OBSERVATIONS ON ASTHMA

A review of the present understanding of asthma leads to the following conclusions: an elevated IgE is the principal risk factor in the deve lopment of childhood asthma; secondary exposure to a wide range of env ironmental agents (including indoor bioallergens) accounts for the var iations in prevalence; prevalence (defined by a positive answer to the question ''Have you ever had doctor-diagnosed asthma!'') ranges betwe en 4 and 8% in children. Black children have a slightly higher prevale nce than white children in the United States, and in both races boys h ave a higher prevalence than girls. A high prevalence is found in Puer to Rican children in the United States. Patterns of utilization of hea lth care resources (hospital emergency departments, individual physici ans, etc.) are dependent on economic circumstances. Low-income childre n have higher annual morbidity (days in hospital, days off school, etc .) than higher income children and are more dependent on hospital emer gency departments for primary care. Relatively little is known about n onatopic asthma in adults, although virus infections and occupational exposures play some part in its induction. There are some striking exa mples of asthma attack periodicity, and much may be learned from these . Hospital admissions for asthma have increased in many regions over t he past 15 years; it is unlikely that this represents the increased ad mission of milder cases and hence would indicate that asthma has becom e more severe. This is likely to be a more sensitive indicator of chan ge than mortality. Associations between indices of health effects and air pollutants indicate that these are probably playing a role in the worsening of asthma. Adverse effects related to SO2 and NO2 exposures have been documented, and fine particulate pollution (PM(10)) is also associated with worsening of asthma. Ozone is an intense respiratory i rritant, and, together with acid aerosols. may well be playing a role in the worsening of asthma. It is not known whether any of these agent s are affecting prevalence.