Circadian rhythms, light and sleep
Scripps Clinic and Research Foundation
Modern evidence suggests that the best treatment for insomnia related to body clock disturbances involve regular specifically timed exposure to bright light.
Effects of phototherapy in patients with delayed sleep phase syndrome
Psychiatry Clin Neurosci 1999 Apr;53(2):231-3
Phototherapy was given to six patients with delayed sleep phase syndrome (DSPS). Phototherapy was administered to each patient for 5 days, and this treatment not only advanced the delayed sleep phase but also delayed the time of minimum body temperature in all patients. Decreases in total sleep time and amounts of stages 2 and REM were observed after phototherapy. These results suggest that phototherapy is effective even in the short term in advancing delays in sleep phase and time of minimum body temperature in DSPS patients.
A multicentre study of sleep-wake rhythm disorders: therapeutic effects of vitamin B12, bright light therapy, chronotherapy and hypnotics
Psychiatry Clin Neurosci. 1996 Aug;50(4):203-209
106 subjects with primary sleep-wake rhythm disorders [13 non-24 hour sleep/wake syndrome (non-24), 76 delayed sleep phase syndrome (DSPS), 11 irregular sleep-wake pattern (irregular) and 6 long sleepers] were treated with vitamin B12, bright light, chronotherapy and/or hypnotics. These therapies caused moderate or remarkable improvement in 32% of the non-24, 42% of DSPS, 45% of irregular and 67% of long sleepers. A lack of adequate sleep, unpleasant feelings at waking and daytime drowsiness were also improved in DSPS.
Light treatment for sleep disorders, Consensus Report IV: Sleep phase and duration disturbances
J Biol Rhythms. 1995 June;10(2):135-147
Advanced and delayed sleep phase disorders, and the hypersomnia that can accompany winter depression, have been treated successfully by appropriately timed artificial bright light exposure.
Light treatment shifts (-) rhythms in NASA shiftworkers
Chronobiology International. 1995 April;12(2):141-151
During four different Space Shuttle missions in the past two years light treatment was used to help workers adjust to their shiftwork schedules. (The shiftworkers) reported that this improved daytime sleep, and night-time alertness on duty and reduced fatigue, and physical and emotional symptoms, compared to an untreated control group. The treated subjects had peak melatonin during the daytime (rest) period, the control group had peak melatonin during the night shift.
NASA, the US space agency, were the very first people to make practical use of lights to alter circadian rhythms; it remains in use today, not only for astronauts but also for the ground crew. The Light Visor is currently in use by astronauts in the International Space Station.
Exposure to bright light and darkness to treat physiologic maladaptation to nightwork
N Engl J Med. 1990 May 3;322:1253-1259
Working at night results in a misalignment between the sleep-wake cycle and the output of the hypothalamic pacemaker that regulates the circadian rhythms of certain physiologic and behavioural variables. We evaluated whether such physiologic maladaptation to night-time work could be prevented effectively by a treatment regime of exposure to bright light during the night and darkness during the day. We assessed the function of the circadian pacemaker in five control and five treatment studies to assess the extent of adaptation in eight normal young men to a week of night work.... We conclude that maladaptation of the human circadian system to night work, with its associated decline in alertness, performance and quality of daytime sleep, can be treated effectively with scheduled exposure to bright light at night and darkness during the day.