Seasonal variation in asthma-related hospital and intensive care unit admissions

Seasonal trends in asthma-related hospitalizations are widely recognized; however, little is known about trends in asthma-related intensive care unit (ICU) admission-, or intubations. The objective of this study is to examine monthly rates of asthma-related ICU admissions and/or intubations as a percent of total asthma-related admissions and to identify seasonality. This analysis was performed in a database of 285 hospitals representing >3 million annual inpatient visits. Asthma-related hospital admissions for patients aged 5 and older were identified with a primary diagnosis of asthma (493.xx) during calendar years 2001-2002. The percents of the total admissions per month were compared. Monthly means were calculated and data were presented as moving averages. A total of 76,916 hospital admissions were identified with a primary diagnosis of asthma. Just over 10% (n = 7,903) were admitted to the ICU and/or intubated, with the majority among patients >35 years of age (>70%). A peak in asthma-related hospitalizations occurred in the winter months (10.3%) and a nadir in the summer months (5.9%; p < 0.004) with similar trends for ICU admissions. Despite this finding, ICU admissions and intubations remained relatively constant as a percent of total asthma-related hospitalizations, ranging from 9.2 to 10.9% and did not dip during the summer months when the overall asthma-related hospitalization rates were lowest. Significant differences in seasonal variation were also noted by age group and by region, but not by gender. These findings suggest a need for year-round vigilance and improved compliance with asthma therapy, especially during the summer when asthma attacks are perceived to be infrequent.