Tags: Actigraph, Circadian rhythm, Light therapy, Phase response curve, Suprachiasmatic nuclei, Suprachiasmatic nucleus
Practice Parameters for the Use of Light Therapy in the Treatment of Sleep Disorders appeared in SLEEP, Vol. 22, No. 5, 1999. The authors, Chesson et al, were all connected to universities and medical institutions in the USA.
The clinical guidelines developed by the Standards of Practice Committee were reviewed and approved by the Board of Directors of the American Academy of Sleep Medicine. The guidelines provide recommendations for the practice of sleep medicine in North America regarding the use of light therapy for treatment of various sleep disorders.
“These practice parameters define principles of practice that should meet the needs of most patients in most situations.”
As the PDF apparently no longer is available on the Internet and the document is found only in Google’s html version, I’m offering some excerpts here. I’m leaving out altogether the sections on shift work and other voluntary shifts of sleep-wake schedules, sleep disturbances in the elderly, jet lag and Seasonal Affective Disorder (SAD). Update, December 2010: the PDF is now here, hat tip to ttt.
Almost 10 years old, the guidelines can hardly be said to be up-to-date. Much of the information is, however, correct, and it is interesting to see what doctors “should have known” at the turn of the century, at least in the USA. [Emphasis, bold, is mine.]
From the INTRODUCTION: Endogenous circadian rhythms are in large part regulated by the hypothalamic suprachiasmatic nuclei (SCN). The SCN are key regulators of sleep, as they regulate rhythms that promote sleep and wakening. It is now recognized that a number of sleep disorders are linked to abnormal circadian rhythms or to a lack of coordination of the sleep-wake cycle with the individual’s circadian rhythms. One of the most potent external factors that can alter the period of the SCN is light exposure.
From BACKGROUND: Over the past two decades, laboratory studies have demonstrated that scheduled light exposure can produce a dose-dependent phase shift in the endogenous circadian rhythms of a variety of variables. These variables include plasma or saliva melatonin, core body temperature, cortisol and a propensity to sleep.
The rationale for the use of light therapy evolves from the observation that circadian rhythms in humans can be phase-shifted by scheduled exposure to light. Because of an endogenous pattern of light sensitivity, the direction of the phase shift varies with the timing of the light exposure. The responses of circadian rhythms to light exposure have been summarized in Phase Response Curves (PRC). The PRC appears phase-locked to the core body temperature and plasma melatonin concentration rhythm. In healthy young subjects, with a normal sleep pattern and temperature curve, the core body temperature minimum typically occurs about two hours before habitual wake time (around 4 to 5 a.m.).
Light exposure prior to the endogenous minimum of the core body temperature will shift rhythms to a later clock time (i.e., will delay rhythms).
Light exposure just after the endogenous circadian body temperature minimum will shift rhythms to an earlier clock time (i.e., will advance rhythms).
From SAFETY and SIDE EFFECTS:
Light therapy appears to be a generally safe treatment option for some circadian rhythm disorders…
Rarely, light therapy may provoke a hypomanic state in patients with bipolar affective disorders.
TREATMENT OBJECTIVES, INDICATIONS and FOLLOW-UP: Treatment is indicated only if there is a desire on the patient’s part to resolve symptoms. The objective is to achieve a sleep onset at either a more socially acceptable time or at a time that provides sufficient sleep in keeping with the work schedule or lifestyle.
Objective documentation is generally limited to a shift in the core body temperature minimum, a shift in the onset of dim light melatonin secretion or in the peak of the melatonin rhythm, information the patient has recorded in diaries, or actigraphic measurement of rest/activity patterns.
¤ ¤ ¤ ¤ ¤ ¤ ¤
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)