Sleep medicine is a young and rapidly evolving science. It was only in 1953 that we started to understand sleep physiology with the discovery of REM (rapid eye movement) sleep.
So it’s not surprising that the task of categorizing sleep disorders was only undertaken a few decades ago. And it’s far from a finished project. The nosology (the way disorders are classified) of sleep medicine is far from fixed.
Conditions such as sleep apnea require a physiological approach to diagnosis and treatment, whilst other disorders may require the expertise of mental health professionals.
It’s unlikely we’ll arrive at a ‘unified theory’ of sleep medicine any time soon, but for now, the standard tool used by the majority of health professionals dealing with sleep disorders is the International Classification of Sleep Disorders (ICSD).
How do you define a sleep disorder?
The first attempt to classify sleep disorders came in 1979. The Diagnostic Classification of Sleep and Arousal Disorders, published in the newly formed journal, Sleep, was largely organized into symptomatic categories ie (insomnia, hypersomnia, and abnormal events occurring whilst sleep).
However, it was difficult to make a diagnosis based on pathophysiology (quantifiable measurement) because most of the causes of sleep disorders were unknown at the time.
By 1990, knowledge had progressed sufficiently to warrant a new classification. The International Classification of Sleep Disorders (ICSD) was published by the major international sleep societies at the time, a group comprising of the American Sleep Disorders Association (ASDA), European Sleep Research Society, the Japanese Society of Sleep Research, and the Latin American Sleep Society.
The ICSD comprised 84 separate disorders based on pathophysiological concepts. In 2002, the American Academy of Sleep Medicine set up a committee to further revise the classification resulting in the current classification, the ICSD-2.
ICSD – an international standard
The ICSD-2 was published with the goal of standardizing definitions of sleep disorders and creating a systematic approach to diagnosis. It is widely used by clinicians and researchers worldwide, improving research efforts throughout the international community by adhering to a recognised set standards.The ICSD-2 outlines the following goals:
- To describe all currently recognised sleep and arousal disorders, and to base the description on scientific and clinical evidence.
- To present the sleep and arousal disorders in an overall structure that is rational and scientifically valid
- To render the sleep and arousal disorders as compatible with ICD-9 and ICD-10 as possible
- Sleep Related Breathing Disorders
- Hypersomnias of Central Origin Not Due to a Circadian Rhythm Sleep Disorder, Sleep Related Breathing Disorder or Other Cause of Disturbed Nocturnal Sleep
- Circadian Rhythm Sleep Disorders
- Sleep Related Movement Disorders
- Isolated Symptoms, Apparent Normal Variants, and Unresolved Issues
- Other Sleep Disorders
Are these definitions likely to change?
The science of sleep medicine is still an emerging field and new discoveries are being made all the time.
So whilst the ICSD-2 is the most up to date classification of sleep disorders in use today, there will no doubt be more revisions as knowledge progresses over the coming years.
Sleep medicine practitioners will have to be flexible in their approach and adapt the way they categorise, diagnose and treat sleep disorders.
|CATEGORY/SUB-CATEGORY||SLEEP DISORDER||ALTERNATIVE NAMES|
|Adjustment Insomnia||Acute insomnia, short term insomnia|
|Paradoxical Insomnia||Sleep state misperception|
|Idiopathic Insomnia||Primary insomnia|
|Insomnia Due to Mental Disorder|
|Inadequate Sleep Hygiene|
|Behavioral Insomnia of Childhood|
|Insomnia Due to Drug or Substance|
|Insomnia Due to Medical Condition|
|Insomnia Not Due to Substance or Known Physiological Condition|
|Physiological (Organic) Insomnia, Unspecified|
|SLEEP RELATED BREATHING DISORDERS|
|Central Sleep Apnea Syndromes|
|Primary Central Sleep Apnea|
|Central Sleep Apnea Due to Cheyne Stokes Breathing Pattern|
|Central Sleep Apnea Due to High-Altitude Periodic Breathing|
|Central Sleep Apnea Due to Medical Condition Not Cheyne Stokes|
|Central Sleep Apnea Due to Drug or Substance|
|Primary Sleep Apnea of Infancy (Formerly Primary Sleep Apnea of Newborn)|
|Obstructive Sleep Apnea Syndromes|
|Obstructive Sleep Apnea, Adult||OSA, sleep apnoea|
|Obstructive Sleep Apnoea, Pediatric||Child sleep apnea|
|Sleep Related Hypoventilation/Hypoxemic Syndromes|
|Sleep Related Nonobstructive Alveolar Hypoventilation, Idiopathic|
|Congenital Central Alveolar Hypoventilation Syndrome|
|Sleep Related Hypoventilation/Hypoxemia Due to Medical Condition|
|Sleep Related Hypoventilation/Hypoxemia Due to Pulmonary Parenchymal or Vascular Pathology|
|Sleep Related Hypoventilation/Hypoxemia Due to Lower Airways Obstruction|
|Sleep Related Hypoventilation/Hypoxemia Due to Neuromuscular and Chest Wall Disorders|
|Other Sleep Related Breathing Disorder|
|Sleep Apnea/Sleep Related Breathing Disorder, Unspecified|
|HYPERSOMNIAS OF CENTRAL ORIGIN|
|Narcolepsy With Cataplexy|
|Narcolepsy Without Cataplexy|
|Narcolepsy Due to Medical Condition|
|Idiopathic Hypersomnia With Long Sleep Time||Primary hypersomnia|
|Idiopathic Hypersomnia Without Long Sleep Time||Primary hypersomnia|
|Behaviorally Induced Insufficient Sleep Syndrome|
|Hypersomnia Due to Medical Condition|
|Hypersomnia Due to Drug or Substance|
|Hypersomnia Not Due to Substance or Known Physiological Condition||Nonorganic hypersomnia, NOS|
|Physiological (Organic) Hypersomnia, Unspecified||Organic hypersomnia, NOS|
|Recurrent Hypersomnia||Recurrent Hypersomnia|
|Kleine-Levin Syndrome||Sleeping beauty syndrome|
|CIRCADIAN RHYTHM SLEEP DISORDERS|
|Circadian Rhythm Sleep Disorder, Delayed Sleep Phase Type||Delayed sleep phase disorder, delayed sleep phase syndrome|
|Circadian Rhythm Sleep Disorder, Advanced Sleep Phase Type||Advanced sleep phase disorder|
|Circadian Rhythm Sleep Disorder, Irregular Sleep-Wake Type||Irregular sleep-wake rhythm|
|Circadian Rhythm Sleep Disorder, Free-Running Type||Nonentrained type|
|Circadian Rhythm Sleep Disorder, Jet Lag Type||Jet lag|
|Circadian Rhythm Sleep Disorder, Shift Work Type||Shift work disorder|
|Circadian Rhythm Sleep Disorder Due to Medical Condition|
|Other Circadian Rhythm Sleep Disorder||Circadian rhythm disorder, NOS|
|Other Circadian Rhythm Sleep Disorder Due to Drug or Substance|
|Disorders of arousal (from non-REM sleep)|
|Sleep terrors||Night Terrors|
|Parasomnias usually associated with REM sleep|
|REM sleep behavior disorder (including parasomnia overlap disorder and status dissociatus)||REM sleep disorder, RBD|
|Recurrent isolated sleep paralysis||Sleep paralysis|
|Sleep Related Dissociative Disorders|
|Sleep Enuresis||Bedwetting , nocturnal enuresis|
|Sleep Related Groaning||Catathrenia|
|Exploding Head Syndrome|
|Sleep Related Hallucinations|
|Sleep Related Eating Disorders||SRED|
|Parasomnia Due to Drug or Substance|
|Parasomnia Due to Medical Condition|
|SLEEP RELATED MOVEMENT DISORDERS|
|Restless Legs Syndrome|
|Periodic Limb Movement Disorder|
|Sleep Related Leg Cramps|
|Sleep Related Bruxism||Teeth grinding|
|Sleep Related Rhythmic Movement Disorder|
|Sleep Related Movement Disorder, Unspecified|
|Sleep Related Movement Disorder Due to Drug or Substance|
|Sleep Related Movement Disorder Due to Medical Condition|
|ISOLATED SYMPTOMS, APPARENTLY NORMAL VARIANTS AND UNRESOLVED ISSUES|
|Sleep Starts||Hypnic jerks|
|Benign Sleep Myoclonus of Infancy|
|Hypnagogic Foot Tremor and Alternating Leg Muscle Activation During Sleep|
|Propriospinal Myoclonus at Sleep Onset|
|Excessive Fragmentary Myoclonus|
|OTHER SLEEP DISORDERS|
|Other Physiological (Organic) Sleep Disorder|
|Other Sleep Disorder Not Due to Substance or Known|
|Environmental Sleep Disorder|
Jeff is the founder and editor-in-chief at Sleep Junkies . A passionate sleep advocate, he started the site in 2012, reaching millions of readers across the globe. Jeff also runs the product curation platform SleepGadgets.io . He is often asked to speak at about current trends in consumer sleep technology at various events.