Effect of environmental manipulation in pregnancy and early life on respiratory symptoms and atopy during first year of life: a randomised trial

doi:10.1016/S0140-6736(01)05406-X

The Lancet

Volume 358, Issue 9277, 21 July 2001, Pages 188-193

https://doi.org/10.1016/S0140-6736(01)05406-X Get rights and content

Summary

Background

Asthma places huge demands on health-care services, and its prevalence is increasing. Reduction of exposure to environmental allergens could offer a realistic chance for primary prevention. Our aim was to ascertain whether or not living in a low-allergen environment reduces the risk of asthma and atopic diseases in infants.

Methods

We assigned infants to four risk groups according to parental atopic status. We enrolled 291 high-risk couples (both parents atopic, no pets) into a prospective, prenatally randomised, cohort study, and allocated them to environmental manipulation, in which measures to reduce prenatal and postnatal allergen exposure were undertaken (active HRA) (n = 145) or no intervention (control HRC) (n=146). Two further prospective groups were studied: 161 high-risk infants with pets in the home (HRP group) and 168 low-risk infants, whose parents were both non-atopic (LR group). The main outcome measures were signs and symptoms of atopic disease at 1 year of age.

Findings

103 families dropped out or were lost to follow up. At age 1 year we followed-up 133 HRA, 118 HRC, 140 HRP, and 126 LR infants. Children in the HRA group were less likely to have respiratory symptoms during the first year of life than those in the HRC group. The most pronounced differences were in the relative risks for severe wheeze with shortness of breath (relative risk 0·44 [95% CI 0·20–1·00]), prescribed medication for the treatment of wheezy attacks (0·58 [0·36–0·95]), and wheezing after vigorous playing, crying, or exertion (0·18 [0·04–0·79]). Probability of respiratory symptoms in HRC and HRP infants was similar, whereas it was much lower in the LR than in the HRC group. Cat ownership was significantly associated with sensitisation to cats (24·6 [3·04–199·05]; p=0·003).

Interpretation

Environmental manipulation reduces some respiratory symptoms in the first year of life in high-risk infants. Further follow up is needed, however, to ascertain whether living in a low-allergen environment reduces allergy and asthma in later life.

Introduction

Sensitisation to indoor allergens is a major risk factor for asthma,¹ and there is a dose-response relation between allergen exposure and sensitisation.2, 3 Although the importance of exposure in progression from sensitisation to asthma is less certain,⁴ reduction of exposure to allergens might offer a realistic opportunity for primary prevention of atopy and asthma.5, 6 The National Asthma Campaign Manchester Asthma and Allergy Study (^NACMAAS) is investigating whether or not stringent environmental manipulation can prevent sensitisation and allergic disease in children at high risk of atopy. We previously reported that practical acceptance of this regimen was excellent, and that it achieved and maintained exposure to low-allergen concentrations during pregnancy and in the first year of life.⁷ Here, we present data on the effect of environmental manipulation on symptoms during the first year of life. For comparison, we also include data from two non-randomised but similar groups of infants—ie, those at high risk with pets and those at low risk without pets.

Section snippets

Study population

^NACMAAS is a prospective, prenatally randomised, cohort study. Detailed description of screening and recruitment is provided elsewhere.⁸ Briefly, all pregnant women and their partners were screened at “booking” antenatal visits. Both parents completed a questionnaire and had skin testing. Couples who agreed to take part were allocated to risk groups according to their atopic status, history of allergic disease, and pet ownership.

Couples were randomly allocated (stratification by maternal

Results

The figure shows the trial profile. 89 families withdrew before the birth of a child, and 14 were lost to follow-up after the birth of a child. 517 participants completed the follow-up at age 1 year: 133 HRA, 118 HRC, 140 HRP (66 cat owners, 60 dog owners, 14 owned cats and dogs), and 126 LR. Table 1 shows demographic data for these infants.

Table 2 shows the frequency of signs and symptoms suggestive of atopic diseases in the four groups. Table 3 shows the relative risks and 95% CI for

Discussion

Our results suggest that environmental manipulation can reduce respiratory symptoms in infants aged 1 year or younger, who are at high risk of allergic disease. These are preliminary results, however, and should not be used as the basis for advice on clinical management, since further follow up is needed to ascertain whether or not living in a low-allergen environment reduces frequency of allergy and asthma in later childhood.

The stringent environmental manipulation regimen that we used was

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In a population-based birth cohort we measured mite, cat, and dog allergen levels in dust samples collected from homes within the first year of life. Sensitization was assessed at 6 time points between infancy and age 16 years. Genotyping was performed for 6 FLG mutations.
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Environmental exposures have been recognized as critical in the initiation and exacerbation of asthma, one of the most common chronic childhood diseases. The National Institute of Allergy and Infectious Diseases; National Institute of Environmental Health Sciences; National Heart, Lung, and Blood Institute; and Merck Childhood Asthma Network sponsored a joint workshop to discuss the current state of science with respect to the indoor environment and its effects on the development and morbidity of childhood asthma. The workshop included US and international experts with backgrounds in allergy/allergens, immunology, asthma, environmental health, environmental exposures and pollutants, epidemiology, public health, and bioinformatics. Workshop participants provided new insights into the biologic properties of indoor exposures, indoor exposure assessment, and exposure reduction techniques. This informed a primary focus of the workshop: to critically review trials and research relevant to the prevention or control of asthma through environmental intervention. The participants identified important limitations and gaps in scientific methodologies and knowledge and proposed and prioritized areas for future research. The group reviewed socioeconomic and structural challenges to changing environmental exposure and offered recommendations for creative study design to overcome these challenges in trials to improve asthma management. The recommendations of this workshop can serve as guidance for future research in the study of the indoor environment and on environmental interventions as they pertain to the prevention and management of asthma and airway allergies.

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ArticlesEffect of environmental manipulation in pregnancy and early life on respiratory symptoms and atopy during first year of life: a randomised trial

Summary

Background

Methods

Findings

Interpretation

Introduction

Section snippets

Study population

Results

Discussion

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Effect of environmental manipulation in pregnancy and early life on respiratory symptoms and atopy during first year of life: a randomised trial