Abstract

Nocturnal cough and wheeze are common in asthma. The cause of nocturnal asthma is unknown and there is conflicting evidence on whether sleep is a factor. Twelve adult asthmatic subjects with nocturnal wheeze were studied on two occasions: on one night subjects were allowed to sleep and on the other they were kept awake all night, wakefulness being confirmed by electroencephalogram. Every patient developed bronchoconstriction overnight both on the asleep night, when peak expiratory flow (PEF) fell from a mean (SE) of 418 (40) 1 min-1 at 10 pm to 270 (46) 1 min-1 in the morning, and on the awake night (PEF 10 pm 465 (43), morning 371 (43) 1 min-1). The morning values of PEF were, however, higher (p less than 0.1) after the awake night and both the absolute and the percentage overnight falls in PEF were greater when the patients slept (asleep night 38% (6%), awake night 20% (4%); p less than 0.01). This study suggests that sleep is an important factor in determining overnight bronchoconstriction in patients with nocturnal asthma.