67. N24 Awareness Day

24 November 2013 at 22:43 | Posted in Circadian rhythm | 8 Comments
Tags: Circadian rhythm, DSPS, Non-24, Sleep research, Suprachiasmatic nuclei

The online N24 community has decided to name November 24 as N24 Awareness Day.  We are encouraging bloggers and tweeters and anyone else with a platform to help spread awareness and knowledge of Non-24-Hour Sleep-Wake Disorder (N24).

The web page which links to these efforts is here (click on the N24 Day Logo):

This would be an appropriate time to review some events in 2013 relevant to N24.

One important advance was a paper by Kitamura et al. which measured the intrinsic circadian period in 6 patients with N24.  They compared it with two groups of individuals without a circadian disorder.  One group had an intermediate circadian preference.  The other group had an evening preference. The latter group however did not have DSPS, only a preference for being active later in the day.

Kitmura et al. found that the intrinsic period of the N24s was 24.5 hours, which was significantly longer than that of the intermediate types, but not significantly longer than that of the evening types.  The average period of the N24s was longer than that of the evening types but because of the great degree of overlap between those groups the difference was not significant.  The longest period found in an evening type subject was nearly identical to the longest period among the N24 subjects (around 24.7 hours).

These results suggest that a longer-than-average intrinsic period is a component of N24, but it is not the only causative factor.  Other factors, such as differences in phase angle between sleep and temperature rhythms, as found in several studies, may play a role.

Another paper, by An et al.  did not discuss N24 explicitly, but the results may have import for those with the condition.  They studied the effect of Vasoactive Intestinal Peptide (VIP) on shifting of circadian rhythms in mice and in cell cultures from the SCN.  They found that VIP depending on time and dose could either enhance or reduce the mutual synchronization of SCN cells.  Further, when SCN cells were less tightly synchronized together, they adapted more quickly to phase changes.  This suggests that by manipulation of VIP levels it may be possible to increase the adaptability of the SCN to phase changes.  Since N24s with a longer period need to change phase every day if they are trying to maintain a normal schedule, this approach might be of help.   It might also help people with DSPS when trying to shift to an earlier sleep phase.

–posted by LivingwithN24 (James Fadden)

REFERENCES

Kitamura S, Hida A, Enomoto M, Watanabe M, Katayose Y, Nozaki K, Aritake S, Higuchi S, Moriguchi Y, Kamei Y, Mishima K. Intrinsic circadian period of sighted patients with circadian rhythm sleep disorder, free-running type.Biol Psychiatry. 2013 Jan 1;73(1):63-9.

An S, Harang R, Meeker K, Granados-Fuentes D, Tsai CA, Mazuski C, Kim J, Doyle FJ 3rd, Petzold LR, Herzog ED. A neuropeptide speeds circadian entrainment by reducing intercellular synchrony. Proc Natl Acad Sci U S A. 2013 Nov 12;110(46):E4355-61.

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Next post:  68.  Guest post: Non-24 — Not Just a Disorder of the Blind

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