whether diagnosed asthma
Methods
2 populations were accessed : - BF (never, <1 month, 1 to <3 months,
3 to <6 months, and >= 6 months)
- Exclusive breast-feeding (never,<4 months, >= 4 months)
SPT to 3 core aeroallergens (cat, mixed grass pollen, house dust mite)
- positive >= 2 mm than negative control at 15 min)
71.5 %
Adjusted by sex, maternal age, maternal smoking, environmental tobacco smoke , maternal asthma, maternal allergy, and older siblings
Maternal age and maternal history of allergy : most important confounders
57 %
55 %
Results
Slightly protective effect of breast feeding on wheeze in early life did not extend into later childhood which is consistent with most other studies
However no evidence of deleterious effect of breast feeding on atopic sensitization and later wheezing
• Bayesian joint model (reverse causation effect, loss follow-up group)
• Reverse causation effect = children with early wheezing were more likely to be breast-fed longer and to have
allergic outcomes
• Mean duration of breast-feeding for childrenwho did not wheeze in the first 3 months of life was 6.6 months compared with 8.9 months for children with wheeze (P < .0001)
Results
• modest difference in duration of breast-feeding based on early infant wheezing was not sufficient to bias the relationships between breast-feeding and the health outcomes examined
• No evidence that the pattern of missing data in this study appreciably influenced outcome
Results
Benefits• Large birth cohort study• Objective measurement• Bayesian joint model
Weakness• High drop-out rate• Criteria definition of atopy
Even breast feeding does not protect asthma or atopy in later life
Breastfeeding is a natural phenomenon, providing balanced nutrition and mother–infant bonding, as well as a number of health benefits
Breast feeding is still preferable method for infantile feeding