Is your teenager staring at some form of a screen late into the evening? If so, she might be disrupting her sleep patterns. While most teens stay up late, a study found that the amount and timing of morning light can alter a child’s natural nighttime sleep cycle.

Lack of exposure to morning light combined with getting A.M. rays at the wrong time of day can lead to nighttime sleep issues in teens, a group already running low on zzz’s. Adequate exposure to blue light waves (morning light) may however, reset natural sleep cycles.

Teen Circadian Rhythm Disrupted By Light Issues

Teenagers today have become near cave dwellers, spending less time in the sunlight than ever before. And for many, this means having a hard time falling asleep at night.

Insufficient morning light and exposure too soon, researchers found, confuses the body’s internal alarm clock. In response, the brain can’t stimulate its 24-hour biological system, a natural rhythm designed to modulate the sleep/wake cycle. And in teens, a group already inclined to stay up too late, when their internal body clock gets out of sync, even when they are ready to call it a night, sleep may not come so easily.

“These morning-light-deprived teenagers are going to bed later, getting less sleep and possibly under-performing on standardized tests. We are starting to call this the teenage night owl syndrome,” says Mariana Figueiro, Ph.D., Assistant Professor and Program Director at Rensselaer Polytechnic Institute’s Lighting Research Center (LRC) and lead researcher on the new study.

In the study researchers found that 8th grade students who wore special glasses to prevent short-wavelength (blue) morning light from reaching their eyes experienced a 30-minute delay in sleep onset by the end of the five-day study.

“If you remove blue light in the morning, it delays the onset of melatonin, the hormone that indicates to the body when it’s nighttime,” explains Dr. Figueiro. “Our study shows melatonin onset was delayed by about six minutes each day the teens were restricted from blue light. Sleep onset typically occurs about two hours after melatonin onset,” says Figueiro.

The colors of the light spectrum affect the body’s rhythm in various ways, particularly regarding sleep patterns. Daylight is mainly comprised of short, visible wavelengths of light that provides a blue visual sensation, such as the blue sky. How bright the light is, how far away, the duration of exposure, and when someone is exposed to specific light waves, impacts sleep patterns.

People are more likely to sleep deeply in the late hours of night when their body temperature drops, and to awaken when their body temperature begins to rise, usually between 6 AM and 8 AM. As people age, their brain’s “pacemaker” loses cells, changing circadian rhythms, especially sleep patterns. As a result, the elderly nap more frequently, have disrupted sleep and awaken earlier.

Sleep, Melatonin and Biological Cycles

Melatonin, a hormone produced in the brain by the pineal gland, is created from the amino acid tryptophan. The creation and release of melatonin is stimulated by darkness and suppressed by light. Melatonin, researchers believe, is involved in circadian rhythm and the regulation of a wide variety of body functions including sleep.

Circadian rhythms are biological cycles in the body that repeat approximately every 24 hours, and include the sleep/wake cycle, body temperature, hormone levels, heart rate, blood pressure and pain threshold.

The brain’s internal pacemaker determines when nerve cells should fire to set the body’s rhythms. While adults generally produce melatonin around 10pm, teenagers, according to a study cited in an online British Broadcasting Corporation (BBC) article, were found to begin producing melatonin around 1am. Whether this is in response to puberty or caused by teens’ nighttime behavior is hard to say.

The delay in melatonin production could be the result of teenagers playing computer games and watching television till the wee hours. Both screen activities stimulate the brain, exposing it to bright light that holds off the release of melatonin. The hormonal flux of puberty, however, may be the culprit, postponing the body’s nightly release of melatonin. Either way, sleep releases a critical hormone involved in growth spurts. Teens need more sleep than both children and adults, yet often they get less.

Regulating Sleep Patterns in Teens

Researchers involved in the light study developed a way to reset the internal “master clock” in teens and the elderly. The process involves blocking blue light at certain times by wearing orange glasses, followed by exposure to blue light and darkness at nighttime.

The key to resetting the body clock is mimicking a distinct repetitive pattern of light and dark. Figueiro explains that when a teenager gets up and waits outside for their bus in the morning light before their body is ready for the blue light cycle, their internal body clock becomes confused. Their alarm clock might say 7am, but their body clock senses it’s earlier. In the study, the teens wore the special blue light blocking glasses when they woke up.

Later in the morning after their minimum core body temperature was reached, the subjects were able to naturally reset their internal clocks by being out in the morning light (e.g. at the bus stop).

Teen Light Study and Implications for School Design

Over the years, Dr. Figueiro has repeatedly heard from parents concerned their teens were sleep deprived. As a result of the findings from the study, she suggests addressing two key questions: How to promote exposure to morning light with teens and how to design schools differently.

Giving students a quick mid-morning break to go outside and putting blue LEDs around computer screens in classrooms are two ways, Dr. Figueiro offers, to address the issue in schools. Exposing teens with delayed nighttime sleep issues to adequate amounts of morning light at the appropriate time during the day may reset their internal body clock and naturally modulate their sleep cycle.

References:

Chang AM, Reid KJ, Gourineni R, Zee PC, ”Sleep timing and circadian phase in delayed sleep phase syndrome,” J Biol Rhythms. 2009 Aug;24(4):313-21.

MedlinePlus [Internet]. Bethesda (MD): National Library of Medicine (US); Melatonin; [updated 2009 Aug 25], Accessed May 6, 2010. “Late Nights and Laziness,” British Broadcasting Corporation Online, Accessed May 6, 2010.

Copyright Laura Owens. Contact the author to obtain permission for republication.

 

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