Effect of Lights on Sleep Quality

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Light affects sleep quality because it influences the circadian rhythm. The circadian rhythm is a series of physiological changes that follow a 24-hour internal clock. The circadian rhythm responds most to light and darkness cues.

Light tells the body it is time to be awake, and darkness tells the body it is time for sleep. The definition of light includes natural and artificial light. Natural light is daylight from the sun, and artificial light includes lamps and screen devices such as laptops and cell phones.

Light can harm sleep quality in two ways. The first way is that light reduces the melatonin levels in the body. Melatonin is a hormone that promotes sleepiness, and it is released in higher amounts at night as part of the circadian rhythm process. Exposure to light causes the body to decrease its melatonin amount, leaving the individual more awake than tired.

The second way light harms sleep is that it hinders sleep cycle transitions. People experience multiple sleep cycles during the night. The first two stages of a sleep cycle are a lighter sleep. Most people should stay asleep as they transition between cycles, but light exposure can make it more likely that you wake up between cycles, leading to fragmented rest.

Tips to improve sleep quality include using blackout curtains or eye masks, keeping a consistent sleep schedule, and cutting off the use of electronics before bed. Blackout curtains and eye masks can block out light. Maintaining a consistent sleep schedule will help set your circadian rhythm for better rest. Cutting off your use of electronic screen devices before bed will curb the effects of blue light exposure.

How Does Light Affect Sleep?

Light affects sleep because it influences the circadian rhythm. Circadian rhythms are physiological changes that follow a 24-hour biological clock, and light is the primary influence over circadian rhythms.

Light signals that it is time to wake up, while darkness signals that it’s time to rest. The types of light that influence circadian rhythms include natural daylight and artificial light from lamps and electronics screen devices like laptops and cell phones.

Light affects sleep in two ways. The first way is that light can impair transitions between sleep cycles. People move through multiple sleep cycles while at rest. There are four stages in a cycle, and the first two stages are a lighter sleep. Most people should stay asleep at the top of a new cycle, but light exposure increases the odds that you’ll wake up, causing more disturbed rest.

The second way light affects sleep is by influencing the production of melatonin, a sleep-promoting hormone. The circadian rhythm increases and decreases melatonin amounts based on light exposure.

Melatonin amounts drop when there’s light present and increase when it’s dark. If you expose yourself to excess light at night, this could delay sleep onset. The reason for this is that your body won’t release as much melatonin, causing you to feel more awake.

What is the Effect of Light on Circadian Rhythms?

Light has a significant effect on circadian rhythms because light is their biggest influence. A circadian rhythm is a series of physiological changes based on the body’s biological 24-hour clock.

The circadian rhythm prepares the body for rest or wakefulness according to light exposure. For example, darkness prompts the body to increase melatonin production, and light reduces it. Melatonin is a hormone that fosters tiredness. You are likely to feel tired with more melatonin in your system than with less.

What Kind of Circadian Rhythm Disorders can Occur because of Light?

Light can cause different kinds of circadian rhythm disorders such as Jet Lag and Shift Work Disorder. Circadian rhythm sleep disorders are disruptions to an individual’s sleep-wake schedule.

Symptoms of circadian rhythm disorders include trouble falling asleep, difficulty staying asleep, and waking up too early. Light is an environmental factor that causes circadian rhythm disorders by interrupting sleep patterns.

Illustration of a Female Doctor at Work and in Bed
1. Shift Work Disorder

Shift work disorder is a circadian rhythm disorder caused by changing work schedules or overnight work. The work schedule often does not align with the body’s natural rhythm or makes it hard to maintain a consistent sleep schedule.

When it’s dark out, this tells the body it is time for sleep, but those who work at night are going against light’s influence on the body.

The harms of shift work include frequent tiredness, discomfort, negative moods, gastrointestinal problems, and decreased sex drive. People with Shift Work Disorder are at a higher risk for alcohol and substance abuse, weight gain, hypertension, heart disease, and breast and endometrial cancer.

2. Jet Lag

Jet Lag is a circadian rhythm disorder caused by quickly changing time zones after plane travel. Travel can interfere with your usual sleep-wake schedule and make it difficult to adapt to your destination. Light can influence jet lag because if it is light out at one location when you take off and dark at the other – or vice-versa – this could hinder your sleep-wake schedule at your destination.

The harms of jet lag include appetite changes, changes to stomach and bowel functions, fatigue, discomfort, and negative moods. Frequent international travelers are at an increased risk for Jet Lag.

Illustration of a Guests Resting on a Bed

What is the Effect of Light on Melatonin Hormone while Sleeping?

Light’s effect on the melatonin hormone is that it influences the amount of melatonin in the body. Sleep and melatonin are linked because melatonin is a sleep-promoting hormone.

When it’s dark out, the body releases extra melatonin to help prepare you for rest, and when there’s light around, the body cuts back on melatonin, so you feel more alert. Exposure to light at night can trick the body into stopping the release of additional melatonin, leaving you more alert and delaying sleep onset. The benefit of melatonin is that it fosters tiredness, and a melatonin deficiency will cause alertness.

What is the Effect of Light on Stages of Sleep?

Light’s effect on the stages of sleep is that it can weaken transitions between sleep cycles. People move through multiple sleep cycles when they are sleeping. There are four stages of sleep in a cycle.

It is important to complete each stage for optimal emotional, physical, and cognitive health. The first two sleep cycle stages are a lighter sleep cycle. Most people should remain asleep when they transition to a new cycle, but light exposure increases your risk of waking up between cycles. If you frequently wake up during the night, you are less likely to feel well-rested in the morning.

What Types of Light Affect Sleep?

The types of light that affect sleep include sunlight, lamps, and electronic screen devices such as cell phones. Sunlight is the primary trigger for the body’s natural sleep-wake rhythm, so people are naturally inclined to be awake during the day and asleep at night. Lamps are typically used at night to light up a space or room.

Lamps can affect sleep by suppressing melatonin production and causing an individual to wake up from sleep. Electronic screen devices emit a blue light that delays melatonin production and causes alertness. Devices that produce blue light include LED lights, smartphones, TVs, computers, tablets, and video games.

Illustration of a Lady on an Adjustable Bed Working on Her Laptop

What Colors of Light are Harmful for Sleep?

The colors of light harmful for sleep are blue and white. White light is colorless that contains all the shades of the color spectrum. Daylight is an example of white light. Exposure to white light can be good during the day for improving your mood and energy, but white light can hinder your ability to doze off if you are trying to sleep.

Blue light is a type of light emitted from electronic screen devices like cell phones and televisions. Harvard researchers found that blue light suppressed melatonin production and adjusted the circadian rhythm twice as much as green light.

How Much does Light affect Sleep?

Light significantly affects sleep because it impacts the circadian rhythm, melatonin production, and sleep cycles. The circadian rhythm is a series of physiological responses that follow a 24-hour internal clock, and they mainly respond to light and darkness.

Light promotes wakefulness, while darkness promotes sleep. Exposure to light at the wrong times can throw off the internal clock and make it harder to sleep well.

Light can harm sleep quality in two ways. The first way light harms sleep is that it decreases the amount of melatonin in the body. Melatonin is a natural hormone that is designed to support tiredness.

Normally the body releases extra melatonin at night as part of the circadian rhythm. When exposed to light at night, the body will instinctively cut back on melatonin production, causing the person to feel more alert instead of tired.

The second way light harms sleep is by obstructing sleep cycle transitions. People move through sleep cycles while at rest. There are four stages in a cycle, and the first two stages at the top of the cycle are a lighter sleep. Light exposure increases the risk of waking up between cycles when you move into that lighter sleep, worsening sleep quality.

Research from the Defense Meteorological Satellite Program found that light exposure reduced sleep duration and increased the risk of daytime fatigue, waking up disoriented, and impaired cognitive abilities.

Should you Sleep in Pitch Darkness?

Yes, you should sleep in pitch darkness. Pitch darkness means that there’s a complete absence of light around you. No light must be peeking through since even a little exposure can affect the body’s ability to doze off. The benefits of sleeping in pitch darkness are that it will encourage sleepiness and prevent distractions that could wake you.

There are several ways to help create more darkness to support better sleep quality. The first way is to use blackout curtains or an eye mask. These products will physically block out light. The second way is to cut off your electronic screen time at least an hour before bed. Furthermore, keeping electronic devices out of your bedroom or putting them on a ‘do not disturb’ setting can prevent notifications from distracting you during the night.

Does Sunlight Disrupt your Sleep?

Yes, sunlight disrupts your sleep. Sunlight directs the body that it is time to be awake, making it harder for you to sleep. Sunlight is harmful to those who need to sleep during the day, such as shift workers. Sunlight exposure is beneficial for setting your circadian rhythm, boosting your mood, and improving energy levels.

Illustration of a Woman Waking Up
What are the Health Effects of Naps in Sunlight?

Naps are shorter periods of sleep that occur during the day. Napping is normal for babies and small children, but some adults may take them to catch up on rest if they are tired. The health benefits of napping in sunlight are not positive. Experts say you should nap in a dark space, and sunlight can make it harder to nap because you won’t feel as tired.

Why do some people prefer to sleep with the Lights on?

Some people prefer to sleep with the lights on because it provides comfort. For example, some children may be scared of the dark and want a nightlight for their bedroom, or some adults who live alone may find the light from their television comforting. Experts say red light is better if you need to sleep with a light on because it doesn’t impact the circadian rhythm.

How to Adjust your Bedroom Environment and Lights to Get the Best Sleep

The following tips will show you how to adjust your bedroom environment and lights to get the best sleep.

  • Put up blackout curtains: Blackout curtains are designed to prevent outside light from entering your bedroom, which should translate to more restful slumber.
  • Wear an eye mask: Eye masks are an economical option for those who don’t want to invest in blackout curtains. These masks are designed to keep out distractive light.
  • Use red light: Red light is helpful for those who prefer to sleep with some sort of light on because it does not interfere with the circadian rhythm. 
  • Avoid electronics before bed: Avoiding your screen devices an hour before bed is helpful because it prevents melatonin suppression, which should foster tiredness for better quality sleep.
  • Put devices on ‘do not disturb’: Putting your cell phone and tablet on ‘do not disturb’ mode helps ensure that any overnight sound or light notification won’t wake you up.

How Important is it to Adjust the Mattress Position according to the Light for Quality Sleep?

It is important to adjust the mattress positions according to the light for quality sleep because if your mattress is more exposed to light, it could be harder to rest well.

The best place to put your bed for quality sleep is away from the window because sunlight or ambient from the city may interfere with your rest. Facing away from the window should also help since your eye line is not directly facing any lights.

Content Writer

Jill Zwarensteyn is a content writer for Sleep Advisor and is enthusiastic about providing helpful and engaging information on all things sleep and wellness.

Based in Los Angeles, she is an experienced writer and journalist who enjoys spending her free time at the beach, hiking, reading, or exploring new places around town.

She’s also an avid traveler who has a personal goal of being able to successfully sleep on an airplane someday.

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