Primary Prevention in Infants of Mothers Who Have Asthma
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The National Asthma Campaign Manchester Asthma and Allergy Study (NACMAAS)
Article Citation(s):
Custovic A, Simpson BM, Simpson A, Kissen P, Woodcock A. Effect of
environmental manipulation in pregnancy and early life on respiratory
symptoms and atopy during first year of life: A randomized trial. Lancet
2001; 358:188-93.
Intervention Setting:
Participants’ homes
Target Population:
Pregnant women attending antenatal clinics and their partners in
Manchester, United Kingdom
Program Description:
This prenatal study investigation sought to determine whether
stringent environmental manipulation could prevent sensitization and
allergic disease in children at high risk for atopy. Investigators
hypothesized that reduced exposure to allergens might offer a realistic
opportunity for primary prevention of atopy and asthma. Couples who
agreed to take part were allocated to risk groups according to their
atopic status, history of allergic disease, and pet ownership. The first
two groups included couples in which both parents were atopic, the
mother was sensitized to indoor allergens, and no cat or dog was in the
house. The first group was a stringent environmental manipulation group,
the intervention group, and the second was a high-risk control group.
The third group was a high-risk pet group where both parents were
skin-test positive, and they had a cat and/or a dog. The fourth group,
the low-risk group, had parents who were both skin-test negative, had no
history of atopic disorders, and had no pets. Interventions for the
intervention group included covering the maternal bed (pillow, mattress,
and quilt) with allergen impermeable bedding during pregnancy and after
delivery, use of a high-filtration vacuum cleaner, removal of carpets in
the infants’ room and replacement with a vinyl floor, and provision with
new custom-made cot and carrycot mattresses encased in allergen-proof
material during the manufacturing process. Participants were asked to
wash their infant’s linen in hot water once a week, and benzyl benzoate
was applied to carpets and soft furnishings throughout the rest of the
house.
The follow-up clinical and subsequent home visits were identical in all four groups of infants. Parents and children were invited into the clinic within 2 weeks of the child’s first birthday. An interviewer administered a standard questionnaire, and a physical examination was completed to identify the presence of respiratory symptoms or eczema, or both, in children and the use of medication. The severity and frequency of wheeze and wheeze with shortness of breath were assessed, and the medications used to treat wheezy attacks were documented. Skin-prick tests for six common allergens were conducted (D pteronyssinus, cat, dog, mixed grasses, milk, and egg).
Evaluation Design:
A randomized cohort approach was used.
Sample Size:
A total of 517 people participated in the four study groups
Outcome Measures/Results:
Signs and symptoms of atopic disease at age 1 year for children born
to study couples were the outcome measures. Children in the high-risk
intervention group were less likely than those in the high-risk control
group to have respiratory symptoms during the first year of life. The
most pronounced differences were in the relative risks for severe wheeze
with shortness of breath: relative risk 0.44 (95% confidence intervals
0.2-1.00), prescribed medication for the treatment of wheezy attacks:
relative risk 0.58 (95% CI 0.36-0.95), and wheezing after vigorous
playing, crying, or exertion; relative risk 0.18 (95% CI 0.04-0.79). The
probability of respiratory symptoms in the high-risk control group and
high-risk pet group infants was similar; however, it was much lower in
the low-risk than in the high-risk control group. Cat ownership was
significantly associated with sensitization to cats. These findings
support a dose-response relation between exposure to cat and specific
sensitization, at least in early life. Dog ownership was not associated
with either sensitization to cats or dogs. The protective effect of
environmental manipulation was limited to respiratory symptoms, and the
relative risks for other symptoms suggestive of atopic disorder (eczema
and allergies to food) were almost identical in the three groups of
high-risk infants.
Materials available:
None
Medical clinics/physicians’ offices
Prenatal Intervention with First-degree Relatives who have Diagnosed Asthma
Article Citation:
Chan-Yeung M, Manfreda J, Dimich-Ward H, Ferguson A, Watson W,
Becker A. A randomized controlled study on the effectiveness of a
multifaceted intervention program in the primary prevention of asthma in
high-risk infants. Archives of Pediatric Adolescent Medicine
2000;54:657-63
Intervention Setting:
The intervention was conducted in Vancouver, British Columbia and
Winnipeg, Manitoba and included a) women registered to give birth at a
community-based maternity hospital, and b) women attending
university-based antenatal clinics in offices of obstetricians.
Target Population:
The intervention targeted pregnant women identified in prenatal
clinics who would be mothers of infants determined to be at high-risk
for asthma. Infants are defined as persons from birth through 1 year of
age. High-risk infants are defined as those with at least one
first-degree relative with asthma or two first-degree relatives with
other IgE-mediated allergic disease.
Program Description:
The objective of this study was to determine the effectiveness of a
multifaceted intervention program in the primary prevention of asthma in
high-risk infants. The program included the following strategies:
avoiding of house dust mites (HDMs), pet allergens, and environmental
tobacco smoke; encouraging breastfeeding and supplementation with
partially hydrolyzed formula; and avoiding foods that sensitize. After
completing the baseline assessment, the intervention group participants
were given instruction regarding steps to reduce exposure to HDMs; in
addition, they were advised to remove pets from the home and to
eliminate exposure to environmental tobacco smoke. Mothers were advised
either to breast feed for at least 4 months or use partially hydrolyzed
formula and avoid eating certain foods.
Evaluation Design:
The study was a randomized controlled trial. Home visits were
conducted before the birth of the infant and at 2 weeks and 4, 8, and 12
months after birth. Homes were assessed using a questionnaire and a
walk-through survey. During each visit, data were collected regarding
evidence within the home of leaks resulting in water damage and mildew
and molds. The type of heating/air conditioning system functioning
within the home was also documented. During further home visits, a
questionnaire addressing the infant’s health and environment was
administered.
Sample Size:
The study participants included 251 infants in the intervention
group and 242 infants in the control group.
Outcome Measures/Results:
Outcome measures were probable or possible asthma, rhinitis without
apparent colds, and skin test results positive for common inhalant
allergens. Thirty-eight (15.1%) of the 251 infants assessed in the
intervention group met the criteria for possible or probable asthma; 49
(20.2%) of the control-group infants met the same criteria. In the
intervention group, 16.7% of the infants, and in the control group,
27.3% of the infants developed rhinitis without colds, a modest but
statistically significant difference. Incidence of skin test results
positive to one or more inhalant allergens was similar in both groups
(4.4% in the intervention group and 4.6% in the control group).
Availability of Protocol/Materials:
The protocol and materials are not available for widespread
distribution.
Case Study:
None
