ABSTRACT

Melatonin is an active sleep facilitating hormone and important cancer fighting antioxidant. Ordinarily it is produced by the pineal gland only when the eyes are in darkness. The use of artificial light at night decreases substantially the time people are in darkness and thus the time that melatonin is produced. This is considered by some to be one cause for the increasing incidence of breast and other cancers in industrialized countries. In addition, the availability of artificial lighting encourages poor sleep habits and/or sleep deprivation, which, in turn, can exacerbate various mood disorders. The fact that it is only the blue component of light that suppresses melatonin production provides a simple way to possibly reduce these and other health problems without radical changes of life style. This involves the use of devices, for example eyewear and specially coated lamps, that filter out light wavelengths below 530nm. The properties of such devices and some possible health effects resulting from their use are discussed.

Key words: melatonin, artificial light, sleep, mood disorders, cancer risk, bipolar disorder

1. INTRODUCTION

Melatonin, the strong antioxidant and sleep facilitating hormone, until quite recently, was believed to be produced by the pineal gland only when the eyes are in darkness [1]. In the same way, darkness is assumed to control the circadean clock, which in turn, through melatonin and other hormones, controls many of the body’s activities. Some researchers have come to believe that the use of artificial lighting at night in industrialized countries, since it reduces the time that melatonin is produced by the pineal gland, may disturb the natural behavior of many bodily functions.

It was recently shown conclusively, however, that it is only the blue component of light reaching the eyes that suppresses melatonin production [2,3]. With this in mind, as lighting developers, we have devised techniques of providing “blueless” light to the eyes in the evening before bedtime. This is accomplished by using light bulbs with coatings that do not transmit the blue light that suppresses melatonin, or by having subjects wear eyeglasses that filter out only the offending blue light. In this way normal after dark activities may continue using the remaining colors of light. The following figures illustrate the characteristics of such devices. Fig. 1 Plots of the relative intensity vs. wavelength of an uncoated (upper curve) and an identical coated lamp.

Figure 2. Eyeglass transmission spectrum.

In Fig. 1, plots of the relative light output vs. wavelength of an uncoated and an identical coated incandescent lamp are shown. Note that at wavelengths below 530nm the intensities of the coated lamp are well below those of an identical uncoated lamp. The transmission vs. wavelength of our eyeglasses is shown in Fig. 2. Note that below 530nm the transmission coefficient is less than 0,01 while above 530nm it rises rapidly to about 0,9. These and other devices with similar characteristics may be used to help find solutions to several health related problems, as discussed briefly in the following sections.

2. SLEEP PROBLEMS

It is obvious, as evidenced by the large number of sleep aids that are advertised and prescribed, that many people suffer from poor sleep habits. We have begun working with a sleep disorder specialist [4] who, in her own words, has seen “remarkable improvements” in the sleep of patients who are using our eyeglasses. Her patients, as well a large number of others who have used the eyeglasses, put them on one to two hours before bedtime. They also completely avoid exposing their eyes to unfiltered light before retiring in a well darkened room. Prior to retiring they are able to read, watch television, work on their computer, or take part in almost any after dark activity. Most of her patients, as well other users, report substantial improvement in their sleep habits after doing this for only three or four days. The assumption is that the start of the flow of melatonin is advanced in time [5], resulting in its being present in quantity at bedtime. This causes sleep to come quickly and deeply.

Studies have shown that sighted subjects kept in darkness and most blind people (effectively always in darkness) produce melatonin for 9 to 10 hours a night [6]. By wearing blue blocking eyeglasses for a few hours before bedtime and being in the dark while sleeping, the 9 to 10 hours of melatonin flow may be achieved by anyone. This means the flow of melatonin can continue for the full duration of sleep despite the fact that it started sooner. This results in sound sleep lasting throughout the night.

3. SLEEPY STUDENT SYNDROME

Studies have shown that because of the early starting times of many high schools, many students are barely awake during the first classes [7]. Relatively large levels of melatonin, the sleep hormone, have been found in the blood of such students during the early morning. This may explain their inability to perform well.

This problem may be avoided by advancing the time when melatonin production begins. This is accomplished by preventing exposure of the students’ eyes to blue light a few hours before their frequently late bedtime. Several ways exist that can accomplish this goal. The most convenient is for the students to put on blue blocking eyeglasses such as ours. Alternatively the lighting may be changed to coated light bulbs. In the latter case, however, other sources of light such as TV and computer screens, need to be covered with filters that block blue light.

Within a few days of avoiding blue light after 8 or 9 P.M., the students’ melatonin production cycle will be advanced so that it is completed well before the start of school. The advance may be solidified by exposing the students’ eyes to bright light containing substantial blue light soon after waking in the morning. However, the use of only the light in the morning is not encouraged, since having melatonin present in the evening will encourage the students to go to sleep (which they need), and also possibly provide protection from the risk of cancer [8].

4. BIPOLAR DISORDER

The combination of recent theorizing and results of clinical research studies has suggested a new approach to treating bipolar disorder. First, some have theorized that the root of the problem of bipolar disorder is the failure of the internal (circadian) clock to function normally. Melatonin production is controlled by the internal clock(s) but melatonin also helps to set the clocks via a feed-back process. Second, remarkable success has been obtained in treating bipolar disorder by subjecting patients to prolonged periods of darkness [9,10]. Third, as first clearly demonstrated [11], the use of goggles that block blue light is equivalent to exposure to darkness, as far as melatonin production is concerned]. With these three somewhat disparate factors in mind, a new form of treatment of bipolar disorder has been proposed and is under early testing [12].

Basically, the new treatment consists of having the patients initially wear blue blocking eyeglasses for a prolonged period, such that the time wearing them plus the time spent in darkness while sleeping exceeds 12 hours. The patients will be directed to develop a routine of going to sleep at a regular hour and awakening at a regular hour. For example, in the evening, the patients will put on the eyeglasses at about 7P.M. and go to bed in darkness at about 11:00 P.M. Soon after awakening at 7 A.M, exposure to bright light (preferable outdoors) will be encouraged. Obviously these times may be adjusted to fit the desired schedule of each patient.

As indicated in the previous two sections, the patients should avoid exposing their eyes during the night to light containing a blue component. Nightlights, such as coated incandescents or amber LEDs, should be used. The patients should avoid napping during the day and evening. Exposure to bright light (outdoors if possible) during periods of drowsiness is recommended. For the first week or two a low dose (3mg) of melatonin may be taken by mouth an hour or two before bedtime to help lock in the new setting of the internal clock. It is not necessary that the patients sleep the entire 8 hours as long as they stay in darkness or avoid blue light during that period. It may require several day for the internal clock to become well synchronized. Until then, the outlined schedule should be carefully followed. Once a patient’s clock is working properly, missing some part of the routine now and then should not be a problem. To verify that the clock is functioning properly, saliva samples may be taken at regular intervals for at least a 24 hours period, especially right before bedtime, upon awakening, and during the night if the patient awakens.

5. CANCER RISK

There is a considerable body of knowledge [8] showing that using artificial light at night may increase the risk of cancer. This reduces the time spent in darkness and thus reduces the time that cancer fighting melatonin is produced.. Studies have shown that blind people have a lower cancer rate than sighted people [12[. As already mentioned, other studies have shown that blind people and sighted people kept in darkness produce melatonin for 9 or 10 hours a night [6]. Typically, people in industrialized countries are in darkness and produce melatonin for only 6 or 7 hours a night. The various techniques discussed in previous sections can increase the duration of the melatonin flow to the natural 9 to 10 hours, but without a major change in life style. Though it will take many years to establish that using these techniques may reduce the risk of breast and other cancers, it would seem well worthwhile to do begin such studies as soon as possible.

6. CONCLUSION

Assuming that 9 to 10 hours of melatonin production may be required to solve a number of prevalent health problems, requiring people to spend 9 or 10 hours in darkness is not practical. The most convenient and simple way to accomplish this is to put on eyeglasses that block the blue light two or three hours before bedtime and to avoid exposing the eyes to blue light any time before arising. Night lights that either produce no blue light, e.g. amber LEDs, or filtered incandescent or fluorescent lamps for use in hallways and bathrooms, are recommended. As an alternative to wearing eyeglasses, the area where one spends the hours before bedtime should be equipped with lamps that do not produce the damaging blue light and blue blocking filters for TV and computer screens should be employed. Normal after dark activities may be conducted since the light remaining after removing the melatonin suppressing blue wavelengths can be made perfectly adequate for reading, watching television or working on a computer.

References

1. CZEISLER, CA and WRIGHT, KP Jr., Influence of light on circadian rhythmicity in humans, Regulation of Sleep and Circadian Rhythms, ed: Turek F.W. & Zee P.C. New York: Marcel Dekker, 1999.
2. BRAINARD, GC, HANIFIN, JP, GREESON, JM, BYRNE, B, GLICKMAN, G, GERNER, E, and   ROLLAG, MD, Action spectrum for melatonin regulation in humans: evidence for a novel circadian photoreceptor, J. Neurosci., 16, 6405-6412, 2001.
3. THAPAN, K, ARENDT, J, and SKENE, DJ, An action spectrum for melatonin suppression: evidence for a novel non-rod, non-cone photoreceptor system in humans, J Physiol .535, 261-267, 2001.
4. Personal communication: Berta Briones, M.D., see “A Sleep Disorders Reference for Physicians”, [email protected]..
5. SANTHI, N, DUFFY, JF, HOROWITZ, TS, and CZEISLER, CA, Scheduling of sleep/darkness affects the circadian phase of night shift workers, Neurosci. Lett.384, 316-320, 2005.
6. KLERMAN, EB, ZEITZER, JM, KHALSA, SB and CZEISLER, CA, Absence of an increase in the duration of the circadian melatonin secretory episode in totally blind human subjects, J. Clin. Endocrinol. Metab., 86 3166-3170, 2001.
7. CARSKAADON, MA, WOLFSON, AR, ACEBO, C, TZISCHINSKY, O, and SEIFER, R, Adolescent sleep patterns, circadian timing, and sleepiness at a transition to early school days, Sleep, 21, 871-881, 1998.
8. JASSER, SA, BLASK, DE, BRAINARD, GC, Light during darkness and cancer: relationships in circadian photoreception and tumor biology, Cancer Causes and Control, 4, 515-523, 2006.
9. WEHR, TA, TURNER, EH, SHIMADA, JM, LOWE. CH, BARKER, C. and LEIBENLUFT, E, Treatment of rapidly cycling bipolar patient by using extended bed rest and darkness to stabalize the timing and duration of sleep, Biol. Psychiatry, 43, 822-828, 1998.
10. BARBINI, B, BENEDETTI, F, COLOMBO, C, BERNASCONI, A, CIGALA-FULGOSI, M, FLORITA, M, and SMERALDI, E, Dark therapy for mania: a pilot study, Bipolar Disord., 1, 98-101, 2005.
11. KAYUMOV, L, CASSPER, RF, HAWA, RF, PERLMAN, B, CHUNG, SA, SOKALASKY, S, and SHAPIRO, CM, Blocking low-wavelength light prevents nocturnal melatonin suppression with no adverse effect on performance during simulated shift work, J. Clin. Endocrinol Metab., 90, 2755-2761, 2005.
12. Personal Communication: James Phelps, MD. See “Dark Therapy for Rapid Cycling and Mania” in www.psycheducation.org.
13. HAHN, RA, . Profound bilateral blindness and the incidence of breast cancer, Epidemiology, 3, 208-210, 1991.

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E.F. Carome, R.L. Hansler and V.E. Kubulins

Lighting Innovations Institute

John Carroll University

20700 North Park Blvd.

Cleveland, Ohio 44118, USA

[email protected]