Irregular Sleep Patterns of
Teenagers Linked To Morning Light
Lack of the right light each morning to reset the body's natural
sleep clock might play a role in teenagers' irregular sleep, a small
but provocative school experiment suggests.
Specialists say too few teens get the recommended nine hours
of sleep a night. They are often unable to fall asleep until late
and struggle to awaken for early classes. Sleep patterns start
changing in adolescence for numerous reasons, including hormonal
changes and more school, work and social demands.
Researchers turned to a North Carolina school built for energy
efficiency, with lots of skylights so classrooms could reduce
use of electric lights yet still be brighter than usual indoors.
That allowed testing of the effects when some eighth-graders at
Smith Middle School in Chapel Hill suddenly lost exposure to a
specific wavelength of light.
From waking until school ended, 11 students donned special orange
goggles that block short-wavelength ``blue light,'' but not other
wavelengths necessary for proper vision. Blocking that light for
five days upset the students' internal body clocks _ delaying
by half an hour their evening surge of a hormone called melatonin
that helps induce sleep, Rensselaer Polytechnic Institute researchers
Teens who trudge to the bus stop before dawn or spend their days
in mostly windowless schools probably suffer the same effect,
as daylight is the best source of those short-wavelength rays,
said lead researcher Mariana Figueiro of Rensselaer's Lighting
``If you have this morning light, that is a benefit to the teenagers,''
Figueiro's study was a first step to test in real-world conditions
findings from sleep laboratories showing that light effects on
the 24-hour body clock may play a role in teen sleep problems
The study, published in the journal Neuroendocrinology Letters
, is small and didn't track student sleep, just an early sign
of change, the evening melatonin surge that typically precedes
sleep by about two hours.
But while preliminary, the study is well done and should spur
additional research on everyday light exposure, said Dr. Judith
Owens, an associate pediatrics professor at Brown University and
sleep medicine specialist.
``There's a biologically based shift in the natural sleep onset
and wake-up time. I think what this study shows is that you can
impact that shift with light manipulation,'' Owens said. ``The
major take-home message is to get natural light exposure early
in the day.''
Morning light is not the only factor, added Figueiro. Tuesday's
report is part of a larger study involving a second school in
New York to examine evening light exposure computer and
TV light plus regular indoor lighting. Too much evening light
can add to the problem, she said.
The research was funded by the National Institutes of Health
and U.S. Green Building Council.
February 17, 2010