Bright light in measured doses can reset the body's biological clock, promising possible relief for jet lag, sleeping disorders or night-to-day shift changes, researchers at Brigham and Women's Hospital said yesterday.
In a study that started out as a Harvard student's independent biology project, Medical School doctors monitored light-induced changes in an elderly woman's sleeping and waking patterns for 114 days.
Although only one subject was involved in this study, the project did provide new evidence of what affects a person's circadian pacemaker, the part of the brain that sets the biological clock, coordinating hormone and chemical changes with the external environment, according to Charles A. Czeisler, the study's primary investigator and an assistant professor of biology.
An older person was chosen for this study because she normally followed a regular sleeping-waking schedule, and because her system was most susceptible to light during the evening hours, unlike those of younger people, who react most strongly in the middle of the night, said Czeisler, who co-authored the study appearing today in the journal Science.
He added that conclusions drawn from this single case would need to be confirmed by future studies. "More research must be conducted on younger subjects in order to discover normal response rates to bright light exposure," said James Allan '86, Czeisler's assistant, whose project inspired the study.
Possible applications of this discovery are still being explored, but it provides information valuable to scientists, said Czeisler.
"Some day we may be able to install bright lights in factories so workers on rotating shifts could get therapeutic doses of bright light on their evening shifts to reset their internal clocks in preparation for the next week's rotation to the night shift," Czeisler said.
Allan said workers whose shifts change frequently have a high rate of cardiovascular problems, and that women with irregular schedules have a higher rate of miscarriages. Bright light treatments may eventually help alleviate these problems, said Allan.