Objective: To measure changes between 1991 and 1995 in childhood asthma hospitalization rates and severity. Design/Methods: All 2,028 asthma hospitalizations during this 5-year period for the 198,593 children(<19 yr) in Monroe County (Rochester), NY were studied. Severity was determined by hospital record review on a 22% random sample. Using the worst SaO2 during the first 24 hours of hospitalization as the primary index of severity, cases were categorized as mild (>94), moderate (90-94), or severe(<90). Results: Asthma hospitalization rates (AHR) are expressed as cases per 1,000 child-years. Overall AHR was 2.04 (95% CI: 1.95-2.13). The annual AHR varied little (P=0.21) from 1991 (1.90) to 1995 (2.31), whereas the severe AHR rose 270%--from 0.57 to 1.55 (P < 0.001) over this period. Simultaneously, the mild AHR decreased from 0.26 to 0.12. As a proportion of all asthma hospitalizations between 1991 and 1995, severe cases increased from 31.5% to 60.3%, and mild cases decreased from 14.1% to 4.7%. Conclusions: Severity increased significantly among children hospitalized for asthma while the overall asthma hospitalization rate remained unchanged. A substantial increase in the severity threshold for admission appears to be the most likely explanation. Figure

figure 1

Figure 1