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Study warns: health risk caused by sleeping in light even dim!

Some people find that they cannot sleep if there is even a dim light flash in their bedroom. Now, new research published in the scientific journal PNAS has found a strong health argument for sleeping in the dark.   Sleep researchers at Northwestern University's Feinberg School of Medicine found that exposure to even a small amount of ambient light during the night could harm cardiovascular function during sleep and increase insulin resistance the next morning.    The authors of the study recognize current and emerging scientific evidence that excessive exposure to light in the evening may negatively affect metabolic functions, i.e. low tolerance of glucose (blood sugar) and low insulin resistance.




Some people find that they cannot sleep if there is even a dim light flash in their bedroom. Now, new research published in the scientific journal PNAS has found a strong health argument for sleeping in the dark.


Sleep researchers at Northwestern University's Feinberg School of Medicine found that exposure to even a small amount of ambient light during the night could harm cardiovascular function during sleep and increase insulin resistance the next morning.


The authors of the study recognize current and emerging scientific evidence that excessive exposure to light in the evening may negatively affect metabolic functions, i.e. low tolerance of glucose (blood sugar) and low insulin resistance.


Simply put, exposure to light before bedtime may be harmful to sleep and some physiological functions.


  • Your brain uses the presence of light as a signal that it's time to wake up and alert, and darkness as a sign that it's time to sleep.
  • Exposure to light activates the sympathetic nervous system (SNS) and increases heart rate so you are ready to enjoy the day.
  • On the other hand, at night, the parasympathetic nervous system (PNS) - the rest and digestion system - should take the lead
  • which promotes relaxation, reduces heart rate, and maintains healthy metabolism.


As the sun sets and darkens, the brain produces the sleep hormone melatonin, which is responsible for informing your system that it's time to relax and sleep.


Therefore, exposure to night light (from bedside lamps to TV screens) is thought to inhibit melatonin production and disrupt the healthy and normal pattern of sleep.


  1. Neelong Vyas, a certified pediatrician and sleep consultant at Sleepless in NOLA
  2. and a medical review expert at SleepFoundation.org (who was not involved in the study)
  3. explained that "your eyes are your direct contact with the part of the brain that controls the circadian rhythm.


Exposure to light by the brain is explained to allow chemical reactions to occur for healthy (or unhealthy) sleep cycles. " If there is a great deal of photosynthesis at the time your body tries to sleep, this may cause poor sleep or unhealthy sleep cycles, which may lead to a large number of other medical problems. "


Researchers took a group of healthy young people and adults and compared data such as their sleep quality, heart rate and glucose levels during one night of sleep in a very dark room, and during one night of sleep in a moderate-light room.


The results found that sleeping in a moderately lit room can increase heart rate and activate the friendly nervous system during sleep, as well as impair your ability to regulate glucose the next morning.


The study concluded that "attention to avoiding exposure to light at night during sleep may be beneficial for cardiovascular health."


Dr. Vyas added:

  1. "Progressively reducing light from your sleep environment and eventually eliminating it will allow for improved sleep."
  2. There are simple ways to dim your bedroom to ensure a quiet and healthy night's sleep.


The Sleep Foundation explains


"Light from the sun and moon, as well as security lights or street lights, can enter the bedroom through windows."


According to the organization, if blinds do not adequately obscure outside light, you may consider investing in blinds. Covering the window with aluminum foil is a low-cost alternative that also prevents external light. "