Is circadian variation in asthma severity relevant in the emergency department?

Asthmatic patients have marked circadian variation in disease severity, with bronchospasm far worse between midnight and 8 AM than at other times of day. In this study we sought to determine whether circadian variation in asthma severity is clinically relevant for purposes of emergency management.

Prospective, observational cohort study.

The emergency department of a large urban university hospital.

Asthmatic patients 16 years and older who presented with the complaint of asthma exacerbation.

Peak expiratory flow rate (PEFR), respiratory rate, and objective and subjective assessments of dyspnea severity were determined at the time of each patient's presentation to the ED and at the time of disposition decision. Time of symptom onset, duration of symptoms, response to therapy, and final disposition were recorded. Nocturnal presentation and onset were defined as arrival in the ED or onset of symptoms between midnight and 8 AM. We enrolled 188 asthmatic patients in the study; 52 (28%) presented nocturnally. Comparison of asthmatic patients who presented nocturnally and those who presented at other times revealed no differences in initial or final PEFR or respiratory rate, change in PEFR, subjective or objective dyspnea, or rate of hospitalization, although nocturnal patients did have a significantly shorter ED treatment time. Analysis by time of symptom onset also revealed no differences between nocturnally and nonnocturnally presenting subjects in disease severity or outcome, with the exception that those with nocturnal symptom onset had less subjective dyspnea than other asthmatic patients. Repeat analysis with different "nocturnal" time periods did not alter the results.

In our study group, asthmatic patients who presented nocturnally to the ED did not differ from other asthmatic patients in disease severity and therefore do not appear to represent a unique population for purposes of ED management or disposition decisions.