61. Questions and answers about Non-24

17 February 2011 at 13:56 | Posted in Circadian rhythm | 18 Comments
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About 50% of the totally blind have Non-24-hour Sleep-Wake Cycle Disorder while it is very rare among sighted people.  People with Non-24 cannot adjust to the environmental 24-hour cycle.

If Hayakawa et al. are to be believed, there have been only 96 cases of N24 in sighted people reported in studies, worldwide, ever.  The first 39 were reported in 26 separate studies dated 1970-2003.  Hayakawa’s group reported on 57 cases in a report in 2005*.  These 57 were diagnosed in Japan in 1991-2001.  So what have I learned from that paper?

Are there equally many men and women?  No, there are more than two and a half times as many men.

Is Non-24 about as common as the other Circadian Rhythm Disorders (CRDs)?  No, the other CRDs together, primarily DSPS, are six times as common.

Do people with Non-24 have anything else in common physically?  No.  Eye examinations, blood counts, serum biochemistry, electrocardiography, electroencephalography and brain MRIs show nothing special.

Socially?  89% were unmarried and 39% were unemployed.

Had they any health problems in common before the onset of free-running?  28% had psychiatric problems (obsessive-compulsive, adjustment, schizoprenia, anxiety or depression and often associated social withdrawal), not remarkably higher than the general population.  But more than a fourth had DSPS before developing Non-24.

How old were they at the onset of Non-24?  86% were ten to twenty-nine years old, none younger than ten.  Sex had no effect on the age of onset.  (None of the subjects was over 50.)

Do the hours of sleep correlate to the length of the endogenous circadian cycle?  Most of the subjects’ cycles were between 24.5 and 25.5 hours, with only one having a cycle longer than 26.5 hours.  Subjects slept between less than 7 hours to more than 12, with the majority sleeping 9-11 hours.  But there was no correlation between the period of the sleep-wake cycle and sleep length, and neither was affected by sex nor employment status.

How debilitating is the disorder?  “98% had a history of disturbed social functioning due to inability to regularly attend school or work.”

Do people with Non-24 often develop psychiatric problems after the onset of the disorder.  Yes, but depression only, not the other disorders.  “It is possible that these patients had tried to adapt themselves to their social life and failed, leading to psychological stresses that could have precipitated their depression.”

How does Non-24 in sighted people differ from that of people who are blind?  The blind generally have a shorter circadian period, and it doesn’t fluctuate over time.  In sighted people, the period tends to be longer when sleep onset is in the daytime than when a person falls asleep during nighttime.

*Tatsuro Hayakawa, Makoto Uchiyama, Yuichi Kamei et al.  Clinical Analyses of Sighted Patients with Non-24-Hour Sleep-Wake Syndrome: A Study of 57 Consecutively Diagnosed Cases.   SLEEP 2005;28(8):945-952


Next post:  62.  Psychiatric misdiagnosis of N24



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  1. I’m surprised that this condition is so rare. It is one of the reasons that I have given up on trying to find acceptance or a cure – but instead I believe the best course of action is to maintain as high a quality of life as I can, out of synch with the rest of the world.

  2. What is a rare disease? According to Wikipedia, “The definitions used in the medical literature and by national health plans are … divided, with definitions ranging from 1/1,000 to 1/200,000.” My rusty math puts the prevalence of Non-24 at 1/4000. Studies in the 1990’s gave about 0.15% prevalence for DSPS. According to the above paper, DSPS is 6 times more common than Non-24. That makes 6 in 4000 for DSPS and 1 in 4000 for Non-24.
    But I digress. It sounds like your attitude may make the disorder less stressful than it is for some. It must be isolating. Thanks for commenting.

  3. This is very interesting. Thanks for putting all this information here. I can see many ways that my own Non-24 family member fits this picture, varied as it is. I hope they keep studying it and find out more and more as we go along.

  4. Thanks for commenting, Frances. They do keep on studying and finding out things. But there’s no sign yet of any effective treatment 😦

  5. Great post! I just finally saw a sleep specialist yesterday and am scheduled to have a polysomnogram and MLST in a little over a week. My doctor suggested non-24 due to my erratic sleep patterns among other things. It’s really astonishing to see how rare the disorder is, but nice to know that I’m not the only one out there with the problems. Thanks for sharing!

  6. Thanks for commenting, NeedsMoreSleep! It’s great for you that you have a doctor who’s actually heard of Non-24 — that’s a vital first step toward diagnosis! The polysomnogram is mainly to rule out other disorders, right? A sleep diary is a major tool in diagnosing circadian rhythm sleep disorders. An exciting time for you – learning that you’re not the only one and looking forward to that test. Good luck!

  7. Thanks so much! Once I got home and really started doing my research, I realized how surprising it was that my doctor came up with non-24 with no prompting at all.

  8. “there are more than two and a half times as many men.”

    I’m wondering . . .

    Considering that N24 is very rare, thus it is difficult to get diagnosis and treatment …
    And considering that, for good or for ill, developed societies still tend to put heavier expectations on men as far as being the “bread-winner” goes …

    Couldn’t the impression that there are 2.5 times as many men with N24 than women be an artifact of who seeks treatment rather than who has the condition?

    Compare depression. For a long time, it was believed that women were more susceptible than men to depression. Then some researcher realized that what was really happening was that women were more likely than men to report their depression to a doctor and seek treatment (probably due to gender-related social stigmas.)

    So … wouldn’t a man — who has extra social pressure to be successful in his career so that he can support a family and who has extra social stigma surrounding being unable to work for any reason but particularly due to an invisible disability that others don’t understand well or often even don’t accept as real — have more pressure to seek treatment?

    And wouldn’t a woman — who may have children to support and may have stigma attached to not working but who faces less social stigma than a man if she chooses to live with her parents into adulthood and who is more likely to have a spouse who accepts the condition and shelters and protects her regardless than a man is likely to have a spouse willing to do the same for him in such a circumstance — be more likely to try to learn how to live around it than to go through the struggles of getting a diagnosis and treatment?

    Maybe I’m wrong and maybe the differential in societal pressures on the genders and societal acceptance of certain behaviors from the genders has nothing to do with the skew in diagnosis.

    But it’s certainly something to think about. At least I think it is.

  9. Interesting thoughts. Since the paper is based on only 96 patients, it may not represent the final answer on any factor. Over half of the people are/were Japanese, and in that ordered society your comments about societal pressures may be even more valid than in the West (?). But “more than 2 1/2 times as many” is a lot and societal pressures may not account for all of that skew.

  10. One aspect of Japanese culture that I have long found interesting is the tendency of families to hide their ill, especially those with mental illnesses or conditions that might be perceived as mental illness, because having someone like that in the family is a source of shame and dishonor.
    So I would expect there to be even more people (both male and female) with N24 in Japan who are being shielded by their family and hidden from public view, including a viewing that might include treatment.
    Along these lines, there’s a special word in Japanese — hikikomori — for young adults who have a breakdown from the stress of school and social life and retreat to hide in their room for years, decades, or even the rest of their life . . . usually without any kind of psychological treatment to help put them back into society. (and, interestingly, while researchers claim that it appears that there are equal numbers of male and female hikikomori, it is predominantly males who are reported, studied, and treated.)
    So, yes, definitely, Japanese reporting on something with such high potential for stigma as N24 is likely to be quite skewed.

  11. Re. 2.5 times as many males with n24 might be related to genes or alleles located on the X or Y chromosomes. I know that polymorphisms in the gene that transcribes the 5-HT2c receptor are expressed differently in males due to the lack of an allele on the Y chromosome. Are there more Male N24s responding to the “nite-owl” list? or this blog?

  12. A quick off topic-question. I’ve been N24 for the last 7 years, (yet I just stumbled across this blog a week or so ago) and was probably DSPS before that for as long as I can remember. Most of the comments from other DSPS/N24 people seem to imply that if left to their own devices (ie. sleep and wake when they want) that they feel good (ie. rested, awake, alert, energetic) and that they mainly feel poor when attempting to constrain their rhythm. In my case I feed poor (worn out, tired, foggy head/unable to concentrate, ect…) all the time regardless of when I sleep or wake, its just near impossible for me to adjust my schedule otherwise. Is this an accurate observation? Do you guys feel good when allowed to sleep/wake as you please? That’s one thing I feel seems to be overlooked is that when discussing various therapies/strategies/ect… is the focus is always on its effectiveness, and rarely is ‘quality of life’ mentioned. Perhaps its implied that a successful therapy includes a good quality of life? Any thoughts?

  13. Ryan, I am glad you asked that. I have much the same problem as you do. I feel chronically tired, worn out, and foggy almost every day, no matter what schedule I am on. As you point out this is not true of all N24s. Some feel fine on their own schedule. But not me. My fogginess is especially prominent early in my “day” — no matter when that day is by clock time — and over the course of the time I am awake it gradually improves. But only very late in the day to I ever feel clear headed and energetic and that is only on a good day and for a few hours at most. Most of the time I feel like my mind is foggy and my energy is low.

    There was a time when I was able to treat my N24 with light and dark therapy. That no longer seems to work for me. But even when it did work, all it did was keep my sleep on a 24 hour schedule. It did not relieve the constant tiredness.

    I think in my case the rhythm of tiredness is what drives the N24 rather than the other way around. I am so tired early in the day it prevents me from getting going. And then later in the day when I should be about to sleep I get a brief burst of energy which then keeps me from going to sleep. Sometimes this energy is very stimulating and I tend to pace or walk or even run. But this is only for a very short period and not every day. 90% of the time I am in a state of tiredness.

    My tiredness was actually confirmed by a lab test (the multiple sleep latency test) which showed that I was abnormally sleepy even when I was — according to my own rhythm — supposed to be awake.

  14. I find it interesting that ‘light box’ therapy is used in treating this condition, however; I think the ‘light boxes’ I stare at all day (computer screen) or evening (iphone, tv) are part of the cause. I wonder what pattern of sleep I would have had 200 years ago.

  15. Thanks for putting this up, it’s really helpful. I’ve been searching for more information on this disorder the last years. I’m actually one of those that feel good and energic most of the day as long as I keep my own rythm. My main problem is that I follow a lot of sports on tv and I have to stay up for them, which often results in very little sleep in some periods, making me almost apathetic most of the time.

    Anyway, it’s great to see there’s more people out there in the same boat as myself. One thing I have learned by having this disorder is not to care about what society or anyone else thinks of me. Many will call us lazy, stupid and other things because they don’t understand the seriousness of the disorder. I simply cannot keep a steady sleep cycle.

  16. Wow. the 28 Nov. 2011 comment by “L” sounds so much like me, it’s startling.

  17. That’s very interesting NorrinRadd. So you also are in a foggy state most of the day but only get some energy late in the day when it is time to go to sleep?

  18. Happy Belated Thanksgiving.
    I am grateful for YOU and for this site.
    By way of acknowledgment for ALL you do for the Circadian Sleep Disorders community, this article is linked as Related Content on my 11/29/13 “Motivation and Gratitude” article on ADDandSoMuchMore.
    Check it out when you have a moment.



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