Study Pinpoints Sleep Clock

Most students are dimly aware that all-nighters aren't healthy. A recent Harvard study of circadian rhythms showed, among other findings, just how much they can throw a body off.

The study, published last week, showed that the body clock regulating sleep runs on a cycle about 24 hours and 11 minutes long--not 25 hours as scientists previously thought.

"If the clock had been 25 hours, than it means every day you're going to correct it an hour," said Richard E. Kronauer, a member of the Harvard-MIT division of health sciences and technology and a senior author of the study.

Subjects left their wristwatches at the door and lived for 28 days in an environment of subdued light. Cut off from normal activities such as work and school, study participants lived a 28-hour day as researchers studied their sleep patterns.

By taking measurements of body temperature and the body chemical melatonin, the scientists discovered that exposing the subjects to even dim light during nighttime hours can reset the human clock, making it difficult to wake up on time in the morning.

"The fact that we are that sensitive to light means that people have to be more careful about their daily schedules so they don't screw things up," Kronauer said.

The group studied included adults in their early twenties as well as elderly people. Harvard Medical School professor Dr. Charles A. Czeisler '74, the lead author of the study, said previous research indicated that many older people suffer from insomnia because the sleep cycle shortens with age.

"There was a lot of evidence that the [sleep cycle] sped up as we got older," Czeisler said. "We now know that that's probably not the case."

The study's findings have major implications for the field of sleep study, scientists said, and will hopefully pave the way for new cures for insomnia.