Background: Adult-onset asthma is frequently encountered in primary care and is responsible for a large proportion of asthma morbidity and mortality. The primary goal of this survey was to describe the epidemiology of diagnosed and possible undiagnosed asthma in Wisconsin Research Network (WReN) practices.
Methods: Physicians from 59 practices interviewed a systematic sample of their clinical population, which included all patients encountered during office visits one day each week for 3 or 12 months, to obtain a history of physician-diagnosed asthma or symptoms suggesting undiagnosed asthma (wheezing and shortness of breath). Age at diagnosis or at onset of symptoms and current disease activity were also recorded.
Results: The 14,127 patients surveyed closely resembled the age-sex composition of the 1990 general and family practice component of the National Ambulatory Medical Care Survey. Physician-diagnosed asthma that was active within the previous year was reported by 6.1% of WReN patients (5.8% of patients younger than 20 years of age and 6.2% of adults). Undiagnosed asthma that was active within the previous year was reported by 3.3% (2.9% of patients younger than 20 years of age and 3.4% of adults). Adult-onset asthma was reported by 46.3% of all patients with diagnosed asthma; and 56.7% of patients with undiagnosed asthma reported that their symptoms began in adulthood.
Conclusions: Adult-onset asthma accounts for approximately one half of all asthma cases. Since most patients with adult-onset asthma are managed by primary care physicians, practice-based research is necessary for the understanding, treatment, and possible prevention of this important disease.