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 QuestionnaireSpirometry

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

แบงตาม 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

• Strength : o 26 year period of follow upo Criteria for diagnosis ม objective confirmation : Skin prick test (atopy)

and lung funtion test (asthma)o Investigators ไมร outcome (no bias)o Adjustment of confounding variableso The strength of association : OR exceeding 2.0 mostly

• Weakness : o Criteria การ define เรอง BF ไมชดเจน แคกนนมแม อาจกนนมผสมรวมดวย ก

ยงอยใน BF group เพราะไมมขอหาม กนนมผสมปรมาณเทาไหรกไดรวมกบนมแม ทำาใหกลมตวอยางม heterogenitiy

o Recall bias o High drop out rateo No data กอนอาย 7 yo Prognostic factors ของ 2 กลมแตกตางกนตงแตแรกo Criteria of positive skin test (2 mm?) : just sensitizationo Selection of confounding factorso Self-selective biaso No data before age 9 y.

Appraising the Controversy & A Rebuttal

Pete et al.Pediatric Pulmonology 2003.35:331-4Sear et al.Pediatric Pulmonology 2003:36:366-8

Issues

– Heterogenicity of breast feeding groups – Recall bias & unclear whether recalled

reported were adjusted when the two methods differed

– 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?)

– Selection bias : hospital-based cohort & European ethnics only

– Confounding factors

– 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 intolater childhood which is consistent with most other studies

However no evidence of deleterious effectof 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 protectasthma 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 methodfor infantile feeding