UBC Reports | Vol. 46 | No. 16 | Oct. 19, 2000

Changes in environment may prevent asthma: study

Disease is most common chronic respiratory disease among children in Canada

by Hilary Thomson staff writer

Breast-feeding, controlling dust mites and eliminating second-hand smoke are some of the interventions that may prevent asthma in infants, according to Prof. Moira Chan-Yeung. Yeung is principal investigator in a study recently published with UBC researchers Helen Ward and Alexander Ferguson and two University of Manitoba professors.

"The results of the study are very encouraging because they suggest that asthma can be prevented, not just managed," says Chan-Yeung, a professor of Respiratory Medicine who specializes in asthma.

The research team studied 545 high-risk infants -- babies closely related to individuals with asthma or similar allergic disease -- from birth to age one.

Conducted in Vancouver and Winnipeg, the study is the first in Canada to evaluate the effectiveness of a multi-faceted intervention program in the primary prevention of asthma in this group.

Researchers found that in families who made a number of changes in their environment, 38 infants had possible or probable asthma compared to 49 babies in the control group.

"The prevalence of asthma has increased in developed countries in the last 20 years, but methods to prevent asthma have not been well studied," says Chan-Yeung.

She and UBC colleagues Ward, an associate professor of Respiratory Medicine and Ferguson, a professor of Pediatrics and head of the Allergy division, assessed participants' homes for a variety of asthma triggers.

Water damage, leaks and dampness, type of heating and air-conditioning, number and types of pets and number of tobacco smokers were all evaluated.

Intervention measures included encasing mattresses and box springs in the parents' and infants' bedrooms in vapour-impermeable covers. Parents were also instructed to wash all bedding in hot water weekly.

Keeping pets outdoors and not taking the baby to smoky environments were also recommended.

In addition, mothers were encouraged to breast-feed for at least four months. During the last trimester of pregnancy and while nursing, they followed a diet that excluded peanuts and other nuts, fish and other seafood. The same foods and cows' milk were eliminated from the infant's diet for the first year.

In the study, symptoms of possible asthma included at least two distinct episodes of cough each lasting for two or more weeks or at least two distinct episodes of wheeze each lasting one or more weeks.

Probable asthma symptoms included these symptoms plus at least one of: nocturnal cough at least once a week in the absence of a cold; exercise-induced cough or wheeze; and response to treatment with anti-inflammatory drugs.

Next steps for the research group include a follow-up study of this group at seven years of age to determine if the beneficial effects of the intervention measures are still present.

Asthma is the most common chronic respiratory disease of childhood. It affects about seven to 10 per cent of children and accounts for one-quarter of school absenteeism in Canada according to the Canadian Lung Association.

Approximately 20 children and 500 adults die from asthma each year in Canada.

The Respiratory Health Network of Centres of Excellence was a major suppporter of the study.