Purpose of the Study
To present data on age- and sex-specific patterns of change in an analysis of a 20-year trend in treated prevalence of asthma among members of a large health maintenance organization (HMO).
Data were derived primarily from the abstracted medical records of a random sample of Kaiser Permanente (KP), Northwest Division, members and from an eligibility file that tracks health plan eligibility for members included in the outpatient utilization sample.
Data are presented for each of six age and sex categories, and include both the treated prevalence of the broader category of chronic airflow obstruction (CAO), defined as asthma, chronic bronchitis, or emphysema. The three age groups were: 0 to 14-year-olds, 15- to 64-year-olds, and 65+ years.
Three main findings emerged from this study. First, for the 20-year period from 1966–1987 the treated prevalence of asthma increased steadily and significantly in this population in both males and females and in all age ranges except males over 65 years of age. Second, these increases parallel increases in the broader category of CAO and therefore are not likely merely to reflect diagnostic shift from chronic bronchitis/emphysema toward asthma in the midst of an otherwise stable pattern of chronic airways disease. Third, these results also demonstrate the dangers of extrapolating trends in one type of asthma health care utilization outcome, for example hospitalizations, to other types of health care utilization outcomes.
These findings support other evidence of a real increase in asthma prevalence.
Epidemiologic studies similar to this report are extremely important in assessing changes in prevalence as well as the changing nature of health care outcomes. A comprehensive evaluation of hospitalizations, emergency department visits, days lost from school or work, medication requirements, etc will be important in understanding the impact of our environment as well as the success or failure of our treatment strategies.