Circadian differences among 4,096 emergency department patients with acute asthma

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In patients with asthma, airways narrow during the night. The clinical implications of a nocturnal presentation of patients with acute asthma to the emergency department (ED) are uncertain.


Our objective was to determine whether patients with asthma who had ED visits during the night (midnight to 7:59 am) vs. other times were more severe, responded less well to ED therapy, and had worse clinical outcomes.

Design and Setting

We performed a cohort study, as part of the Multicenter Airway Research Collaboration (n = 77 sites). ED patients with acute asthma, ages 2–54 yrs, underwent a structured interview in the ED. Chart review of missed/refusal patients created a truly consecutive case series.

Measurements and Main Results

Among 1,602 children, 19% presented at night. Nighttime patients were more likely to be younger, male, and have a shorter duration of symptoms; there were no other clinical differences noted. Among 2,494 adults, 20% presented at night, and they were more likely to be female and to have a history of steroid use for asthma. Nighttime adults also had a shorter duration of symptoms and slightly lower peak flows (mean, 45% vs. 49% of predicted;p = .006) and were more likely to receive steroids. They were more likely to be intubated (2.0% vs. 0.2%;p < .001), but, overall, they were equally likely to be admitted or relapse after ED discharge. In contrast to objective measures of acute asthma severity, both nighttime children and adults were significantly less likely to report their asthma symptoms as severe.


Except for endotracheal intubation (in adults only), circadian differences minimally affect ED presentation, therapy, or the outcomes of acute asthma. Nighttime asthmatics may be relatively insensitive to the symptoms of severe asthma.

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