Periodicity of asthma, emphysema, and chronic bronchitis in a northwest health maintenance organization

Study objective: Since seasonal patterns in morbidity may identify triggers provoking hospital-based care for airflow obstruction, this study examined seasonal variation in patterns of hospitalizations for asthma, chronic bronchitis, and emphysema. Design and setting: The data for this analysis were derived from the abstracted medical records of a large health maintenance organization, Kaiser Permanente, Northwest region, over the period 1979 to 1987. Patients: In all, 2,060 primary hospital discharges for asthma and 1,121 primary hospital discharges for the combination chronic bronchitis/emphysema were observed. Results: The monthly patterns varied for asthma and chronic bronchitis/emphysema, and also varied by age and sex. For young children 0 to 14 years, asthma hospitalizations peaked primarily in the fall. In contrast, for young children 0 to 14 years, hospitalizations for chronic bronchitis/emphysema peaked in the fall/winter months. Seasonal variation decreased as age increased for chronic bronchitis/emphysema, such that for the 65+ year group, there was no seasonal variation. Conclusion: A better understanding of the causes of the age-specific seasonal patterns in these obstructive respiratory diseases may help to reduce the morbidity that is associated with them.