OHSU Scientists Successfully Regulate Body Clocks in Blind Patients

10/12/00    Portland, Ore.

Research Printed in The New England Journal of Medicine.

For those without sight, sleepless nights are not uncommon. The human body utilizes sunlight to regulate its own internal body clock and signal the brain when it is time to rest. But for those who remain in perpetual darkness, like some of the visually impaired, the body clock tends to drift later each day. The result is recurrent insomnia and daytime sleepiness. Now researchers at Oregon Health Sciences University have found a way to reset the body clocks in blind patients, allowing them to sleep on the same schedule as the rest of the world. The research is printed in the Oct. 12 edition of The New England Journal of Medicine.

For most sighted people, the body clock runs on a 24-hour cycle. However, for most of those without any light perception, the body clock shifts daily. In fact, the average shift in a blind person is one-half hour per day. This condition, called free-running circadian rhythms, results in irregular sleep patterns. At times, the body clock in a totally blind person signals them to sleep at night. At other times, their body clock tells them to sleep during the day.

In an attempt to regulate sleep patterns for patients with free-running circadian rhythms, scientists at OHSU utilized melatonin, a hormone linked to the presence of sunlight. Specifically, scientists believe that melatonin signals the beginning of the biological night in the body.

For this study, seven totally blind subjects were given 10 milligrams of melatonin nightly, one hour before bedtime. This resulted in improved to complete sleep regulation in six of the subjects. Researchers then reduced the melatonin dosage gradually to 0.5 milligrams. This lower dosage proved sufficient in maintaining normalized circadian rhythms.

"Currently there are about 2 million Americans who are visually impaired," said Robert Sack, M.D., director of the Sleep Disorders Medicine Program at OHSU and lead author of the study. "Approximately 200,000 of those people are completely blind and many have trouble sleeping due to free-running circadian rhythms. In addition to providing relief to blind patients with this problem, this research helps further explain the role that melatonin plays in the human body."

Melatonin has also been shown to help adjust sleep patterns in shift workers, air travelers and nightowls. Additional uses include the adjustment between daylight savings time and standard time, winter depression also known as seasonal affective disorder (SAD) and the "Monday blues."

This research was funded by the National Institute of Mental Health and the National Institute on Aging, both components of the National Institutes of Health.