PEOPLE who are totally blind don’t sleep too well at night. Their body clocks
go awry because they can’t sense any light, so they can’t tell night from day.
Now researchers have found a treatment: the anti-jet-lag hormone, melatonin.
“Light is the major time cue in humans,” says Debra Skene of the University
of Surrey in Guildford. In sighted people with normal body clocks, levels of
melatonin in the blood peak at around 4 am. In totally blind people, melatonin
peaks at a different time each day. Their sleep suffers, so they often nap
during the day to compensate for their disturbed nights.
Skene wondered if the body clock of completely blind people could be reset
with daily doses of melatonin. In an experiment on seven totally blind
volunteers with severe sleep disruption, she found that the melatonin treatment
gave most a better night’s sleep, with fewer daytime naps.
Advertisement
Later she found that the treatment only reset the clock if it was timed
correctly in relation to the subject’s own melatonin peak. “Melatonin can work,
but we need to know the status of the clock before we begin treatment,” she
says.