SAN FRANCISCO- The incidence of asthma is increasing at an alarming rate, mostly as a side effect of poverty, according to leading experts.

According to the most recent studies from the Centers for Disease Control, five percent of the U.S. population has some kind of respiratory disease. In the past ten years the number of asthma cases has increased 40 percent, with the greatest gains seen among women and the poor.

Very few patients die from asthma. Even so, the asthma mortality rate increased by 40% in the U.S. between 1982 and 1991. The mortality rate rose an alarming 59 percent among women, and blacks. Women and blacks are now nearly seven times as likely to die from asthma as whites, according to the CDC. Hospitalization for asthma, as well as emergency room visits for acute attacks are also on the rise.

"There is mounting evidence that asthma prevalence, morbidity and mortality are increasing in the U.S. and many other Western countries. The reasons for these trends are not clear but are probably complex and involve a number of factors," notes A. Sonia Buist, M.D., Head, Pulmonary and Critical Care Medicine, Oregon Health Sciences University, Portland, Oregon.

The development of clinical asthma depends on the presence of host factors, environmental factors and additional co-factors. Host factors include the genes involved with the bodies response to allergens and gene involved with the pulmonary inflammatory response. Very little is know about the genetic basis of asthma.

Air pollution is often assumed to play a role in the increasing incidence of asthma. Yet air quality has actually improved significantly in many major urban areas in recent years, notes Dr. Buist. Two recent articles in the New England Journal of Medicine show no relation between asthma mortality rates and the concentration of major air pollutants. However, these studies do indicate a higher mortality rate among those living below the poverty line.

It is more likely that aeroallergens in the indoor environment are important factors in the rise of asthma. These include house dust mites, cockroaches and cats. Outdoor aeroallergens, particularly pollens, are also known to play an important role. Other cofactors include tobacco smoke, air pollutants and gases such as ozone and nitrogen dioxide. Respiratory viral infection, seen to be increasing as more children attend daycare centers, may also be a factor, she says.

Many of the known risk factors for asthma are associated with poor housing conditions. House dust mites are more prevalent in old furniture, carpets and drapes. Molds are also more prevalent in poor housing conditions. The poor also tend to live in more polluted areas and also tend to have inadequate access to appropriate health care, she notes.

"The challenge is to identify patients at risk and to intervene appropriately to reduce their risk of hospitalization and death," stresses Dr. Buist. A program initiated by the National Heart, Lung and Blood Institute emphasizes that asthma should be treated as a chronic inflammatory disease; that environmental factors should be taken seriously; and that a partnership between patients and health care providers that includes health education is crucial to optimal asthma management, she said.

Dr. Buist spoke recently at a UCSF-sponsored conference on asthma management. The asthma statistics appeared in the CDC's Morbidity and Mortality Report, 1/6/95. The environmental studies appeared in NEJM '94; 331:1542-6.

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