Sleep and Circadian Rhythm Disorder
Getting enough sleep daily is important. Without it, we’re tired and lethargic, we have problems concentrating, and have difficulty handling even routine tasks. We may be grumpy and irritable. And that’s after just one night of bad sleep. Imagine the cumulative effect of bad sleep over a course of weeks, months, or years. A natural insomnia treatment for sleep disorders becomes even more important.
One in four people worldwide experience difficulty sleeping at some point, and one in ten of these people claim to have slept poorly most or every night for a month or more. These sleep difficulties could result from any of sixty distinct medical causes, varying from psychological causes (for example, depression or anxiety) to physical illness (e.g., restless legs syndrome, periodic leg movements), to conditions that produce pain.1
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For one in four people with sleep difficulties, the cause is a desynchronization between sleep timing and other daily (“circadian”) body rhythms. A treatment for circadian rhythm sleep disorder is that same as for insomnia treatment.2
Bright light treatment (which consists of daily administration of artificial bright light of appropriate intensity, duration, and time of use) has been shown to be very useful in treating a number of these sleep disorders & circadian rhythm disorders, specifically: Delayed Sleep Phase Syndrome (DSPS), Advanced Sleep Phase Syndrome (ASPS), jet lag, problems associated with shift work, non-24-hour sleep-wake syndrome, dyschronosis, and age-related sleep maintenance insomnia.3
Each of these problems will be described in further detail below, and their treatment with bright light [also see Bright Light Treatment section] will also be discussed. In the words of one clinical study, “Exposure to light is the primary synchronizer of the human circadian pacemaker.”4 With all these sleep disorders, treatment may need to occur during times when bright sunlight is unavailable, so a bright light box purchase should be considered.
“Patients are unable to build or buy other lighting that is as satisfactory as the boxes specifically manufactured to provide bright light.”5
Delayed Sleep Phase Syndrome (DSPS)
Perhaps the most common of the circadian rhythm sleep disorders is Delayed Sleep Phase Syndrome (DSPS), which occurs mainly in teenagers and young adults. It occurs when a person’s body clock is running later than it should, resulting in sleep-onset and wakening times that are very late in relation to the daily cycle of life. It is at the extreme end of the ‘night owl’ syndrome: a night owl will typically choose to stay up until midnight, and sleep until 8 in the morning; a person with DSPS is unable to initiate sleep until well after 1 or 2 am, and has extreme difficulty awakening until late morning or close to noon.6, 7
During adolescence, the biological clock normally shifts to a later schedule. Most teenagers prefer to have an active evening social life, staying up until 1 or 2 am, and are sleepy through morning classes. For teenagers with DSPS, the problem is much worse: they stay up until after 4 am, and often either arrive very late for school or don’t even show up at all (when they do, they may fall asleep in class).8 As a consequence, their grades suffer, family tensions rise, and life becomes chaotic for both the teen and those close to him.
Exposure to bright light (10,000 lux for at least 30 minutes daily or 2,500 lux for at least 2 hours) as soon as possible after awakening, has been found to be extremely helpful in resetting the body clock to an earlier time.9 After some time, which may be days or weeks, depending on individual response, those employing this method will begin finding it easier to get up earlier and fall asleep earlier. As this happens, treatment time should be advanced as well.10, 11
Once the preferred schedule is achieved, the user may cut back to shorter daily light sessions at the same time each day to maintain this schedule. Unfortunately, DSPS patients who discontinue use of the bright light tend to relapse after several days, so maintenance light treatment is necessary to continue the new sleep pattern.12, 13
Advanced Sleep Phase Syndrome (ASPS)
At the opposite end of the spectrum are those affected by Advanced Sleep Phase Syndrome (ASPS), a condition that primarily affects older people.14It is characterized by early sleep onset and early morning awakening, with the inability to maintain sleep past the predawn hours (e.g., 3-4 am).15 As with Delayed Sleep Phase Syndrome [see above section], people with ASPS typically sleep the same number of hours as those without sleep phase disorders, they just experience it out of sync with the world’s daily living patterns.
Again, bright light treatment is highly effective in treating this problem. Used in the evening – about 2 to 4 hours before scheduled bedtime – 10,000 lux of light for at least 30 minutes or 2,500 lux for at least 2 hours daily will gradually delay sleep onset, with a subsequent delay of awakening time. If the bright light treatment is found to be too energizing at bedtime, it should be scheduled to end at least 1 to 2 hours before the scheduled bedtime. Once the target schedule is achieved, it can be maintained by regular use of a shorter duration of bright light in the evening.
Jet Lag
These days, air travel is so convenient and affordable that almost everyone is familiar with the symptoms of jet lag: sleeplessness at night, and extreme fatigue during the daytime. These effects occur as a result of crossing multiple time zones and having one’s sleep/wake schedule out of sync with the local time, and is not to be confused with the weariness of long hours of travel which result from lack of sleep (the latter can be alleviated simply by catching up on lost sleep).17
Most people crossing more than one time zone in a westward direction (for example, from New York to Los Angeles), will experience symptoms similar to those of Advanced Sleep Phase Syndrome [see related section above]. Eastbound travelers (from the US to Europe, for example) will experience symptoms similar to those of Delayed Sleep Phase Syndrome [see related section above].18
Symptoms of jet lag can be alleviated, and quick adaptation to the new time zone can be achieved by using or avoiding bright light at various times of day, as outlined below.19
- When attempting to advance the body clock (to an earlier time, as in eastbound travel) up to 6 time zones, bright light applied in the morning on the day of departure and perhaps for one or two days beforehand can significantly reduce the time necessary to adjust to the new time zone.
- If your travel brings you more than six time zones eastward, it might be easier to delay your sleep and skip a day (stay awake for 36 hours, for example, then go to sleep at the appropriate time in the new time zone.
- Westbound travel is a lot easier for most people, as it’s generally pretty easy to stay awake for a few extra hours than it is to go to sleep early (when you’re not tired), since most people have roughly a natural 25-hour daily rhythm. If you anticipate difficulty staying awake for the extra hours, expose yourself to bright light in the evenings upon arrival and perhaps for a few days before your trip. Avoid bright light in the morning at your destination until early morning awakening disappears.
Shift Maladaptation Syndrome
One in five workers in industrialized nations are shift workers.20 In the United States, at least 21 million people work shifts other than the typical 9-to-5 day shift. Forty to eighty percent of industrial night shift workers report disturbed sleep, the cardinal symptom of what has been described as ‘shift maladaptation syndrome.’21 Other characteristic symptoms are fatigue or lack of alertness during waking hours, gastrointestinal problems, impaired performance, high accident or near-miss rates, depression and personality changes, and difficult interpersonal relationships.22, 23
Averaging one to 1.5 hours less sleep per 24 hour period than day workers, both permanent night workers and rotating shift workers on the night shift experience sleep deprivation caused by a misalignment of the sleep-wake cycle to biological circadian (daily) rhythms.24 Sleep deprivation and this misalignment of rhythms are two of the most important factors in decreased performance and increased accident rates associated with night work, and may also impact other health consequences of shift work (e.g., digestive and cardiovascular). Therefore, changing circadian rhythms to match the imposed sleep-wake schedule may positively impact the overall health of night workers.25
Besides the permanent night shift, another common shift schedule in use today is a rotating shift, where employees work all three shifts (day-evening-night, or morning-afternoon-night) in rotation. While the exact schedule and hours vary from company to company, an example of a rotating shift schedule (8 days long) follows: Evening-Day-Day-Evening-Night-Night, followed by two days off, then repeat the schedule.
Because of both social and physiologic pressure to conform to a normal sleep-wake pattern, night shift workers typically revert to sleeping at night on their days off, which quickly reverse any partial adaptation to the night shift they may have attained.26 Abruptly attempting to sleep at normal hours after several nights of working and sleeping during the day is biologically equivalent to a 6- to 10-hour eastbound jet flight, resulting in disrupted sleep, just as in jet lag [see above section].27
Studies conducted both in the laboratory (in temporal-isolation chambers or in laboratories where subjects were confined to the lab) and in the field (where subjects lived at home and went to work as usual) have shown the importance of properly timed exposure to bright light and darkness in resetting the circadian pacemaker – the internal clock which controls our circadian rhythms.28
In fact, bright light exposure is so powerful a cue for the circadian pacemaker that it alone can reset the body clock by as much as 12 hours within only a few days.29 The timing, intensity, and duration of the light exposure is critical for phase shifting the body clock; given at the wrong time of day or night, bright light of sufficient intensity and duration may have no effect on the body clock.30 However, properly timed, it is so successful that NASA, after initiating a bright light program for both Space Shuttle astronauts and the payload ground crew who must work nights during missions, has made the program a permanent part of their Space Shuttle program.31
To properly determine the timing of bright light application requires testing in a sleep laboratory by trained sleep specialists, to test such things as core body temperature and melatonin secretion rhythms. This approach, which is time intensive, may not be practical for most shift workers to undergo.
Two approaches have been suggested which would allow people to try bright light treatment to shift their own rhythms without knowing exactly what their current rhythms are. In the first method, which has been called a ‘buckshot’ approach, it is suggested that long durations (many hours at one time) of light be administered close to the timing of the daily temperature minimum, which typically occurs around the midpoint of sleep, in the hope of hitting the right time to reset the body clock. This approach could, theoretically, result in great gains in changing circadian rhythms – as much as a 4-5 hour shift in one night; however, the direction of that gain may not be the one desired.32
An alternative approach to use, when the direction (either advancing or delaying rhythms) is important, requires bright light exposure aimed to one side or the other of the expected temperature minimum, and gradually moved closer on successive days so that it eventually would come close enough to produce the desired direction of phase shift. If the goal is to advance circadian rhythms to an earlier time, one would try light shortly after awakening, and gradually move it earlier each day until the correct timing is found. If the goal is to delay rhythms, however, one would use the light before going to sleep, and gradually move it later each day.33
Another tool for shift workers who wish to improve their sleep is daytime oral melatonin administration, which lowers core body temperature during the day and prevents the temperature spike which signals the body and brain that it’s time to wake up. This in turn allows for better daytime sleep.34However, researchers caution that more studies must be conducted to determine optimal timing and dosage of oral melatonin, as well as give sufficient evidence for its effectiveness.35
Comparisons of bright light and melatonin administration for shift workers show increases in the duration and reported quality of sleep for both treatments, with bright light having a slight edge over melatonin. Only bright light, however, is associated with consistently improved performance levels throughout the night shift, improved sleep quality as measured by laboratory tests, and greater shifts in circadian rhythms.36 Though melatonin may be helpful in improving sleep for shift workers, at present, research does not support its use as a primary course of treatment.
While shifting circadian rhythms (and maintaining those shifts) might be the best approach for permanent night shift workers, a different approach might be best for rotating shift workers, especially those on rapidly rotating schedules. Rapidly rotating shift workers might benefit from a plan that temporarily ‘disconnects’ their body clock that regulates sleep and core body temperature. As previously discussed, melatonin ‘masks’ the rise in core body temperature that signals the end of sleep, allowing sleep to be maintained longer than normal.37
Non-24 Hour Sleep-Wake Syndrome and Dyschronosis
Almost everyone has a built-in daily (circadian) rhythm of more than 24 hours, usually between 24.5 and 25.5 hours.38 Most people are naturally able to ‘resynchronize’ their body clock each day to the 24-hour light-dark cycle we call a day, but for a small portion of the population, this resetting of the body clock does not occur, and non-24-hour sleep-wake syndrome results.
The sleep-wake cycle gradually moves later and later each day, while the person continues to function in society on a 24-hour schedule. Though the sleep-wake cycle initially matches the daily rhythm of life, after a short time, it moves out of sync, and the person has difficulty falling asleep until well into the night. Gradually, the person is unable to sleep at all at night, and experiences extreme sleepiness during the daytime hours. Shortly after that, the person is able to sleep in the early part of the night, but awakes early in the morning. Eventually, the sleep-wake cycle again moves back into alignment with the person’s daily rhythm and the person sleeps well for a short time, until the cycle begins again.39
The majority of reported case of non-24-hour sleep-wake syndrome occur in blind patients with no conscious perception of light.40 Bright light is the most powerful synchronizer of human circadian rhythms, and researchers have determined that in some blind people, the pathway that transmits light signals to the brain remain intact (allowing the daily resetting of the body clock to occur) despite a complete lack of conscious perception of light and lack of pupillary response to the bright light of an indirect ophthalmoscope.41
Treatment has proven extremely difficult for this problem. Medication is of very limited, if any, help.42 There is evidence, however, that bright light treatment administered early in the subjective morning (that is, shortly after awakening) can have a positive effect on the condition.43 Another helpful approach is to adhere to a strict 24-hour schedule with social time cues (meals, interpersonal interaction, etc.) at specific times each day to facilitate the resynchronization of the circadian rhythm.44
A related problem, dyschronosis, mainly occurs in children with severe brain injury. These children have a sleep disorder that is debilitating for them and for their families: they sleep in short ‘snatches’ throughout the day and night, with a complete lack of sleep consolidation. In one study, nighttime sleep – the longest period of daily sleep – averaged only 2.5 hours, with total sleep time for the day of 5 hours, in 15 to 80 minute segments scattered around the clock. Medication management was ineffective; however, five of the fourteen subjects (36%) responded well to bright light treatment administered daily for 45 minutes each morning. In fact, after 6 months of treatment, these responders were sleeping through the night with only one or two short daytime naps.45
Age-Releated Sleep Maintenance Insomnia
Complaints of sleeping difficulties increase with age. More than half of all senior citizens (age 65+) report regular problems with sleep.46 Although the elderly account for 40% of hypnotic medication (sleeping pill) prescriptions, these medications are of little benefit in this age group.47 In 1990, a National Institutes of Health Consensus Development Conference recommended research into more effective treatments, with an emphasis on non-pharmacological methods.48 Older people often complain about getting less sleep, of waking frequently at night, of waking up too early in the morning, and of being sleepy during the day and consequently napping.49
Sleep disturbances may be caused by an underlying medical (e.g., sleep apnea, arthritis) or psychiatric (e.g., depression) illness. Treating the primary illness often leads to resolution of the sleep complaints.50 For many, though, there is no underlying medical problem causing the sleep disturbance: the problem is a misalignment of the sleep-wake cycle to other daily cycles of body temperature, melatonin production, etc., resulting from a lack of daily exposure to intensities of light sufficient to anchor daily rhythms. Light exposure among seniors, especially those living in nursing homes, is much lower than that for younger adults – in one study, half the subjects spent no time at all in light greater than 1,000 lux.51
As we age, our circadian clock seems to advance, causing Advanced Sleep Phase Syndrome [see Advanced Sleep Phase Syndrome (ASPS) section]. One study reports that older subjects have a shorter daily temperature rhythm than young subjects – only about 22.5 hours, as opposed to 24.5 to 25.5 hours.52 In other words, older adults may have shortened daily rhythms, which lead necessarily to a significant daily advance in sleep and other rhythms.
Bright light exposure in the early evening or late afternoon often helps lengthen the circadian rhythms of elderly people with sleep maintenance insomnia, and improves both the quality and duration of their sleep.53 The application of bright light is the same as for Advanced Sleep Phase syndrome [see above section].54 When light treatment is withdrawn, improvement is maintained for a short time. However, after 1-3 months following withdrawal, some subjects again experience early morning awakening, and require bright light treatment to readjust and to maintain their circadian rhythms.55
1 Smolensky, M & L Lamberg: The Body Clock Guide to Better Health: How to Use Your Body’s Natural Clock to Fight Illness and Achieve Maximum Health. New York:Henry Holt & Co., 2000, p 339.
2 ibid.
3 Terman, M, AJ Lewy, D-J Dijk et al.: Light treatment for sleep disorders: Consensus report. IV. Sleep phase and duration disturbances. J Biol Rhythms, 10(2): p 136, 1995.
4 Duffy, JF, RE Kronauer & CA Czeisler: Phase-shifting human circadian rhythms: Influence of sleep timing, social contact and light exposure. J Physiol, 495(1): p 295, 1996.
5 Kripke, DF & RT Loving: Bringing therapy to light. Sleep Rev, Winter 2001.
6 Terman, p 136.
7 Smolensky, p 342.
8 ibid.
9 Kripke.
10 ibid.
11 Terman, p 138.
12 Kripke.
13 Terman, p 138.
14 ibid, p 136.
15 ibid.
16 ibid, p 138.
17 Oren, DA, W Reich, NE Rosenthal et al.: How To Beat Jet Lag: A Practical Guide for Air Travelers. New York: Henry Holt & Co., 1993, pp 2-3.
18 Kripke.
19 ibid.
20 Eastman, CI: Light treatment for circadian and sleep disturbances of shift work. Light Treatment and Biological Rhythms, 6: p 55, 1994.
21 Wagner, DR: Disorders of the circadian sleep-wake cycle. Neurologic Clinics. 14(3): p 664, 1996.
22 ibid.
23 Eastman, 1994, p 55.
24 Wagner, p 665.
25 Czeisler, CA, MP Johnson, JF Duffy et al.: Exposure to bright light and darkness to treat physiologic maladaptation to night work. N E J Med, 322(18): p 1258, 1990.
26 Eastman, CI, Z Boulos, M Terman et al.: Light treatment for sleep disorders: Consensus report. VI. Shift work. J Biol Rhythms, 10(2): pp 158-159, 1995(a).
27 Wagner, p 665.
28 Eastman, 1995(a)
29 Czeisler, 1990, p 1254.
30 ibid, p 1258.
31 Eastman, 1994, p 59.
32 Eastman, CI, L Liu & LF Fogg: Circadian rhythm adaptation to simulated night shift work: effect of nocturnal bright-light duration. Sleep, 18(6): p 405, 1995(b).
33 ibid.
34 Dawson, D, N Encel & K Lushington: Improving adaptation to simulated night shift: timed exposure to bright light versus daytime melatonin administration. Sleep, 18(2): pp 12 & 18, 1995.
35 Wagner, p 666.
36 Dawson, p 19.
37 ibid, p 20.
38 Wagner, p 651.
39 ibid, p 658.
40 ibid.
41 Czeisler, CA, TL Shanahan, EB Klerman et al.: Suppression of melatonin secretion in some blind patients by exposure to bright light. N E J Med, 332: p 8, 1995.
42 Wagner, p. 659.
43 Czeisler, 1995, p 10.
44 Wagner, p 659.
45 Guilleminault, C, CC McCann, M Quera-Salva et al.: Light therapy as treatment of dyschronosis in brain impaired children. Eur J Phediatr, 152: pp 754-759, 1993.
46 Ancoli-Israel, S: Sleep problems in older adults: Putting myths to bed. Geriatrics, 52(1): p 20, 1997.
47 Campbell, SS, D Dawson & MW Anderson: Alleviation of sleep maintenance insomnia with timed exposure to bright light. J Am Ger Soc, 41(8): p 829, 1993.
48 ibid, p 834.
49 Ancoli-Israel, 1997, p 20.
50 ibid, p 25.
51 Ancoli-Israel, S, DW Jones, L Almendarez et al.: Light exposure in nursing home patients. Society for Light Treatment and Biological Rhythms Abstracts, 4: p 17, 1992.
52 Lack, L & H Wright: The effect of evening bright light in delaying the circadian rhythms and lengthening the sleep of early morning awakening insomniacs. Sleep, 16(5): p 440, 1993.
53 ibid, p 439.
54 ibid, p 436.
55 ibid, p 441.