What are Circadian Rhythm Sleep Disorders?

Circadian rhythm clock

Circadian rhythm sleep disorders are due to disruptions in the circadian rhythm otherwise known as your body?s internal clock. The circadian rhythm controls your body processes on a 24-hour recurring cycle. The word circadian has a Latin root, ?circa? means around or approximately and ?diem? which means day. So the literal meaning is “around the day.”

The main characteristic of circadian rhythm disorders is a disruption of regular sleeping time. This disruption can have two main causes, either your internal body clock isn?t functioning normally or the internal body clock and the real world time are out of sync, which affects how long you sleep and what time you actually fall asleep. Resulting from this mismatch in the circadian rhythm, persons with CRSDs (Circadian Rhythm Disorders) often appear to suffer either from insomnia or feeling sleepy during the day, which negatively affects their social life and school or work performance. Note however that persons with CRSDs oftentimes sleep for normal periods of time (7-9 hours) if allowed to follow their body clocks, so these specific disorders do not influence how long an individual will sleep.

Types of Circadian Rhythm Disorders

Circadian Rhythm Sleep Disorders (CRSD) can be categorized into six (6) distinct types (using the International Classification of Diseases): Non-24-Hour Sleep-Wake Phase Disorder, Jet Lag, Shift Work Sleep Disorder, Delayed Sleep Phase Syndrome, Advanced Sleep Phase Syndrome, and Irregular Sleep-Wake Rhythm. These can also be divided into two supercategories – extrinsic and intrinsic types.

Extrinsic CRSDs are those in which the disorder is brought on by an alteration in sleep timing by virtue of circumstances. Shift work sleep disorder is the primary candidate in this group, as is jet lag. All other CRSDs are of the intrinsic type, ie. they are based on the individual?s specific makeup. We?ll cover the extrinsic types first and then the intrinsic.


Jet Lag
red eye flight

Don’t you just HATE those red-eye flights?

Jet lag is probably the most well-known CRSD and can be quickly overcome by simply returning to a normalized sleep schedule. When a traveler passes from one timezone to another, the change in light and normal sleep schedule signals can create temporary CRSD. Jet Lag manifests when the pattern of sleep and wakefulness is affected because of a new time zone, so it is hard for people to adjust and have good performance in the new time zone. This not to say that one?s cycle will not adjust, it eventually will but very slowly?usually not more than 1 or 2 hours per day. This is why it is sometimes said that the number of days required to shift is equal to the time zone difference in hours. When I went to India (10+ hours ahead of Jamaica), it took me a little more than a week for my sleep cycle to catch up!

Beating this type of CRSD is really a matter of effective preparation. Travelling West-to-East is usually more difficult because of the shortened daylight exposure, but in the opposite direction it?s much easier since you?d only be coping with a longer day. It is advisable to discover the hourly shift between your primary timezone and your target, and commence shifting your sleeping time at least a full two (2) days before. After landing, be sure to stick to your normal routine against the new time zone to rapidly cement any changes and decrease your chances of extended jet lag.

Shift Work Sleep Disorder
the graveyard shift

Really not a fun time to be at work…

Shift Work Sleep Disorder is a common problem in people who rotate shifts or work at night. Work schedules affect the body’s circadian rhythm and some people find it difficult to adjust to the change. This causes interruptions in the pattern of sleep like insomnia or excessive sleepiness, so they can’t get a good night’s sleep. Most shifts will align with the 8-hour or 12-hour work period depending on what the employer deems as best aligning with their environment or service delivery strategy.

You will also find that shifts may either be static or rotating with varied effects on those that work them. For example, in my case, I worked on monthly rotations. This was pretty bad because once I started adjusting to a specific rhythm, I would then be placed on another shift which would immediately trigger further adjustments once more. It is pretty interesting that rapidly rotating shifts clockwise (usually every 3 days) may actually be better because they do not allow time for the Circadian rhythm to be thrown out of synch significantly. Needless to say, persons in their 20s or 30s are more suited for this kind of thing, than older people (who become more ?morning persons? as they age).

Once more, dealing with shift work is a matter of timing?adjusting one?s sleep cycle in advance of a new rotation. This can mean going to bed 1 or 2 hours later (if on a clockwise schedule) a few days before transitioning so as to ease into the new working period. The main shift that people tend to have issues with is the?you guessed it?night or ?graveyard? shift. This tends to be the worst because it goes directly against your body?s need to sleep, and then the light of the morning sun only serves to trigger wakefulness in workers heading home. Light therapy is a great way to help fend off sleepiness before heading into a night shift, with 15-20 minute napping breaks taken to restore alertness. It?s also important to make sure that the environment at home is conducive to sleep: dark, cool, and with very little ambient noise.

Intrinsic CRSDs

Delayed Sleep Phase Syndrome

Light therapy is a pretty good fix for DSP and ASP!

Delayed sleep phase syndrome (DSPS) is typified by the postponement of sleep onset to a much later than what could be considered normal. These persons are frequently known as “night owls” or may refer to themselves as “not morning people” (I know a bit more than I should about this, especially during my teen years!). As mentioned before, if they can fall asleep for a full 7-9 hours, they will feel rested. However, since these people tend to go to bed oftentimes between 2:00am and 4:00am in the morning, waking up towards the afternoon, this puts them out of sync with the rest of society from a working day perspective. Since they must also force themselves to realign with job/social perspectives, they usually do not get the necessary amount of sleep which can result in relationship problems, job loss and even development of complicated health issues.

What makes this condition complex is that the circadian rhythm is altered regardless of behaviour. Though some may say it?s a matter of discipline, that is not the case with persons affected by this disorder. Their rhythms constantly push them towards a later bed time, for reasons which are unclear at this time. Recall that the normal free-running circadian rhythm (ie. in the absence of a light-dark cycle) has an average range of 24.2 to 24.5 hours. It is perhaps possible then that persons afflicted by the condition may have a decreased sensitivity to light/darkness, since their rhythms shift without regard for external stimuli. Chronotherapy, and light therapy are recommended in this case, along with a sleep aid such as melatonin (usually before the desired bedtime) to help persons shift to a more regular cycle. This requires careful monitoring and management but helps to alleviate the feelings of grogginess and decreased performance that attend with the disorder.

Advanced Sleep Phase Syndrome

Advanced Sleep Phase Syndrome (ASPS) could be considered the opposite of DSPS, though it is less common. It tends to affect the elderly, unlike DSPS which is more prevalent in adolescents. The condition is noted by sleep onset which occurs fairly early, oftentimes around 8:00pm in the night with the individual awakening between 4am and 5am the following morning. As with DSPS, their sleep architecture is perfectly normal if accommodated. Treatment is fairly similar to DSPS as well, with the exception that chronotherapy?s use case isn?t as viable.

Non-24-Hour Sleep-Wake Phase Disorder
Teen with irregular sleep

Definitely not looking forward to the next few weeks…

Non-24-Hour Sleep-Wake Phase Disorder (Non-24) is fairly tricky condition to deal with. Like other CRSDs it tends to be misdiagnosed as insomnia, but one which is cyclical. This is due to the fact that persons having this condition seem to be on a free-running circadian rhythm. As was mentioned before, the circadian rhythm is not perfectly aligned to a 24-hour day, which is why the light-dark cycle is important in resetting it. Without a zeitgeber (?time giver?), the cycle will run its maximum length, which means persons could go to sleep anywhere between 30 minutes to 1 hour later each day.

Why does this happen? The reason yet again isn?t fully clear, but we do know that for some reason light either does not reach the SCN or the individual does not show the same level of sensitivity to its presence. Obviously this is a great problem for the visually impaired, specifically for those who are totally blind. In the final analysis, they will have cycles of good sleep intermixed with poor sleep since their rhythms are not being reset. Like ASP/DSP, phototherapy can be used to help reset the cycle, although this is more effective in sighted individuals. Medication and sleep aids such as melatonin is a solution for both the visually impaired and those that are able to see.

Irregular Sleep-Wake Disorder

ISWD can be really hard, especially on the elderly.

Irregular Sleep-Wake Disorder (ISWD) is characterised by the inability of an individual to maintain a single contiguous block of sleep, instead napping throughout the day and night. When you sum the duration for all naps, you may be surprised to find that the total time spent asleep may be normal for the individual?s age. Despite this, persons with this condition are frequently sleepy during the day and awake for long periods at night. Though rare, it can be very debilitating, and can affect a person?s ability to maintain social and familial relationships, eventually leading to possible isolation.

You will find that this condition tends to occur in persons with dementia, Alzheimer?s disease and/or mental retardation. Persons without neurological issues can also express it as well so there?s no hard and fast rule about onset. Treatment can be fairly complex, since not all persons with neurological disorders may respond well to all interventions. Light therapy can be used in most cases, but medication will depend on what prevailing conditions exist with the patient. It is important to get the individual to have largely continguous sleep and wake periods so that they can regularise their cycles. Following a proper sleep schedule with good sleep hygiene can also assist in this endeavour.

CRSDs are both complicated and interesting health phenomena. The individuals affected by the conditions may experience very few problems (such as with jet lag) up to a multitude of other issues (such as those associated with the intrinsic CRSDs).In all things it is important to be aware of the treatments available, taking into account the use of phototherapy and sleep aids to assist with getting things back on track.

I do hope you found this to be informative. Please drop me a line below for more information and feel free to share!

Sleep well until next time,



  1. Jenna Fox

    Hi Joshua,

    Thanks for writing this post on circadian rhythm sleep disorders. I had no idea there are so many different types of sleep disorders! I just came back from my honeymoon in Thailand and I definitely experienced jet lag. It took me quite awhile to recover from it.

    I’m also interested in the irregular sleep-wake disorder because I think my mom exhibits signs of it. You mention light therapy can be used to correct it, can you expand on that? What kind of therapy?


    1. Joshua (Post author)

      Hey Jenna, glad you found this informative.

      In a nutshell, bright light therapy involves sitting with a light box, lamp or simulator for a specified amount of time. The device, whichever is used, provides artificial light which triggers a reset of our internal body clock. This promotes wakefulness and can help users get on to a regular sleep schedule. In the case of irregular sleep-wake disorder, the aim is to get the user to stay awake as long as is possible during the day, so that their sleep at night is continuous, rather than fragmented.

      Insofar as your mom is concerned, it may be good to keep a sleep journal so as to record what’s happening with her. When doing so, please make a list of any other prevailing conditions she might have. This will give a physician the information necessary to plan for any additional therapies or treatments so as to give your mom the best help possible. Please let me know how it goes!

  2. 3esso

    Thanks Josh for this comprehensive and detailed review.
    I think that the long working hours and the lack of rest are a major cause of sleeping hours. People these days work at least two jobs in order to support themselves financially.
    I myself wake up everyday at about 5:30 am to go to work, to return home ay about 11pm, and I never go to bed before 12 am.
    I got used to this lifestyle, I admit that I feel tired most of the time and I fel asleep a couple of times while driving (thanks God I didn’t do an accident ), but I got used to this that even in the holidays I find myself waking up early as well.
    I don’t know if this means that I am suffering from a certain disease or what.
    Thanks again and looking forward to more valuable articles from you.

    1. Joshua (Post author)

      Hey 3esso, you’ve got to be careful. You don’t appear to have a disorder, but you are building up a continuous sleep debt since you’re getting less than the 7-9 hours of sleep recommended per night. That can have many ill effects…including high blood pressure, heart disease and even diabetes. Since you’ve made it routine, you will naturally wake up early, but I can see that’s a consequence of both your job(s) and any commutes necessary. It may be good to see if you can take at least two (2) 20-minute naps throughout the day to help retain your alertness…otherwise you will suffer from microsleeps…of which you may or may not be aware. Ideally though, you need to get your proper bed rest!


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