60. Charting the course of N2427 October 2010 at 09:25 | Posted in Circadian rhythm, DSPS, Sleep diary | 26 Comments
Tags: Circadian rhythm, DSPS, Non-24, Sleep diary, Sleep disorder
Keeping a sleep log or a sleep chart is one of the keys to getting a proper diagnosis of a circadian sleep disorder. Oftentimes someone will describe their sleep patterns, but it’s not always clear from the description when exactly they sleep. For example, someone will say they “keep going to bed later and later.” Depending on what they mean, that could either describe Non-24 Hour Sleep-Wake Cycle Disorder (N24) or a gradually worsening case of Delayed Sleep Phase Syndrome (DSPS). But a quick look at a sleep chart will usually clear up the distinction.
My eponymous co-blogger Delayed2Sleep, who has, of course, DSPS, has posted several of her sleep logs. Today I am going to post some of my sleep charts. My name is LivingwithN24 and I have, you guessed it, N24.
One thing I should note to start is that I have always charted my sleep on a vertical chart, whereas D2S has used a horizontal layout, so you’ll need to rotate the charts to compare them. I have also “double-plotted” some of my sleep charts. That means each line on the chart encompasses 48 hours. That’s a standard method in sleep studies as it helps the patterns to stand out more clearly.
These charts show a textbook case of N24. The phrase “textbook case” is not a metaphor here; the medical journal articles about my case are commonly cited in reviews of circadian sleep disorders. So there is no doubt you are looking at a case of N24 sleep. One can see that the sleep chart of an N24 shows a characteristic diagonal pattern as the bedtime and waking time slides gradually later each day. Unlike the case of DSPS, the delay does not stabilize at a particular clock time. Someone with DSPS may for example end up going to bed always around 6am for an extended period. Someone with N24 who goes to bed at 6am on Monday will likely go to bed at 7am on Tuesday, 8am on Wednesday, 9am on Thursday etc. until they have gone all the way around the clock. The delay is not always by one hour — I just chose that for simplicity. In my case I tended to delay 1.5 hours per day, meaning my “day” was actually 25.5 hours.
One can see in this chart that there is some irregularity in the sleep times, and there may also be daytime naps. Both of these showed up a lot in January and February of that year. But there is a nonetheless a clear pattern to the sleep. In some months such as March, April and May it stands out especially clearly.
It might also be of interest to compare these charts to another type of chart. In circadian medicine a technique called actigraphy is used. The patient wears a device called an actimeter on their wrist which records movement. Since people tend to move about a lot more when awake than when asleep, actigraphy can be a way of confirming the sleep times of a patient with N24 or DSPS. Here is an actigraphic chart of my sleep from around the same time as the sleep logs. The difference is the black squiggles on the actigraphic chart show time awake, rather than asleep, but the same diagonal pattern is present.
Now those charts are from 1991. The readers of this blog are clever folks and have no doubt noticed it is now 2010. I did this for a reason. Most of the studies of N24 have looked the subjects at one point in their lives. Few, if any, have examined how the sleep patterns of N24 change over the course of many years. I have noticed a number of changes in my sleep between 1991 and today.
One thing I noticed is that it is much more difficult to control my N24 with lights, darkness and sleeping medications. In fact, over this summer it became impossible. So in September I stopped using the lightbox and the sleeping pills to see what my sleep would do on my own.
Here is a sleep chart I made for the last 5 weeks (Sept 18-Oct 25, 2010). Instead of making the chart by hand I used the SleepChart program from supermemo.com.
This is quite different from the 1991 charts. While there is still a recognizable diagonal drift of the sleep times, it is much more erratic. The times of sleep are much less regular. Also there is a marked tendency to show two or more periods of sleep instead of one for each circadian day.
In some ways this pattern of sleep is in between that of Non-24 Hour Sleep Wake Cycle Disorder and that of Sleep Wake Cycle Disorder – Irregular Type. In the irregular type of sleep disorder, the person sleeps at almost random times of day or night and for varying lengths of time. Usually there are several short periods of sleep scattered at various time around the clock.
My sleep has not become completely irregular, but it is getting there. This is, to put it mildly, not a good thing. N24, bad as it is, has a least a little predictability to it. I could never predict my sleep out several weeks as some very regular N24s could do. But I could at least predict it fairly well 5 or 6 days out. Now I can barely predict what it will do from one day to the next and the urge to sleep or be awake comes upon me at almost random times.
Usually irregular sleep patterns are associated with conditions involving brain damage (injuries, tumors) or deterioration (dementia). However I suspect that in cases of severe circadian disorder the circadian system may deteriorate over time, leading to an evolution towards an irregular sleep pattern. My co-blogger has remarked that her DSPS sleep has some irregular elements as well.
Instead of a static snapshot of sleep which classifies the disorders as DSPS, N24 or irregular, research needs to look at sleep disorders as dynamic, evolving conditions. If someone has say, heart disease, we understand it will manifest itself differently at age 20 and 40 and 60. The same may be the case with circadian disorders. I had some sleep abnormalities from birth, classic DSPS from age 15 to 27, and N24 from then on. Now I seem to be trending towards irregular sleep. My approach to coping with this condition will have to change as well, but how that will happen I don’t yet know.
–posted by LivingWithN24 (James Fadden)
Next post: 61. Questions and answers about Non-24