Light Deprivation Hinders Ability To Regulate Sleep-Wake Cycle

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The amount of light exposure can have a profound effect on an individual's

sleep pattern. Stronger light intensity enables noradrenergic locus coeruleus

(LC) neurons, which regulate arousal, to function normally and, therefore,

provide a circadian regulation of the sleep-wake cycle. Light deprivation, on

the other hand, induces a loss of noradrenergic fibers which, in turn, throws a

person's sleep-wake rhythm out of kilter.

 

The study, conducted by Monica McGonzalez, PhD, and Gary Aston-Jones, PhD, of

the University of Pennsylvania, Philadelphia, focused on rats, that were

maintained on a light-dark (LD) schedule or in constant darkness (DD) for three

to four weeks, and treated with DSP-4, a neurotoxic agent specific for

noradrenergic-LC projections. Vigilance states were analyzed before and three

weeks after LC lesion. The DSP-4 lesion was verified by immunohistochemistry of

noradrenergic fibers in the frontal cortex.

 

" DSP-4 decreased the amplitude of the sleep-wake rhythm in LD animals by

significantly decreasing wakefulness and increasing sleep during the active

period, " the authors wrote. " However, DSP-4 had no effect on the sleep-wake

cycle of DD animals. Moreover, DD itself decreased the amplitude of the

sleep-wake cycle similar to that of the neurotoxic lesion of the noradrenergic

system in LD animals.

 

This study is particularly useful for those persons suffering from shift work, a

circadian rhythm sleep disorder that occurs due to a work schedule that takes

place during the normal sleep period. This schedule requires you to work when

your body wants to sleep. Then you have to try to sleep when your body expects

to be awake. The timing of when you sleep and wake is greatly different to your

internal body clocks' expectations.

 

This sleep problem causes you to have trouble sleeping or to be severely tired.

It is most often reported due to the night and early-morning shifts. These

workers typically sleep one to four hours less than average. They also feel that

the quality of their sleep is very poor. They do not feel refreshed when they

wake up. This can hinder their performance at work. It can also make them less

alert. This can put them at risk of an injury on the job.

 

One of the ways to cope with working an overnight shift is to adjust the

lighting of your work space. Intense light exposure will enable your body to

adjust to the " daytime-like " conditions in your office, and make you more alert

and effective at your job. When it's time for you to go to sleep, take the steps

necessary to make your bedroom dark. This will train your body to go to sleep at

a bright time of day.

 

Sleep problems from shift work affect male and female workers of all age groups.

Those who have unusual work hours are most likely to have it. Estimates are that

two-to-five percent of the general population is affected, not including people

who work early-morning shifts.

 

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Sleep is the official journal of the Associated Professional Sleep Societies,

LLC, a joint venture of the American Academy of Sleep Medicine and the Sleep

Research Society.

 

SleepEducation.com, a Web site maintained by the AASM, provides information

about the various sleep disorders that exist, the forms of treatment available,

recent news on the topic of sleep, sleep studies that have been conducted and a

listing of sleep facilities.

 

Source: October 1st issue of the journal Sleep

 

For further information please go to:

American Academy of Sleep Medicine

 

 

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