The Effects of Acute vs. Chronic of Screen Illumination on: Sleep Efficacy and Architecture, Physiology, Emotion and Behavior: Possible Effect on Human Health
Condition: Sleep; Emotion
Study type: Interventional

Summary: 
      The human eye has a dual role, which is reflected by the various photo-receptors used for
      vision of images and colors ,Image forming photoreceptors (IFP) and for entrainment of our
      "Biological clock" located in the hypothalamus through the retinal ganglions known as
      non-image forming photoreceptors (NIFP). The recently discovered new photo-pigment melanopsin
      which is sensitive to short wavelength (SWL) illumination exists in the-NIFP. The axons of
      the NIFP form a special nerve known as the Retino-hypothalamic-tract (RHT) that transfers the
      SWL signal to the biological clock resulting in suppression of pineal melatonin (MLT)
      production. This is the basic mechanism by which environmental light/dark cycles entrain the
      biological clock and transfer the message to organs, tissues and cell.

      The American Medical Association (AMA) issued a resolution in 2012 stating that light at
      night constitutes environmental pollution because it violates the daily cycles, including the
      waking and sleeping cycles, and suppresses the secretion of melatonin from the pineal gland
      at night. Results of other studies have shown that exposure to artificial light at night
      (ALAN) and mainly those emerging from SWL sources suppresses MLT-produced in the pineal
      gland. Computers, tablets, TVs, and smart-phones screens emit SWL illumination, during the
      day and night hours, whether as active or passive users. The results of previous studies show
      that, exposure to SWL-ALAN illumination suppresses MLT-secretion and disrupts sleep patterns.
      In order to understand better the effect of SWL-exposure emerging from screens on human
      behavior and health, the investigators will study the effects of SWL-exposure on the
      structure and quality of sleep, cognitive functioning in Continous Performance Test (CPT
      III), emotional state, and physiological, variables (melatonin secretion levels and body
      temperature) that were not tested in previous studies.
    

Detailed description: 
      The investigators will examine whether there is a difference between one-time and multiple
      exposures to computer screen lighting (350 lux). The investigators hypothesize that multiple
      and continuous exposure will have a more significant detrimental effect on the quality of
      sleep and consequently on performance, emotional, and physiological indicators, than one-time
      exposure to screen light.

      Procedure:

      On the base-line, first and fifth night of the study, at the end of two hours of exposure to
      screen light, the subject will be connected to the sleep test system by a skilled technician.
      On all other nights (nights 2-4), exposure to computer light only, will be conducted and at
      the end of the exposure the subject will be asked to go to sleep. During the entire
      experimental period the subject will wear an Actigraph watch to ensure regular sleeping
      hours. In addition, subjects will be asked not to expose themselves to a
      computer/tablet/smartphone screen from 20:00 h to wake up.

      An Actigraph will monitor their sleep during the week of the experiment. The subject will be
      invited to attend the Sleep Institute at 21:00 h. The subject will be asked to enter the test
      room, which will be dark, and sit in front of a computer screen for two hours at a distance
      of about 60 cm from the screen and perform the on-screen tasks between the hours of 21:00 and
      23:00 h. The tasks will include: reading and writing Microsoft Word documents, , and
      answering questions dealing with a document read and, solving verbal and arithmetic problems,
      while attempting to accomplish the task correctly and in the quickest time possible. The
      subject will be told that the purpose of the study is to examine the effect of the content of
      the tasks on the quality of sleep. During exposure, the subject will be allowed to eat and
      drink, but do not go to the bathroom. At the end of two hours of exposure to screen light,
      the subject will be connected to the sleep test system by a skilled technician. Body
      temperature and 6-hydroxymelatonin sulfate(6-SMT) in the urine will be measured using the
      on-set and off-set methods three times, at 21:00, 23:00 h, and close to the falling asleep
      time. Three measurements will be taken after awakening. After the sleep test system is
      installed, the subject will be asked to go to sleep and in the morning will be woken at
      his/her average waking time. After the examinee has been woken and has provided a urine
      sample and body temperature measurement, the sleep test system will be removed and the
      examinees will be given 30 minutes to organize him/herself, before performing the following
      tasks to assess his/her degree of fatigue and sleepiness: Continous Performance Test
      (CPT-III), the Brief Symptoms Inevntory (BSI) emotional questionnaire, and the Epworth
      Sleepiness Scale (ESS) and Karolinska Sleepiness Scale (KSS) questionnaire.
    

Intervention name(s): No intervention- base line; Acute; Chronic
Intervention type(s): Other; Other; Other
Intervention description(s): the subject will sited in a dim light room. No screen light illumination.; The subject will be sited in front of computer screen light illumination for 2 hours.; The subject will be sited in front of computer screen light illumination for 2 hours for 5 consecutive days.
Allocation: Non-Randomized
Intervention model: Single Group Assignment
Masking: Single (Participant)
Primary purpose: Basic Science
Keywords: screen illumination; melatonin; body temperature; cognitive functioning; light pollution