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Photo of Scott Campbell Photo of Patricia Murphy Scott Campbell and Patricia Murphy as seen on
Life's Little Questions: Can You Beat Jet Lag?

Click on Scott or Patricia's photo to read a brief bio.

q I have learned about phototherapy for SAD through psychology courses I am currently taking. I am curious if you have found any difference in the use of sunlight, incandescent light, full spectrum light, or the blue lights you use. Is the type of light you need to use for resetting a person's clock dependent on the type of light, the amount and time used, or a combination of the two? Ryan

A (from Scott Campbell) Factors involved in resetting the biological clock probably include duration of exposure, composition (wavelength) of the light, and brightness. In general, broadband white light is best for ocular exposure, whereas light in the blue and blue-green portion of the spectrum is probably best for extraocular exposure. Although additional research needs to be done to establish exact relationships, there is a general feeling among experts in the field that the brighter the light, the shorter the duration of exposure is required. So, for example, some therapists recommend daily exposure of 2 hours of light with an intensity of 2500 lux for the treatment of SAD, whereas others prescribe a half-hour of light with an intensity of 10,000 lux.

q Where can I learn more about the latest developments and findings that research such as yours is discovering? (asked by many viewers)

A Most of this type of research is published in scientific journals that usually can't be found at your corner newsstand. However, if you have access to a university library, most subscribe to a number of such journals. In addition, if you have access to the world wide web, there are a number of sites that provide a wide array of information concerning biological rhythms, sleep, light, and so on. The following key words may be useful in locating such sites via your search engine: "circadian rhythms", "body clock", "sleep", "biological timing", "light", "seasonal affective disorder", "insomnia".

q Is jet lag a more serious problem for older people than it is for younger people? Ally and Laci

A (From Scott Campbell) Jet lag affects people to varying degrees, and many of the factors are still unknown that cause one person to suffer tremendously and another person to feel no ill effects from transmeridian travel. However, one factor that clearly affects one's ability to cope with jet lag is aging. As we grow older, our biological clocks seem to be less able to tolerate the resetting that is required by jet travel over several time zones. In the same way, it is more difficult for older people to cope with shift work. Their clock simply resist being reset, and therefore, it tends to take longer to readjust to the new time. In addition to the longer time required to adjust the older person's internal clock, it is likely that sleep is more severely disrupted, since older people tend to have more "fragile" sleep to begin with.

q In experimenting with the use of various kinds of light, have you ever wondered whether using other parts of the electromagnetic spectrum (not just visible light) might affect the pineal gland and cause changes in the production of melatonin, as well? If light pads behind one's knees can affect the pineal, what might happen when using, say, microwaves or radio frequencies? John

A (from Patricia Murphy) In our study of light exposure to the popliteal region behind the knees, we used the time at which melatonin levels increased during the nighttime hours as a marker of circadian phase. That is, our study showed an effect on the timing of melatonin release from the pineal gland (i.e., circadian effect), but we did not test whether this type of light exposure could alter the synthesis and release of melatonin production in the pineal gland (immediate effect).

However, in the vast literature concerning the effects of extraocular light on non-mammalian species, it is clear that the pineal gland, and melatonin, are not necessary for the circadian phase-shifting effects of extraocular light to occur.

Although the light source we used in our study was in the visible spectrum, it is of interest to examine whether particular frequencies of the light might be primarily responsible for the phase-shifting effect.

In regard to how non-visible frequencies might affect pineal output, there is in fact, evidence that electromagnetic frequencies can alter melatonin levels. We have not yet studied whether microwaves or radio frequencies can impact the circadian timing system, but whether non-visible parts of the electromagnetic spectrum can affect physiology is certainly an important question.

q I'm wondering if your light application techniques can help those people with narcolepsy? If narcolepsy is caused by the brain not going into a deep sleep, thus not fully recharging a person's "batteries," could light application reset a narcoleptics biological clock? (This would be a wonderful alternative to taking medical drugs, which don't always work for narcoleptics anyway!) Shari

A (from Patricia Murphy) There is every reason to believe that extraocular light could reset the biological clocks of people with narcolepsy. However, the effects of extraocular light on either "normal" sleep, or in people with sleep disorders, have not yet been tested. I agree with you completely -- it would be of great interest to find alternative treatments for narcolepsy, especially non-pharmacological treatments such as light therapy. While ocular light therapy has been used successfully for the treatment of certain types of sleep problems that involve the biological clock, it is yet too early to say whether extraocular light can help individuals with either these or other types of sleep difficulties, such as narcolepsy.

q Are there any plans to use your idea to help shift workers? This seems like a much better opportunity than dealing with the temporary discomfort of jet lag. Earl

A (From Scott Campbell) We agree that using light to reset the internal clocks of shift workers would be an ideal application for our findings. In fact, exposure to bright light through the eyes has been shown to be effective in helping workers adapt to rotating shift schedules, both in simulated laboratory studies and in the "real world ". NASA, for example, has employed light treatment to adjust the internal clocks of some of its ground crew during Space Shuttle flights (as well as the clocks of astronauts). We are currently working with several companies to implement non-ocular light exposure as an intervention for shift work difficulties.

q Would any of this light therapy that you're working on be useful in treating seasonal affective disorder? Don

A (From Scott Campbell) This very interesting possibility is one focus of ongoing research in several laboratories. People who suffer from Seasonal Affective Disorder (SAD) feel depressed at cetain times of the year, typically during the winter months. The long nights and short days of winter can definitely have an effect on mood in many people, and one treatment that has been used successfully in SAD patients is timed exposure to bright light. Although it is not yet clear exactly how light treatment improves the symptoms of SAD, there is growing evidence that the biological clock may be involved.

If the underlying causes of SAD include a malfunctioning internal clock, then we hope to be able to use extraocular light exposure to effectively treat SAD. One important drawback to light treatment is that it is time-consuming and sometimes inconvenient. If light behind the knees turns out to be an effective therapy for SAD, it may make it easier for some people to take advantage of this very effective non-drug treatment.

q Is there any way I can get those blue lights for the back of my knees? David

A (From Scott Campbell) The device that we used in our research was developed for the treatment of neonatal jaundice. Because it is a medical device, it is quite expensive. Perhaps more importantly, it needs to be kept in mind that timing is everything when it comes to light treatment. If a person's light exposure schedule is off by as little as 1 hour, his or her biological clock can be reset in the wrong direction. The result can be even worse sleep and poorer waking performance than if he or she had done nothing at all. So, unless one knows where one's internal clock is set, and when to get light in relation to that internal clock setting, self-treatment can be troublesome. For these reasons, we suggest that do-it-yourself clock resetting not be attempted.

q I was fascinated by your light experiments. Do people who are totally blind have a natural daily biological cycle? If they do, how is it regulated? There just aren't any unrelated questions! Bob

A (From Patricia Murphy) Yes, blind individuals have a circadian timing system -- a biological clock -- in the brain, as do all humans, and indeed, all animals studied. In some (about 50%) blind individuals who cannot perceive the daily light-dark cycle, the internal biological clock may take over, and the blind person's circadian rhythms "free-run." This is the same thing that happens when a person is studied in time isolation, in a room without windows or clocks or any other cues to time of day. Humans tend to "free-run" at a period of slightly greater than 24 hours. Thus, when a blind person is "free-running," he will typically go to sleep and wake up at a later clock time each day; eventually his bedtimes and waketimes cycle around the clock. This is not a problem when he is going to bed and waking up at times that the rest of society is, but may be very difficult at times when he is tired during the middle of the day and is awake during the nighttime hours. This circadian rhythm sleep disorder is more prevalent in blind persons than in sighted individuals, but there are also reports of people with normal vision who "free-run" in society. Although it is clear that the daily alternation of light and darkness is the most important cue by which our internal clock gets "set," there are also many blind individuals, without light perception, who do not "free-run." It appears that their internal clocks may be set by time cues other than light, such as social cues (mealtimes, daily routines, etc.). We have designed a study to examine whether extraocular light exposure can be used to alter circadian phase in blind individuals, and perhaps can reset their clocks and improve their sleep patterns.

q When you put the light on the back of the persons knee's, won't the light burn that persons skin after three hours? Traci

A (From Patricia Murphy) The light source we used was a fiber optic pad, which gives off no heat, and therefore remains cool over time. In fact, the device we used, called a Biliblanket (Ohmeda Inc.), is typically used to treat neonatal jaundice. An infant with jaundice is laid directly on top of the pad (the light causes bilirubin to be released from hemoglobin in the blood, and the baby urinates the excess hemoglobin out of her system, curing the jaundice).

Please!!! We want to make sure that people don't try to reset their clocks using any type of light that could damage their skin!


Scientific American Frontiers
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