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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