ABSTRACT
Although allergy is an established risk factor for the development of asthma in children and adults, the role of atopy in fashioning the prognosis of asthma in adults is unclear (46) (Table 7). Some studies have shown that atopy is less important in adults than in children, although this could be due to diagnostic bias (47). In addition, there are difficulties in interpreting some of the studies, as IgE levels and the manifestations of allergy change with age: cigarette smoking increases IgE levels, and the effects of therapy may affect outcomes. There is even controversy about the separation of asthma into allergic and nonallergic varieties, as Burrows and colleagues (48) showed in a general population study, indicating that the prevalence of asthma was closely associated with serum IgE levels (P < 0.0001). In this study, the log odds for asthma risk increased linearly with serum IgE after controlling for possible confounders, and no asthma was present if the IgE level corrected for age and sex was <1.46 SD below the mean. In a longitudinal study of men with a mean age of 64 years, a rise in IgE antibody to dust mite preceded the onset of wheeze (49). In the Dutch study of Panhuysen et al. (33), lower serum IgE level predicted absence of asthma on follow-up. Atopy has been shown to be a risk factor for decline in lung function independent of asthma status in a number of studies (7 ,43,50), but other studies have not shown this in working or general populations (27,51).
