Study 1: Breast fed children have more atopy long term
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Breast fed children have more atopy well into adulthood, according to the
results of a recently published long term cohort study of children in New
Zealand.
Subjects: 1,037 New Zealand children entered into the study at age 3 years.
Method: Observational study. Breast feeding history was established at
entry into the study, and the children were reviewed at intervals of 2 to 5
years from age 9 until age 26, using respiratory questionnaires, pulmonary
function, bronchial challenge and skin allergy tests.
Results: Children who were breast fed for at least 4 weeks had more asthma
at each assessment than those who were not (p=0·0008), regardless of any
parental history of asthma or hay fever. See Table 1.
Table 1: Odds ratios for atopic manifestations at various ages
(after controlling for socioeconomic status, parental smoking, birth order,
and use of sheepskin bedding in infancy)
At age OR (95%CI) Signif.
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Asthma All ages 1.83 p<0·0001
(9 - 26 yrs) (1·35-2·47)
Any allergen +'ve 13 years 1·94 p<0·0001
(1·42-2·65)
Reference: Lancet 2002; 360: 901-07
Study 2: Breast fed children have more eczema to 7 yrs
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For each month of additional breastfeeding there is a higher risk of the
child developing eczema, according to results from a new German study.
Subjects: 1,314 infants born in Germany in 1990.
Method: Observational cohort study conducted over 7 years. Objective blood
tests as well as parent reports were used to establish the presence of
atopic eczema, as well as feeding history and family history of atopic
disease.
Children with family history of atopy were analysed separately from those
who developed non-eczema symptoms of atopy and from those with IgE evidence
of atopy. All other children formed a fourth sub-group.
Results: Although parental history of eczema was the strongest predictive
factor for the child developing the disease, in each of these three groups
there was an added risk for each month that the child had been breast fed
(odds ratio 1.03, 95% CI 1.002-1.06, p<0.04 in multivariate logistic
regression).
Reference: Clin Exp Allergy 2002 Feb;32(2):205-9
Study 3: Breast fed children have less atopy to 2 yrs
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A Swedish study found that breast feeding is associated with reduced risk
of a whole range of atopic manifestations in early childhood.
Subjects: 4,089 Swedish infants.
Method: Observational study. Parental questionnaire was used to assess
allergic symptoms and diagnoses at 1 and 2 years of age.
Results: Exclusive breast feeding for at least 4 months was associated with
a lower risk of a range of atopic disorders in children up to 2 years of
age. See Table 2.
Table 2: Odds ratio of atopic manifestations at age up to 2 years
OR (95%CI)
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Asthma 0.7 (0.5 - 0.8)
Allergic rhinitis 0.7 (0.5 - 1.0)
Multiple disorders* 0.7, (0.5 - 0.9)
* three or more of: asthma, suspected allergic rhinitis, atopic dermatitis,
food allergy related symptoms, suspected allergic respiratory symptoms
after exposure to pets or pollen
Reference: Arch Dis Child 2002 Dec;87(6):478-81
COMMENTS
These are just three of the many papers published on this important and
controversial topic, many within the last year. Another recent Australian
study along similar lines found that exclusive breastfeeding up to 4 months
of age is associated with a lower risk of asthma at 6 years of age (ref 1).
The whole topic is controversial because any research which suggests a
potential disadvantage of breast feeding in the early months of life is
bound to come under close scrutiny, given the importance of breast feeding
to public health worldwide.
On the other hand, there is much interest in the possibillity of reducing
the risk of atopic disease through dietary manipulation in early
childhood (ref 2).
Frankly, anyone looking at the latest study results could be forgiven for
remaining entirely confused on the main question: is a breast fed infant
more or less likely to develop atopic disease in later childhood and adult
life?
This apparent inconsistency is partly because the researchers are looking
at different aspects of atopy in children of different ages and using
different ways of measuring those outcomes.
Another problem is that, despite the best intentions of the researchers and
their careful statistical manipulations, it is not possible to entirely
control for confounding variables. There are many factors that could
conceivably influence both the mother's likelihood of breast feeding and
the risk of her child developing atopy. For example, the appearance of a
rash in the first months of life.
Some of the work in this area has been focused more on avoidance of foods
that might be potentially allergenic in high risk infants (such as cow's
milk), rather than on breast feeding itself (ref 3).
It is not surprising therefore that there is a lack of consensus amongst
doctors and nutritionists on this issue. Some meta-analyses have been done
- one Israeli group that has done several concluded that there is a
protective effect of around 30% from exclusive breast feeding during the
first 3 months of life against developing asthma, allergic rhinitis and
atopic eczema during childhood (ref 4,5,6).
If the opposite were true, it is not clear why breast feeding would
increase the risk of later atopy. One theory that has been proposed is that
breast fed children have less exposure to infections (which is true) and
that this lack of infections hampers the development of an efficient immune
system, compared with those who get more infections.
We do not believe that the evidence is strong enough as yet to reach a firm
conclusion one way or another. No doubt it would become clearer if we had
some results from randomised controlled intervention trials to look at. But
it will be difficult ethically to conduct such trials in light of the clear
advantages of breast feeding in so many other respects. So this whole issue
may remain uncertain for some time to come.
References:
1. J Allergy Clin Immunol 2002 Jul;110(1):65-7
2. Med J Aust 2002 Sep 16;177 Suppl:S78-80
3. Cochrane Database Syst Rev 2002;(3):CD003795
4. Acta Paediatr. 2002;91(3):275-9.
5. J Am Acad Dermatol. 2001 Oct;45(4):520-7
6. J Pediatr. 2001 Aug;139(2):261-6.
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