What are sleep disorders?

Any disorder of sleep affecting our night’s sleep or that of others.

Causes of daytime sleepiness, snoring and obstructive sleep apnoea

There is a spectrum of disorders ranging from occasionally irritating snoring, caused by colds, hayfever or alcohol, to loud snoring with obstructive episodes (Apnoeas) disrupting sleep up to many hundreds of times per night.

Simple snoring usually affects the sleeping partner but as it becomes more severe, it begins to affect the sleep of the snorer.

Obstructive Sleep Apnoea may disturb the partner and frighten them but above all the disruption of sleep causes daytime sleepiness. This sleepiness can be estimated by means of a simple scoring system called ‘The Epworth Sleepiness Scale’ (This scoring system assumes a regular sleep time of seven to eight hours. (See note below on Inadequate Sleep Time):

Diagnosis of Sleep Apnoea is by a simple respiratory Sleep Study.

Periodic limb movement

In this condition the sufferer makes a jerking movement of the legs or body every 30-60 seconds whilst asleep. This movement may disturb the partner and also cause a brief disruption to the sleep pattern resulting in daytime sleepiness. Again a Sleep Study will show this.


This is a disorder characterised by almost irresistible daytime sleepiness.

Features of Narcolepsy:

  • Cataplexy – Episodes of sudden muscular weakness leading to collapse or limpness of limbs. This is often precipitated by emotion such as laughing, crying or shock.
  • Hypnagogic Hallucinations – Vivid like dreams at onset of sleep, (not during).
  • Sleep Paralysis – The sensation of being unable to move when waking which may last for a few seconds to several minutes.

Narcoleptics may derive some benefit from a short nap, which leaves them feeling refreshed.

Narcolepsy may start in adolescence or early adulthood but the full group of features may take many years to develop.

Inadequate sleep time

Probably the most common cause of daytime sleepiness and increasingly important in our 24/7 society. The average adult requires between seven and nine hours sleep per night. Demands of work, family and social life may erode this but a regular shortfall will affect our lives and health significantly.

Shift workers often sleep inadequately because they are trying to sleep when the rest of the family is active.

If you suffer from daytime sleepiness, a good starting point is to complete a Sleep Diary for a couple of weeks.

If the average sleep time is significantly less than eight hours, then this should be addressed by lifestyle changes. As set out in our Sleep Hygiene advice sheet: