Incidence and prevalence of physician-diagnosed asthma in a suburban population of young adults

Background: Asthma is a common chronic disease of both children and adults, but there have been few reports of the incidence of asthma in well defined adult populations. Objective: To determine the incidence and prevalence of asthma in a population of young adults living in suburban Detroit. Methods: As part of a study of the development of allergic disease in children, the parents of 841 study children, from a defined, well characterized population, were questioned about their personal histories of allergic disease, including asthma, during the mother's pregnancy. The children have been followed from birth until 4 years of age. When the child became 4, the parents were again questioned about allergic disease. Those reporting asthma when the child was 4 but not prior to the child's birth, were recontacted to confirm that they had been diagnosed by a physician as having asthma in the 4-year interval. Because of prior reports concerning racial differences in the prevalence of asthma and the small number of non-white mothers in the study population, calculations of asthma prevalence and incidence were limited to the 750 mothers, who described themselves and their baby's father as white. Results: The parents studied were young adults mean age 28.7 [(standard deviation (SD) 4.5 years] and 31.0 (SD 5.0) years, of mothers and fathers, respectively. These parents were relatively well educated with 30.7% of mothers and 43.5% of fathers having college degrees. The initial prevalence of a previous physician diagnosis of asthma was 7.5% [95% confidence interval (95% Cl) = 5.7-9.6] in the mothers and 6.9% (95% Cl = 5.2-9.0) in the fathers, yielding a total prevalence of 7.2% (95% Cl = 5.9-8.7) in these 1484 adults. Five hundred thirty-three mothers and 498 fathers (total = 1031), who did not report asthma during the mothers' pregnancies, were available for questioning when the children were 4 years old. The average yearly incidence of asthma was 5.2 (95% Cl = 2.6-9.2) per 1000 in the mothers and 1.5 (95% Cl = 0.3-4.4) per 1000 in the fathers (P = .058), with an overall incidence of 3.4 (95%Cl = 1.8-5.7) per 1000. The average yearly incidence was 5.3/1000 in those <30 years old and 1.5/1000 in those greater than or equal to 30 years of age (P = .056). Conclusions: We conclude that the incidence of asthma in this population of relatively young, well educated, white adults is approximately 3.4 per 1000 per year and that newly diagnosed asthma was more common in women and in those <30 years of age.