Michael Hunter, MD on Medika Life

Is Your Bedroom Dark Enough?

ARE YOU EXPOSED TO AMBIENT LIGHT WHILE YOU SLEEP? You may be harming your health. It may be time to ditch the nightlight and invest in blackout shades. And if you leave the television on in your bedroom as you fall asleep, please stop.

Many of us struggle to get the optimal nightly seven to nine hours of sleep. The American Academy of Sleep Medicine and Sleep Research Society recommends that adults (ages 18 to 60) sleep seven or more hours regularly for optimal sleep health.

The National Sleep Foundation consensus report recommends seven to nine hours for adults aged 18 to 64 and seven to eight hours for those 65 and older.

Getting insufficient sleep puts your physical and mental health at risk. According to the US Centers for Disease Control (CDC), more than one-third of adults in the United States report sleeping fewer than six hours daily. The rates are even higher among younger adults and those with a low socioeconomic status.

Short sleep can increase our risks of cardiovascular disease, obesity, and premature mortality. Poor sleep takes a toll on the mind and the body.

Sleep, ambient light, and cardiovascular risk

Sleep researchers at Northwestern University (USA) report that exposure to even small amounts of ambient light at night can negatively affect cardiovascular function.

We already have some evidence that too much evening light may negatively impact our metabolism. Light exposure is associated with a drop in glucose (sugar) tolerance and decreased insulin resistance.

Light exposure before bedtime has perils.

Insulin resistance occurs when cells in your muscles, fat, and liver don’t respond well to insulin and cannot use blood glucose for energy. To make up for this change, your pancreas makes more insulin. With time, your blood sugar levels rise.

Expose yourself to pre-bedtime light, and you may put your sleep and some physiological functions at risk.

Photo by Fran Jacquier on Unsplash

Light exposure during bedtime also is dangerous.

Does that muted television threaten you and your sleep? According to a new study of healthy young adults, the answer appears to be yes.

Researchers examined heart rate, sleep quality, glucose levels, and other variables during one night of sleeping in a dark room (three lux) and one night in a moderately lit room (100 lux).

Here are the findings:

Sleeping in a moderately lit room increased heart rate and activated the sympathetic nervous system during sleep. The practice also impaired the next morning’s glucose regulation.

Sleep specialist Dr. Nilong Nyas explains:

“Your eyes are your direct connection to the part of the brain that controls the circadian rhythm. [Light exposure] is interpreted by the brain to allow the chemical reactions to take place for healthy (or unhealthy) sleep cycles.”

Dr. Nyas adds that “if there’s a significant amount of light interference at a time when your body’s trying to sleep, it can cause poor sleep or unhealthily programmed sleep cycles, which can lead to a significant number of other medical issues.”

For me, the research findings mean sleeping in as dark a room as possible to optimize my sleep quality and health.

Photo by bruce mars on Unsplash

Sleep struggles? Try these strategies.

Here are some ways you may be able to improve your sleep, courtesy of the Sleep Foundation:

  • Cover your windows. Consider investing in blackout curtains if your blinds or curtains don’t sufficiently block light.
  • Mind the gap. Turn off any hallway lights before bedtime, or place a rolled-up towel against the door gap to stop light from entering.
  • Wear an eye mask. Light can penetrate our eyelids, potentially inhibiting the sleep hormone melatonin.
  • Ditch the electronics. Put away light sources such as computers, cell phones, charging stations, digital clocks, and other electronics. Cover their lights or put them outside your bedroom.
  • Dim the lights. In the hours pre-bedtime, try transitioning to dim ambient light.
  • Consider your nighttime needs. I sometimes need to use the bathroom in the middle of the night. I try to avoid exposure to high-volume light. Still, be safe: You may need motion-sensor nightlights, but try to minimize your light exposure if it is safe to do so.

Other strategies include:

  • Avoiding alcohol.
  • Cutting off caffeine early in the day.
  • Avoiding vigorous exercise in the late evening.

In summary, light exposure during sleep impairs cardiometabolic function. Are you prioritizing high-quality sleep of adequate duration?


Medika Life has provided this material for your information. It is not intended to substitute for the medical expertise and advice of your health care provider(s). We encourage you to discuss any decisions about treatment or care with your health care provider. The mention of any product, service, or therapy is not an endorsement by Medika Life

Michael Hunter, MD
Michael Hunter, MD
I received an undergraduate degree from Harvard, a medical degree from Yale, and trained in radiation oncology at the University of Pennsylvania. I practice radiation oncology in the Seattle area.

Michael Hunter, MD

I received an undergraduate degree from Harvard, a medical degree from Yale, and trained in radiation oncology at the University of Pennsylvania. I practice radiation oncology in the Seattle area.

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