Home SEE WELL How Does Light Affect your Sleep?

How Does Light Affect your Sleep?

by Louise Wood
how does light affect your sleep

A good night’s sleep is just as important as regular exercise and a healthy diet.

Getting enough quality sleep helps support healthy brain function and mental and physical health.

The amount of sleep you get each day is important but it also needs to be good quality sleep. Signs of poor sleep quality include repeated wakeful periods during the night and feeling tired when you rise in the morning.

How much sleep do you need?

You will spend about one-third of your life asleep. This equates to about 8-9 hours a night for an adult. Teenagers need even more. Hormonal changes in the teenage brain shift them toward an owl-like body clock. They are not sleepy until later in the evening and then they struggle to wake up in time for school. With sleep deprivation, they are at risk of overeating, more likely to use nicotine and caffeine to stay awake, and more susceptible to mental disorders and suicide.

An easy way to see if you are getting enough sleep is to go without your alarm. Your body will wake naturally without an alarm if you have had a an adequate, well rested sleep. If you are relying on your alarm to wake you each morning you need to go to bed earlier.

Sleep deprivation

When you are asleep, your brain processes information. Our body clears toxins and repairs so it is ready for the next day. Adequate sleep promotes healing, immune function, regular metabolism, and much more.

Even with short-term sleep deprivation we begin to function below our potential. Stress hormones like adrenaline and cortisol increase in the blood and elevate blood pressure, affect metabolism and induce weight gain.

Research suggests even after staying awake for only 17-19 hours cognitive function declines. The cognitive decline is similar to being intoxicated by alcohol. The longer you stay awake, the worse the effects.

In 1963, a fit 17-year-old boy became part of his own science experiment. He stayed awake for 11 days and 25 minutes and was monitored by a sleep scientist. He exhibited serious cognitive and behavioral changes, paranoia, and hallucinations. For years following the experiment the teenager experienced insomnia.

Light and sleep: what’s the link?

Light is the most important external factor affecting your sleep. It is intuitive that sleep comes more easily when it is dark. But the link between light and sleep is quite complex. There are other external cues for sleep such as temperature, feeding times, and social interactions, but light remains the most important.

Your body has an internal clock that regulates when to be alert and when to be resting. This body clock is called your circadian rhythm and it controls your sleep and awake times through a 24-hour cycle.

Light plays a pivotal role in regulating your circadian rhythm by stimulating special light sensors in your retina in the back of your eye. These sensors detect the natural light and dark cycle over 24 hours and adjust the body’s circadian rhythm so the internal and external day coincide. When the retinal cells sense light, they produce melanopsin, a chemical that tells your brain to stay alert and awake. Melanopsin also suppresses melatonin which is a sleep-promoting hormone.

Melatonin is secreted when it’s dark outside. Night-time light exposure can confuse this process, suppressing melatonin production and keeping you up longer. Swapping your screen for a book an hour before bed, and making your room dark at bedtime will help you sleep more easily.

For people who have severe eye damage their sensors cannot detect light and they are unable to regulate their body clock.

With a more sedentary, often desk-bound lifestyle, you are deprived of natural light. We spend a lot of time inside and artificial light is not as bright as outdoors. Consequently, your sleep is affected. Artificial light is now a constant part of life. Office lighting, cell phones, tablet screens, computers, and more.

What about jet lag?

Jet lag affects people differently. If you suffer from jet lag it can really ruin your energy and enjoyment when you travel across time zones. Jet lag occurs when our circadian rhythm no longer aligns with the environment.

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Recent research into circadian rhythms has found a reliable method to reduce the symptoms of jet lag. Bright light exposure is the most effective way to cause a phase shift, an advance or delay in your circadian rhythm. This is best done for a number of days before you travel.

Light in the early morning makes you wake up earlier (phase advance) and light around bed time makes you wake up later (phase delay). After three days of light exposure in the morning the circadian rhythm shifted by an average of 2.1hours (phase advance).

When flying east, you need to phase-advance, so you use light exposure in the morning. When flying west you phase-delay by using light exposure at night before you travel. This helps the body adjust to the new time before you travel.

This form of “tricking” your circadian rhythm is also useful for night shift workers. They can reset their body clock by adding artificial light at the right time of the day to induce a phase shift.

Understanding your circadian rhythms will allow you to fly around the world without the effects of jet lag. 

10 tips to getting a good night’s sleep

  1. Minimize light exposure before you go to bed.
  2. Get as much morning light as possible.
  3. Stop using digital devices an hour or more before bed.
  4. Exercise regularly but not just before bed.
  5. Don’t consume caffeine (or alcohol) late in the day.
  6. Don’t nap during the day.
  7. Keep your room dark at bedtime.
  8. Keep your bedroom cool at 65°-68° Fahrenheit.
  9. Limit intermittent noise.
  10. Stick to the same sleep and wake times each day.

Sleep is a top priority for optimal health and well-being. It’s a good idea to tune into your circadian rhythm.

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