Circadian Rhythm Sleep Disorders

Circadian Rhythm Sleep Disorders


I’m sure all of us have pulled our late nights or all-nighters at least once in our lives, at least I have. If you have too, then you can imagine how much of a tool that takes on a person, to not sleep on that designated time our body feels the need to rest. How is this possible, how is it that our body knows exactly when to sleep and doesn’t mess up the timing? Our body has a 24-hour “internal clock.” This internal clock helps us fall asleep at the right time of the day and it is called a circadian rhythm. Circadian rhythms are found in all living organisms and nearly all of our physiological functions, most importantly our sleep and wake cycle, depend on our circadian rhythms. Now, when a person’s internal clock faces difficulties identifying the time to sleep it may cause a great difficulty for the person. The person may wake up quite frequently when they are sleeping, they may face issues falling asleep on time or may stay awake at odd hours. What is this phenomenon? It’s called the Circadian rhythm sleep disorder. 



CRSDs usually manifest from a chronic or recurrent disturbed sleep-wake pattern which may result because of a dysfunction of the circadian clock system, or a skew between the timing of the body’s internal clock and the externally enforced social and work cycles. All of this can result in significant functional impairments. CRSDs can be classified according to their suggested underlying causes: 1) the internal clock itself has varied due to maybe delayed sleep phase disorder, irregular sleep wake rhythm, advanced sleep phase disorder; 2) the outside environment or social circumstances have altered the circadian clock (jet lag, continuous late shifts at work). 



A patient’s history of sleep-wake pattern helps in the diagnosis of a CRSD. Some diagnostic tools are also used namely a sleep diary and actigraphy. Actigraphy watches are usually worn on the non-dominant wrist for at least 7 to 14 days for the rest and activity patterns of an individual to be recorded. Melatonin rhythm and body temperature are dependable biological markers of the internal clock. Regulated by the Suprachiasmatic Nucleus (SCN), and in dim light, the pineal gland secretes melatonin at about 2 to 2.5 hours before the onset of sleep. The treatment and management of CRSD necessitates an eclectic approach because biological, environmental, and behavioural factors all can be instrumental in the manifestation and severity of the symptoms. 



I will be mentioning some common types of  CRSDs, firstly we’ve got Delayed Sleep Phase Disorder (DSPD) is a sleep disorder where there is a consistent delay of the major sleep episode compared to the normal sleep-wake cycle. This steady delayed pattern leads to symptoms of insomnia and excessive sleepiness during the day which can impair daytime functioning. For its treatment, making use of behavioural techniques can help, manipulation of light/dark exposure, and in some, pharmacological help can also be used. 



Advanced Sleep Phase Disorder (ASPD) is a sleep disorder characterised by a stable advancement of the major sleep period, it involves a habitual and involuntary sleep onset and wake-up times which are distinctly hours before the desired and typical clock time. Exposure to bright light timed for 2 hours in the evening, planning sleep-wake schedule and adhering to proper sleep hygiene is all recommended to treat this condition. While hypnotic agents can also prove to be useful for ASPD, it is not approved by the FDA. 



Non-24 Hour Sleep Wake Disorder (N24HSWD) also known as Free-Running Disorder among other things is typically characterised by chronic or recurring sleep-wake patterns which are not synchronised with the 24-hour environmental cycle. Individuals gradually shift to later and later times of sleep onsets and wake times. The initial approach prefers for an individual to have good sleep hygiene, a structured social, school and work schedules and a low dosage of melatonin one hour before their preferred sleep time. 




Conditions that affect this sleep are:


  • light

  • the physical activity a person is doing

  • the social activities that a person is involved in

  • The level of melatonin in the body



These factors are also presented individually or in combination with each other. 


Risk factor


Certain diseases like heart failure or Chronic Obstructive pulmonary disease are more likely to experience this disorder. Some additional factors are: 



  • Some chronic pain syndromes

  • Hyperthyroidism

  • Intellectual disability

  • Dementia



These were some of the CRSDs and their basic treatment approaches. Given how important circadian rhythms are for our better functioning, the challenge lying ahead of researchers and people treating these disorders is to develop more precise clinical treatment and practical diagnostic tools for all the different CRSDs. 



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