aetiology

Last edited 04/2020

The causes of excessive daytime sleepiness may be divided into:

• insufficient quantity of sleep
• probably the most common cause of EDS
  • a common extrinsic cause of insufficient sleep is lack of time because of work or social pressures
  • however, most people make up for insufficient sleep during weekends or holidays
  • insomnia, owing to an intrinsic hyperarousal state that affects sleep onset and maintenance, is the commonest cause of insufficient sleep
• poor quality of sleep
• poor sleep (quality) can be classified as caused by extrinsic or intrinsic factors
• sleep disturbance caused by extrinsic environmental noise, light, or medical disorders causing pain and discomfort is usually obvious
• intrinsic sleep disorders—obstructive sleep apnoea and periodic limb movement syndrome—are common causes of disturbed sleep
• these patients typically report sleeping for enough duration (eight hours or more) but their sleep is disturbed by recurrent arousals from obstructed breathing and leg kicking, respectively
  
• unwanted drug effects
• primary neurological disorders
• narcolepsy, idiopathic hypersomnia, and circadian rhythm disorders are the main intrinsic neurological disorders affecting the sleep wakefulness centre in the hypothalamus

Reference:

• Drug and Therapeutics Bulletin (2004); 42(7):52-6.
• Brown J, Makker KM. An approach to excessive daytime sleepiness in adults. BMJ 2020;368:m1047