Students are going to
sleep later and may be underperforming in class because they're not getting
enough bright light in the morning, researchers say. Better school lighting may
help.
Riding in school buses
in the early morning, then sitting in poorly lighted classrooms are the main
reasons students have trouble getting to sleep at night, according to new
research.
Teenagers, like
everyone else, need bright lights in the morning, particularly in the blue
wavelengths, to synchronize their inner, circadian rhythms with nature's cycles
of day and night.
If they are deprived
of blue light during the morning, they go to sleep an average of six minutes
later each night, until their bodies are completely out of sync with the school
day, researchers from Rensselaer Polytechnic Institute reported Tuesday in the
journal Neuroendocrinology Letters.
The finding was made
by fitting a group of students with goggles that blocked blue light and
discovering that their circadian rhythms were significantly affected.
"These
morning-light-deprived teenagers are going to bed later, getting less sleep and
possibly underperforming on standardized tests," said lead author Mariana
G. Figueiro, a sleep researcher at the institute's Lighting Research Center.
"We are starting to call this the 'teenage night owl syndrome.' "
"This is a nice
little preliminary study" that definitely needs to be replicated, said sleep
researcher Mary A. Carskadon of Brown University, who was not involved in the
research. "I think the big take-home message probably is that better
lighting in the schools is a good idea."
Parents and teachers
have been complaining loudly in recent years that teens stay up too late at
night, then fall asleep in class the next morning and do poorly in school. The
new findings provide a possible explanation for the problem.
At the root of the
research is the circadian rhythm, the body's natural sleep and waking cycle.
Even though the Earth makes a full rotation in 24 hours, the body's circadian
cycle is about 24 hours and six minutes long. The cycle is mediated by a
chemical called melatonin. The body starts to produce it about two hours before
it is time to fall asleep and, in the absence of light, melatonin is released
about six minutes later each day.
That is why people in
dark rooms, caves or other locations with no external time cues will fall
asleep about six minutes later each day, so that their sleep-wake cycles slowly
drift in and out of alignment with the outside world.
In the study, Figueiro
and Mark Rea, director of the Lighting Research Center, studied 11 students at
Smith Middle School in Chapel Hill, N.C., which was designed so that a lot of sunlight
reaches classrooms.
On a Friday night, the
researchers measured what time the 11 students' bodies began releasing
melatonin. On Monday morning, the students were sent to school with orange
goggles that blocked most blue light from their eyes to mimic the conditions
found in many -- if not most -- schools.
By the end of the
week, the students were releasing melatonin 30 minutes later in the evening --
an average of six minutes per day -- and going to sleep correspondingly later.
"This is our
first field study," Figueiro said. "We would like to replicate it in
larger studies. Also for longer periods of time. We would also like to
determine if you can see an impact on performance."
If the findings are
replicated, a variety of solutions are available. Ideally, new schools would be
built to allow more natural sunlight into the classrooms. Students could also
be exposed to more sunlight outside.
Incandescent lights
should never be used in classrooms because "they are heavy on yellow and
red, and the circadian system is not tuned to those colors," Figueiro
said. "You want incandescent light sources in the evening."
Some fluorescent
lights are also not very good. Most that are currently used produce orange or
reddish light, but it is now possible to buy bulbs that emit more blue.