Two U.S. military supported studies find bright lights can improve alertness, reduce post-traumatic stress

A series of brief flashes of bright light is all it takes to improve alertness at night, as reported in a research abstract (#0257) presented Monday at SLEEP 2010.

Test subjects were wakened two hours after their typical bedtimes, brought into a dark room and were exposed to a two-millisecond light pulse once a minute for an hour.

Researchers at Stanford University noted a significant improvement in self-rated alertness and reaction time, as measured by the auditory Psychomotor Vigilance Test.

The subjects also spent an hour in darkness at a different time and date showed no improvements.

“We found it shocking that light exposure as brief as a few milliseconds could engender changes in alertness and brain wave activity,” said lead researcher Jamie M. Zeitzer, PhD. “These results change the manner in which we think about the brain’s capacity to respond to light.”

These findings could lead to a breakthrough for shift workers and military personnel, who are often required to go days without sleeping during wartime deployment.

Another study (# 0706) on display offers new hope for troops returning from battle with Post Traumatic Stress Disorder.

Researchers found bright light therapy greatly reduced the sleep disturbances specific to PTSD. The treatment also produced a moderate improvement in other PTSD symptoms and depression.

16 soldiers participated in the study after returning home to the U.S. from Afghanistan or Iraq with combat-related PTSD.

Half of the troops received 30 minutes a day of 10,000 lux bright light therapy for one month. The other half received a sham treatment as a placebo.

At the onset and immediately following treatment the soldiers were given the clinician-administered PTSD scale. The troops also completed weekly depression and sleep quality assessments.

Bright light therapy typically involves exposure to up to 10,000 lux of light for scheduled periods of 20 minutes or more. The technique can decrease sleepiness and improve alertness by suppressing the production of melatonin, a hormone that tells your body when its time to sleep.

Images courtesy the U.S. Army

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Green light also alters sleep, television before bed still bad

Sleep experts warn the bright light produced by televisions, computers and iPads can meddle with sleep. There’s a line of products made to counter that effect by blocking out blue light wavelengths, which can reset the body’s circadian clock. Online you can purchase special sunglasses and screen filters, but there’s no guarantee the products will work as advertised and prevent insomnia.

There’s new evidence that its not just blue wavelength light that alters the body’s circadian clock. Researchers at the Brigham and Women’s Hospital in Boston found the green light produced from those same sources has a similar effect.

More than a decade ago, scientists discovered there are special cells in the eye that contain the blue light-absorbing pigment melanopsin. When the eye detects blue light, it delays the body from secreting melatonin.

The authors of the new study wanted to see if the eye’s rods and cones, which respond to green light wavelengths, also contributed to the body’s circadian adjustment.

The researchers exposed a group of volunteers separately to blue and green light, both for several durations and intensities. The experiment happened in the evening, before the body naturally secretes melatonin. Scientists measured the subjects’ melatonin response in each condition.

At low intensity, there was very little difference in the body’s reaction to blue and green light wavelengths. However, blue light produced a greater effect over time and at higher intensities.

The authors suggest there’s room to improve light therapy for sleep disorders based on these findings. The treatment may be more effective if the light devices combined blue and green light.

The study may have potentially substantial implications for the field of sleep research.

AASM President Clete Kushida told USA Today “(the finding) sort of goes against what was believed before.”

He said researchers should explore the possibility that the full spectrum of light may affect the body clock.

For our readers who aren’t scientists, the study reinforces the notion that evening use of electronic screens can hinder sleep, and special sunglasses won’t help. We recommend shutting off the television or other bright electronic devices an hour before bedtime and picking up a book, or better yet, an e-reader.

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Teens & Delayed Sleep Phase Disorder

Some people have a circadian clock that makes them “evening types.” These “owls” have a natural tendency to stay up late at night and sleep late in the morning.

Children tend to become night owls as teens because of a shift in the timing of their circadian clocks. This change causes them to feel sleepy later at night. As a result they also prefer to wake up later in the morning.

But as CNN reported last week, some teens may have an extreme change in the timing of their body clock. They may be unable to fall asleep until late at night or early in the morning. Then they may want to sleep until later morning or early afternoon. This problem is called delayed sleep phase disorder.



Insomnia symptoms can be severe when a person with DSP tries to go to sleep at a “normal” time. Excessive daytime sleepiness also can occur when he or she has to wake up early in the morning.

Teens with DSP can have a hard time in school. It can be difficult for them to conform to an early morning school schedule.

But there are effective treatments for DSP. It can be treated by taking melatonin in the afternoon or early evening. Another option is to use bright light therapy in the morning.

Both treatments can help “re-set” the body clock of a person with DSP. This can help normalize the timing of sleep.

“The way to treat delayed sleep phase is give light, in particular blue light like the light in the sky,” AASM member Dr. Jeffrey Durmer told CNN. “It activates a part of the eye that activates a part of the brain that keeps the circadian rhythm under control.”

DSP treatment should be supervised by a board-certified sleep specialist. It is important to determine the proper timing and dose of treatment that is required.

Get help from a board-certified sleep specialist at an AASM-accredited sleep center near you.

Last month a study reported that teen sleep patterns may be disrupted by a lack of exposure to morning sunlight. The researchers proposed that the problem can be solved by designing better school buildings.

Read more about sleep and teens.

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Sleepy Teens Need to See the Light

A new study reports that teen sleep patterns may be disrupted by a lack of exposure to morning sunlight.

The study took place at a middle school in Chapel Hill, N.C., that has good daylight design. South-facing skylights allow plenty of natural light to enter nearly all spaces of the building.

Eleven eighth-grade students wore orange goggles for a five-day school week. The goggles prevented short-wavelength, “blue” light from reaching their eyes.

This light plays an important role in helping to set the body’s circadian clock. This timing system helps regulate sleep and wakefulness.

In the evenings the researchers measured the children’s “dim light melatonin onset.” This is the time when the body produces more melatonin.

This hormone is a “darkness signal” for the body. Sleep tends to occur about two hours after melatonin onset.

Results show that melatonin onset was delayed about six minutes per day. This added up to a delay of about 30 minutes by the end of the week.

The authors report that this delay may contribute to later sleep times and shorter sleep durations in teens. Early school start times may contribute to the problem by reducing exposure to morning sunlight.

“These morning-light-deprived teenagers are going to bed later, getting less sleep and possibly under-performing on standardized tests,” lead researcher Mariana Figueiro said in a news release. “We are starting to call this the teenage night owl syndrome.”

Figueiro added that the problem can be solved by designing better school buildings. One sponsor of the study was the U.S. Green Building Council.

“The situation in schools can be changed rapidly by the conscious delivery of daylight, which is saturated with short-wavelength, or blue, light,” she said. “Delivering daylight in schools may be a simple, non-pharmacological treatment for students to help them increase sleep duration.”

Figueiro is the program director of the Lighting Research Center at Rensselaer Polytechnic Institute in Troy, N.Y. At LRC they have created a small device called a “Daysimeter.” It measures a person’s exposure to short-wavelength, blue light.

Read more about sleep and teens.

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