ABSTRACT
As discussed elsewhere, a normal individual who gets adequate sleep should be able to maintain wakefulness during the day with little to no difficulty. When such an individual consistently falls asleep if not actively stimulated or in passive situations (watching television, reading, at the theatre, driving), this probably represents a clinical problem. It should, however, be distinguished from fatigue, which is seen in many medical and psychological disorders. People with true hypersomnolence, as opposed to fatigue, often fall asleep unintentionally. Tired people, on the other hand, complain about ‘exhaustion’ and ‘lack of energy’ rather than about falling asleep unintentionally. Minimal research, however, has been done on this ‘language of sleepiness’, and so much of what we know about this subject is based on clinical experience alone. When history cannot confidently help to distinguish fatigue from sleepiness, a Multiple Sleep Latency Test (MSLT) is indicated.
