Is there a circadian variation in respiratory morbidity?

In a retrospective study of the time of presentation to an accident and emergency department patients with acute respiratory symptoms presented more commonly at night compared to a control group with abdominal pain. In a subsequent prospective study doctors from a GP deputizing service were called much more frequently at night by patients with asthma than by those with other symptoms. These findings refute the suggestion that the observed increased mortality from respiratory diseases at night results from reduced medical care as a consequence of a reluctance of patients to present during the night.