xxxi. Light Therapy Recommendations, 1999

23 February 2007 at 11:47 | Posted in Circadian rhythm | Leave a comment
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Continued from the previous entry. From a 1999 article.

 RECOMMENDATIONS FOR SPECIFIC DISORDERS:

1. Delayed Sleep-Phase Syndrome (DSPS) 

2.  Advanced Sleep-Phase Syndrome (ASPS)

3. Non-24-Hour Sleep-Wake Syndrome (NON-24)

 

1. DSPS

Delayed sleep-phase syndrome is a disorder in which the major sleep episode is delayed in relation to the desired clock time. It results in symptoms of sleep-onset insomnia and/or difficulty in awakening at the desired time. Core body temperature minimum and peak of the melatonin rhythm are shifted to later in the morning than normal.

Treatment Objectives and Indications 

Based on the human PRC, a phase-advance will take place if the subject is exposed to light after the peak of melatonin rhythm or the minimum of core body temperature, usually in the early morning.

a) Light therapy appears to have potential utility in the treatment of DSPS.

For use of light therapy in the treatment of DSPS, 2000 to 2500 lux from 6 to 9 a.m. and optionally wearing dark goggles from 4 p.m. to dusk is an approach that has been studied with apparent effectiveness. However, some patients will have a temperature minimum during or after this light exposure time period and may not respond or respond paradoxically with a phase-delay rather than a phase-advance. In those patients who do not respond as expected and in whom information such as sleep diary entries or, if available, melatonin rhythm or core body temperature suggests a peak rhythm or core body temperature minimum at a time after the exposure to light therapy, a later morning time period for light therapy (e.g., after 9 a.m.) may be tried.

b) The minimum or optimal duration of light therapy for DSPS is unknown.  

In one study, 12 days of bright light was successful in shifting core body temperature and improving sleep efficiency and was rated better than dim light. In addition, the duration of therapy necessary to provide continuing effectiveness is unknown as is the possibility of tolerance (i.e., loss of benefit over time) to the therapy.

2. ASPS

Advanced sleep-phase syndrome is a disorder in which the major sleep episode is advanced in relation to the desired clock time.  It results in symptoms of compelling evening sleepiness, an early sleep onset, and an awakening that is earlier than desired. Core body temperature minimum and peak melatonin rhythm occur earlier in the morning than usual.

Treatment Objectives and Indications

Based on the human PRC, a phase-delay will take place if the subject is exposed to light soon after the dim light melatonin secretion onset or core body temperature maximum, usually in the evening.

a) Light therapy appears to have potential utility in the treatment of ASPS.

For the use of light therapy in the treatment of ASPS, 2500 lux for four hours from 8 p.m. to midnight, or 4000 lux for two or three hours from 8 or 9 p.m. to 11 p.m. are approaches that have been studied with apparent effectiveness.  However, some patients may have a temperature maximum substantially before this time period and may not respond with a phase-delay.  In those patients exposure to light at an earlier time period may be attempted.

b) The minimum or optimal duration of light therapy for ASPS is unknown.

In one study 25 days of bright light was successful in shifting core body temperature and improving sleep efficiency and performance.  In addition, the duration of therapy necessary to provide continuing benefit is unknown as is the possibility of tolerance (i.e., loss of effectiveness over time) to the therapy.

3. NON-24 

Non-24-hour sleep-wake syndrome is a syndrome in which patients fall asleep at a different time each day because the circadian period differs from 24 hours.  For example, on day one the patient may fall asleep at 10 p.m., day two at 12 midnight, day three at 2 a.m. etc. Patients may have either insomnia or hypersomnia depending on which phase of the circadian cycle they are in when trying to sleep. Core body temperature cycles may be greater in length than normal. Blind individuals are a special case since the normal sleep-wake cycle may be longer than 24 hours and if no light reaches the SCN, there may not be natural resetting of the circadian clock to 24 hours. Totally blind individuals, such as those whose eyes have been enucleated, comprise a minority of the legally blind. These individuals will have no retinal response to light and may have free-running circadian rhythms. Light therapy is of no confirmed benefit in these patients. However, some blind individuals who have this syndrome may be responsive to light therapy despite no apparent perception of visible light.

Treatment Objectives and Indications

Currently there are very few studies on which to base a strategy but some reports suggest that morning light may work. Other studies are negative. Based on the phases of the light PRC, a phase-advance will take place if the subject is exposed to light at a time soon after the peak melatonin rhythm or the core body temperature minimum in the morning, which would regularize the circadian cycle to a more typical sleep/wake cycle. However, care needs to be taken to ensure that the patient is not in a portion of the PRC such that the morning light exposure occurs after the dim light melatonin secretion onset or the core body temperature maximum and before the temperature minimum or peak melatonin rhythm. In such a case, there could be no response or a phase-delay.

a) Light therapy may be of benefit in treating some blind patients with non-24-hour sleep-wake syndrome.

For the use of light therapy in the treatment of non-24-hour sleep-wake syndrome, 3300 lux for one hour between 6 and 8 a.m. is an approach that has been studied with apparent effectiveness for blind persons. No recommendation for sighted individuals is made since insufficient data is available. If the expected response does not occur, an adjustment of the timing of the light exposure may be attempted to produce the phase-advance or phase-delay, depending on information such as sleep diary entries or, if available, core body temperature maximum or minimum or dim light melatonin secretion onset or the peak of the melatonin rhythm.

b) The minimum duration of light therapy for non-24 hour sleep-wake syndrome is unknown.

In one study 14 days of bright light was successful in improving symptoms and increasing melatonin secretion. In addition, the duration of therapy necessary to provide continuing effectiveness is unknown as is the possibility of tolerance (i.e., loss of effectiveness over time) to the therapy.

 FOR SYNDROMES ASSOCIATED WITH PHASE ADVANCES AND DELAYS, LIGHT THERAPY APPEARS TO HAVE CLINICAL UTILITY.

 

 My doctors didn’t know that in 1999.

Did yours?

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Next:  xxxii. Chronotherapies for DSPS

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xii. Circadian rhythm disorders

27 November 2005 at 11:14 | Posted in Circadian rhythm | 6 Comments
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There are a great many sleep disorders. I read recently that an official list of them had been pared down to about 70. Many have to do with not getting enough sleep, or getting sleep of poor quality by several criteria. Some have obvious causes, such as chronic pain, frequent stops in breathing etc.

My interest is in the timing of sleep as my sleep seems otherwise normal. As the experts put it, I have normal “sleep architecture”. (For a good, short explanation of sleep architecture — stages and brain waves — see this page from Feinberg School of Medicine at Northwestern University in the USA.)

Nearly all of us can reset our clocks daily, adjusting the various rhythms to 24 hours. As much as I’ve read about it, I’ve not found a good enough explanation for being able to adjust to 24 hours while not being able to adjust to sleeping midnight to eight or so.

I’m not immune to the light/dark cycle. I need to get up at noon. I fly 8 hours east or west, go through jet lag like anyone else and within days I need to get up at noon in the new location. This is built in. I’m not the only one. I’d just like to understand it better.

A Japanese paper (2004) suggests these possible mechanisms:

  • reduced sensitivity of the oscillator to photic entrainment,
  • an intrinsic period beyond the range of entrainment to the 24 hour day, and
  • abnormal coupling of the sleep/wake cycle to the circadian rhythm.

 

The least common and most debilitating circadian disorder is the one where body temperature, melatonin secretion, sleep and other rhythms vary several times a day, in and out of phase with one another, so called Irregular Sleep/Wake Disorder. This has been reported in humans who’ve been in accidents and had physical injuries to the hypothalamus. It’s also been provoked by surgery in lab animals.

One of the most rare disorders which occurs naturally is called Non-24. Sufferers simply(?) live on a 23, 25 or 26 hour cycle, getting up one hour later each day for example, thus coming in sync with the earth’s rotation every few weeks. Their rhythms are in sync internally, just not with the light/dark cycle outside. Most, but not all, of these people are blind. 

ASPS, Advanced Sleep-Phase Syndrome, is also rare. These people fall asleep and awaken much earlier than normal. The disorder runs in families, and an American family has been studied intensively the last few years. Research on their genetic mutation was published in 2001. “Detailed sequence studies of the candidate human gene, hPer2, in the affected family members, revealed a key change in a single amino acid — from serine to glycine — at position 662 in the hPer2 protein.” The alteration “occurred in the portion of the hPer2 protein that governed binding to an enzyme called casein kinase one-epsilon (CK1e ).” In animal models, this enzyme regulates “proteins involved in controlling the length of circadian rhythms.”

Now this is beyond me, but it would appear that these disorders may be genetically programmed. Though ASPS is rare, it seems reasonable that researchers start there, since one can compare the DNA of people who are related to one other.

DSPS, Delayed Sleep-Phase Syndrome, is a bit more common. Studies indicate that somewhat more than one in a thousand adults have DSPS (Japan 0.13%, Norway 0.17%). It runs less commonly in families, but it doesn’t seem unreasonable to guess that its cause may be similar to that of ASPS.
 
Clearly, anyone whose health cannot tolerate frequent forced awakening earlier than 10 a.m., will have few real choices in our society. Thus, hardcore (inflexible) DSPS must be considered a disability.

Another disorder which may be related to the others is Seasonal Affective Disorder, SAD. Sufferers are normal in summer, have problems of mood, weight gain etc. when days get shorter and can often be treated successfully by bright light therapy. It seems likely that they may have a mild form of ASPS or DSPS which is “treated” by morning/evening daylight when days are long.

Diurnal preference, spoken of as “morningness”, larks, and “eveningness”, owls, is also a subject of study, the field of chronobiology. This is, reasonably enough, connected to one’s circadian rhythms. However, it does not appear that ASPS is an extreme morningness chronotype nor DSPS an extreme eveningness chronotype. The internal relationships among the various rhythms do not place these conditions on a simple continuum.

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Next post:  xiii. DSPS-sleep

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vi. The timing of sleep

22 November 2005 at 23:45 | Posted in Circadian rhythm | Leave a comment
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We have several circadian rhythms which are determined by our body clocks.  The most obvious of these is the sleep/wake cycle.  We can and do override nature’s signals – otherwise alarm clocks wouldn’t have been invented.  
 
We vary widely in our ability to live on a schedule different from the built-in one.  Some people seem to have little trouble adjusting to shift work; others prefer to avoid it at all costs.  Some people struggle with jet lag and even with the switch to or from Daylight Savings Time; others ask “What’s the big deal?”   
  
Have scientists done any research into these differences among us?  They’ve done a great deal of work explaining what adjustments the body has to accomplish in such situations, but I can’t find anything about why one person adjusts quickly and easily while another (of the same age) just simply can’t. 
 
In the presentation below I’m talking about adults who do adjust their body clocks to a 24-hour day and who have adequate sleep quality.  With thanks to Darren for helping me to reason along these lines, I think adults are of four types with regard to the timing of sleep:

1) Normally timed body clock, flexible.  Preferred wake-up time is about 7 a.m. and there’s no problem getting to sleep eight or so hours earlier.  While an afternoon or night shift might wreak havoc with social life, it is no big deal physically / mentally.

2) Normally timed body clock, inflexible.  Bedtime and wake-up as above but with as little variation as possible.  Attempts to work or live on another schedule have caused such physical and/or mental discomfort / illness that any pressure to try it again will be resisted.

3) Abnormally timed body clock, flexible.  Seven a.m. is an unfortunate time to have to get up, but with sufficient self-discipline the night before, it can be done.  No big deal, but some sort of freelance career, or an afternoon or night shift, might be preferable.

4) Abnormally timed body clock, inflexible.  Those who’ve been paying attention during this lesson now see where this is going.  A person whose biological rhythms say that waking up at around noon (or at around 3 a.m.) is the only way to stay healthy, is theoretically no worse off than number 2 above.  Just do it!  Just stick to the necessary bedtime of 4 a.m. (or 7 p.m.), sleep your eight hours and you’re fine.

These ‘Type 4’ individuals have ASPS or DSPS – I’ll get back to what the alphabet soup stands for.

When one of them works a day shift, the boss and the doctor are going to say, as mine have done:  “I believe that you are not willfully telling lies; I know you too well for that.  At the same time I cannot see how what you are telling me could be the case.  I know of no explanation, and I can’t imagine how you really feel.”

Well, of course, those are the generous comments.  I’ll leave the less generous ones to your imagination.

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Next post:  vii. Sleep and OTHER daily cycles

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