Prevalence and treatment of asthma in the Michigan Medicaid patient population younger than 45 years, 1980-1986.

The prevalence and outpatient treatment of asthma were studied in the Michigan Medicaid patient population by use of computerized physician, hospital, and pharmacy reimbursement data to mark and track asthma-related medical transactions. Asthma cases were defined as patients with evidence of at least two diagnoses and prescription drug transactions consistent with asthma. More than 52,000 cases were thus identified. The period prevalence of asthma was estimated on a year-by-year basis. The prevalence of asthma in the population increased from 2.0 per 100 Medicaid patients in 1980 to 2.8 per 100 Medicaid patients in 1986. Prevalence decreased with age until the age of 20 years and increased thereafter, and was higher in male children than in female children. In contrast, asthma was more prevalent in female adults than in male adults. Prevalence was higher in black subjects than in other races and higher in urban residents than in rural residents. The total number of reimbursements for antiasthma medications increased from 60,000 per year to 120,000 per year, and the average number of antiasthma prescriptions per Michigan Medicaid asthma case increased at the rate of 6.6% per year during the study interval. Changes in the preferred types of asthma treatment consistent with changes that have occurred in the general population were observed. These data suggest that the relative and absolute occurrence of asthma and asthma treatment in the Michigan Medicaid population is increasing.