Introduction

A recent telephone survey of 1125 adolescents aged 15-18 from France, Great Britain, Germany, and Italy found that about 20% were sleepy in the daytime, 25% had insomnia symptoms, and 4% met established criteria for an insomnia disorder.1 2 Sleep-wake disorders are common and have an important impact on the quality of life of children, but if they are promptly recognised and treated the outcome is favourable. Alertness is the inherent ability of the brain to sustain attention and wakefulness with little or no external stimulation;3 sleepiness results from impaired daytime alertness.

Methods

To review issues pertaining to childhood sleep-wake function, we selected Cochrane reviews and key original articles pertaining to sleep neurobiology and childhood sleep-wake disorders, and used our own clinical experience in writing this review.

Mechanisms of sleep-wake regulation

Whether a person is awake or asleep at any given time depends on the net balance between the circadian drive, which facilitates wakefulness, and the homeostatic drive, which facilitates sleep.4^–6

The suprachiasmatic nucleus of the hypothalamus is the circadian timekeeper (biological clock); it receives photic input from the retina and regulates the timing and length of sleep. The hypocretin (orexin) neurons located in the dorsolateral hypothalamus, and their projections to the ventral forebrain and brainstem, serve as the major wakefulness promoting system.

Serum levels of melatonin, a sleep inducing hormone produced by the pineal gland, rise just before sleep onset. Around adolescence, the timing of release of melatonin shifts to a later time at night, rendering teenagers incapable of falling asleep before about 10 30 pm.

Recognising childhood daytime sleepiness

As a general rule in a school age child, habitually falling asleep while travelling in a car or train for less than 30 minutes or while reading or watching television, or regularly napping on return home from school in the afternoon should raise …