Increase in admission threshold explains stable asthma hospitalization rates.

Background: Asthma morbidity and mortality has increased substantially in recent years, but asthma hospitalization rates among many geographic and sociodemographic groups have remained stable. Observations on asthma hospitalization rates and severity of acute episodes might provide valuable insight into the functioning of the health care system during this period of health care reform.

Objective: To analyze changes between 1991 and 1995 in childhood asthma hospitalization rates and severity of acute episodes.

Design And Methods: All 29 329 hospitalizations, including 2028 for asthma, for the 198 893 children (<19 years of age) in Monroe County (Rochester), New York, were studied during this 5-year period. Severity was determined by hospital record review on a 22% random sample. Using the worst oxygen saturation (SaO(2)) during the first 24 hours of hospitalization as the primary index of severity, episodes were categorized as mild (0 to >/=95), moderate (90 to 94), or severe (<90).

Results: Hospitalization rates are expressed as hospitalizations per 1000 child-years. The overall asthma hospitalization rate was 2.04 (95% confidence interval, 1.95-2.13). The overall annual asthma hospitalization rate remained relatively stable from 1991 (1.90) to 1995 (2.31), whereas the hospitalization rates for severe asthma rose 270%-from 0.57 to 1.55-during this period. Simultaneously, the hospitalization rates for mild asthma decreased from 0.26 to 0.12. As a proportion of all asthma hospitalizations between 1991 and 1995, severe episodes increased from 31.5% to 60.4%; conversely, mild episodes decreased from 14.1% to 4.7%.

Conclusions: Severity increased significantly among children hospitalized for asthma while the overall asthma hospitalization rate remained stable. It seems that the health care system in this community has responded to an increase in severity of asthma by raising the severity threshold for admission.