Day-time drowsiness.

Persistent or periodic day-time drowsiness is an important cause of poor work, under-achievement, and social disaster. Somnolence may be associated with anxiety, ill-health, and poor or inadequate night-sleep, but also results from a group of sleep disorders including idiopathic hypersomnolence and sleep apnoea. Idiopathic hypersomnolence seems to be a genetic disorder of non-rapid-eye-movement sleep and is distinct from narcolepsy which is a disorder of rapid-eye-movement sleep. Day-time sleepiness in sleep apnoea is probably due to inadequate night sleep. The diagnosis of these disorders depends largely on the history. Treatment of hypersomnia with central stimulant drugs is often unsatisfactory, particularly in the elderly, and tracheostomy rather than medical treatment is sometimes essential in sleep apnoea.