Setting the Body Clock in the Dark

From the WebMD Archives

Oct. 11, 2000 -- Are you a morning lark or a night owl? If you're feeling wide awake when everyone else is sleeping, new research on sleep disorders in blind people, reported in the Oct. 12 issue of TheNew England Journal of Medicine, may help you get back in sync.

"This is an important study, which confirms and extends previous research by both U.S. and European authors," Derk-Jan Dijk, PhD, tells WebMD. "It illustrates the importance of the biological clock in sleep-wake regulation, and shows that 'treating' the clock can 'treat' some sleep disorders." Dijk, who is a chronobiologist at the University of Surrey in Guildford, England, was not involved in the study.

Normally, our body clock is set for a cycle slightly longer than 24 hours, which is why we tend to sleep later each morning, then go to bed later each night if we have time off and don't set the alarm. But the 24-hour cycle of daylight and darkness tends to get us back on track.

"People must be able to perceive light through their eyes in order to synchronize their body clocks to the 24-hour day," researcher Alfred J. Lewy, MD, PhD, tells WebMD. "Blind people drift later each day. When their clocks are reversed, telling them to sleep during the day and stay up at night, they have insomnia and daytime sleepiness," says Lewy, director of the Sleep and Mood Disorders Laboratory at Oregon Health Sciences University in Portland.

"Blind people are under constant jet lag," Sato Honma, MD, PhD, tells WebMD. He's an associate professor of medicine at Hokkaido University in Sapporo, Japan, and was not involved in the study.

In Lewy's study, seven totally blind subjects with sleep disturbances were given either melatonin or a sugar pill one hour before their preferred bedtime for several weeks. After their sleep patterns were recorded, each patient was switched over to the other treatment. Neither the patients nor the nurses knew which medication was being given.

Before treatment and while taking the sugar pill, all seven subjects had sleep problems related to an abnormal daily cycle. Most of them had a cycle longer than 24 hours, and on average, they were about half an hour off. While taking melatonin, six subjects slept better, and their wake-sleep cycle normalized to 24 hours. Three of them continued taking melatonin for three months and continued to sleep well even though the dose was gradually reduced.

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"Even on small doses of melatonin, the sleep pattern remained normal," James E. Jan, MD, tells WebMD. "This study has great clinical importance for those unfortunate blind individuals who suffer from this severe, chronic sleep disorder throughout their lives," says Jan, director of the visually impaired program at the British Columbia's Children's Hospital in Vancouver, British Columbia. He was not involved in the study.

Of approximately two million legally blind people in the U.S., about 200,000 may have a sleep disorder "that for some is the second most burdensome aspect of being blind," Lewy says.

Blind study participants offer a unique opportunity to researchers "because their lack of light input allows us to study the basic physiology of the body clock unperturbed by the light/dark cycle," says Lewy. "What we learn about their clocks we can generalize to sighted people."

Sleep disorders in sighted people that may respond to melatonin include jet lag, "Monday blues," and seasonal affective disorder, or depression related to less daylight in winter. Melatonin may regulate sleep in these conditions by setting the body clock back to normal. It may even correct sleep problems related to working night shifts or adjusting between daylight-saving time and standard time.

Melatonin has been widely used as a nutritional supplement without any reports of serious side effects, and this study shows that even very low doses can be helpful. However, patients first starting melatonin for sleep disorders may need higher doses, which should be supervised by a physician, Lewy explains.

"We still do not know the side effects of chronic or lifetime melatonin [use]," Honma says.

For all you morning larks who bounce out of bed when the whole house is still snoring, or for you night owls pacing the halls when everyone else has gone to bed, melatonin might be something to consider. As with all nutritional supplements, caution and good judgment are needed, and melatonin may not work for everyone.

"About 10% to 15% of patients taking melatonin to induce sleep may actually feel more awake than before," warns George A. Bubenik, MD, associate professor of zoology at the University of Guelph in Guelph, Ontario.

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