They are ugly, multi-legged creatures about one-tenth of a millimetre long. They tend to congregate in mattresses or in carpets around a bed so they can be close to their food supply—dead human skin, the tiny bits that scale off every time a sleeper rolls over. The predators are called house dust mites, and they are not just grossly unattractive. Now, according to medical researchers in the United States and Canada, mites are probably one of the factors—and perhaps the major one—behind a sharp increase in the development of asthma among young children.
The latest evidence in the continuing search for the causes of asthma emerged last week when a research team headed by Dr. John Yunginger of the Mayo Clinic in Rochester, Minn., published findings showing that Rochester-area children were two to three times as likely to have had the disease in 1983 as in 1964. In its report in the American Review of Respiratory Disease, the Yunginger group speculated that more children may be developing asthma—a disease that is characterized by coughing, wheezing and difficulty in breathing—because energy-conscious parents are unwittingly adding to indoor air pollution by sealing homes more tightly. The tighter seal, he said, creates a warmer and more humid environment that encourages the accumulation of dust mites. Allergies, doctors have long believed, are a principal cause of asthma in children, a disease that is seldom fatal but can cause severe distress and seriously inhibit a child’s physical activity. The study looked at all age groups, but found increases in asthma cases only among children.
In Canada, researchers in Winnipeg and Vancouver began collaborating in January on a one-year, $500,000 comparative study of indoor and outdoor environments to identify factors that may play a role in causing asthma. Dr. Allan Becker, a 47-year-old associate professor of allergy and clinical immunology at the University of Manitoba, said that researchers, using 60 homes in each city, are examining a variety of factors that may be involved in triggering asthma attacks, including dust mites, cat and dog hair and weather patterns.
Although members of the two-city project have not yet published any conclusions, Becker said that he believes asthma can be aggravated when the sufferer breathes in the allergyinducing substance from dust mites—their microscopic fecal pellets and other particles. Vacuuming rugs or beating mattresses will not get rid of the parasites, Becker said. The recommended course of action on behalf of children who may be allergic to mites: seal mattresses
in plastic to cut off the food supply of the parasites. Those precautions are particularly important, declared Becker, “because there seems to be a real and true increase in the prevalence of asthma, not only among very
young children but among older ones as well.” Dr. Gerard Canny of Toronto’s Hospital for Sick Children asthma clinic said that the number of youngsters hospitalized with the ailment has risen by 200 per cent during the past 20 years. And while the legions of dust mites being incubated in better-insulated homes may be partly to blame, “it may also be that we are now diagnosing more patients, and also diagnosing as asthmatic, cases we used to call bronchitis and other things.” For the estimated 300,000 Canadian children who suffer from asthma, the new attention being paid to the disease could eventually help them to breathe more easily.
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