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Researchers hot on trail of an allergy epidemic
Researchers hot on trail of an allergy epidemic (Toronto Star, May 4, 2006)
By ELAINE CAREY, HEALTH REPORTER
Reproduced with permission of the Toronto Star
The air we breathe, the food we eat, the water we drink, even the kind of houses we live in and how well we clean them - all are suspects in the growing epidemic of allergies and asthma in Canada.
But just how they interact with our genes, so that one person develops an allergic reaction and another in the same environment doesn't, isn't clearly understood.
A new birth cohort study of 10,000 Canadian children that will follow them from the time their mothers are pregnant, possibly through to adulthood, could provide some of those basic answers.
The study, the largest of its kind in the world, will be funded by the AllerGen project, one of the federal government's Networks of Centres of Excellence, based at McMaster University, and will draw on the expertise of more than 170 researchers at 23 universities across the country. Health Canada and the Canadian Institutes of Health Research are also being approached for funding.
"Canada has been very, very well positioned for a long time in the allergy and asthma field," says Dr. Judah Denburg, director of AllerGen (Allergy, Genes and Environment Network) and a professor in immunology at McMaster.
The study will start with pregnant mothers because "if you start when the kids are born, you lose all the information the mothers may have given you about their life, exposures and health during the pregnancy," he says.
"Probably the best approach is to get people as soon as possible after they become pregnant, study the mother, the father and focus on them and on all the circumstances during the pregnancy and then follow the babies and the families."
Canada is near the top of the list of countries facing a growing epidemic of allergies such as hay fever, eczema, asthma, reactions to foods or pets, and life-threatening anaphylaxis. Nearly half of Canadians suffer from some sort of allergic reaction and 15 to 20 per cent of children have asthma.
"We're now at the point where we want to try to understand why allergy and asthma are increasing, particularly related to environmental exposures, housing, and air pollution, indoors and out," says Dr. Malcolm Sears, director of the Firestone Institute for Respiratory Health at St. Joseph's Healthcare in Hamilton and a member of the AllerGen team.
"We want to examine many different aspects of the environment - where people are living, their exposure to animals, to farms, the climate."
"A major development over the past decade has been understanding that diseases are not all related to genetics or the environment but the interaction of the two," Sears says.
"Sometimes, a particular environment increases an allergy in one genetic type and decreases it in another. It's a complicated question we're trying to answer without getting into an impossibly complicated study."
Allergies are also increasing rapidly in some developing countries where the rates were previously low.
The best example began with the fall of the Berlin Wall in 1989, Sears says. Children in East Berlin had very low allergy and asthma rates, even though they came from the same gene stock as those in West Berlin. But the rates increased rapidly as they adopted more westernized lifestyles.
"That's one evidence that strongly supports the fact the environment, whether air quality, food or housing, may have a major impact," he says.
Genes don't change rapidly over two or three generations but the environment has, he adds.
"For example, the way houses are built is now quite different than 30 or 40 years ago. Leaky windows and doors are now quite well sealed to conserve energy, but it may be less good for allergies that we don't have fresh air blowing through. The amount of mould that develops in a building may have some impact, even the number of diesel trucks that pass by a house. They could all be aspects."
The researchers also want to learn whether children with lung obstructions are born that way, or develop them later. They have developed new techniques to measure lung capacity in very young children, including a tiny vest babies will wear.
"There's not a study in the world that will have all this incorporated into it," says Denburg.
They hope to recruit a broad range of families from a variety of housing types, air environments and climates from across the country.
The researchers will continue to follow the children and their families "until investigators are no longer interested or the funding runs out," says Sears. The initial focus will be on the first three or four years of their lives.
AllerGen is receiving $5 million to $5.5 million a year in operating funds from Ottawa because "Canada wants a tactical response to the allergy epidemic," says Denburg.
"It's quite clear that more and more people are suffering from allergies, and it goes back in age to the first year of life, where kids are coming up with food allergies they never had before, and it goes right through life."
"People who never had allergies are now developing them in their 30s, 40s and 50s," Denburg says.
"We found enough evidence and put together a proposal to the Networks of Centres of Excellence to say, `Look, we have the expertise in Canada but we don't have the glue to bring everyone together. We really need to come up with some answers."
"Mothers come to me and say, `Should I be feeding my kids peanuts or not? Should I be breastfeeding? What should I be doing?' We're not really totally there yet in terms of what the right advice is to give people."
"We will be able to focus on select factors and say much more relevant things about what you should do and shouldn't do. We're going to see it as it develops. This is not a retrospective study. This is excitingly different."
(Toronto Star, May 4, 2006)
