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March is National Sleep Awareness Month. It’s also the month during which days start to grow noticeably longer and the clock springs forward (at least in those places that still follow daylight saving time). That makes it the perfect time to discuss the effects of sunlight, and light in general, on our health and sleep.

1.    Morning Light Cues Us to Wakefulness to Begin the Day

Circadian rhythms, the 24-hour cycles of the body’s internal clock, promote sleepiness before bedtime, initiate sleep, and promote wakefulness before it’s time to wake up. These cycles of wake and sleep are affected by external cues, the sun being the strongest.  Sleep disorders medicine doctor Lawrence Kline recommends we  get bright light for 30-60 minutes every morning to promote that wakefulness. That light can come from taking a walk, sitting on the patio, or simply opening your curtains or blinds and sitting by the window while you have your breakfast or first cup of coffee.

Although sunlight has the strongest circadian effect, artificial light can signal the time for awakening and activity. Hence the slew of sunrise alarm clocks on the market. These clocks can be programmed to provide you with sunrise and sunset, as well as alarm sounds and other features. They begin with a low light that gradually brightens as you wake to avoid the jolt of light that might flash you back to your parents flipping on the light switch to wake you for school.

Light also has an effect on melatonin, a hormone produced in response to darkness that causes drowsiness as its levels rise. Exposure to light causes “the acute suppression of melatonin,”  which supports wakefulness.

2.    Morning Light Improves Our Sleep at Night

Natural daylight has been shown to not only advance the time of falling asleep but also to affect the duration of sleep and to improve sleep quality. As physical exercise, which can also improve sleep, is often intertwined with time spent in natural daylight, it’s not necessarily clear to what degree each might be responsible for improved sleep.

The opposite is true when we expose ourselves to light late in the day. Whereas blue light from the sun in the early part of the day can improve performance during the day and sleep at night, artificial blue light later in the day can interfere with our sleep. Such exposure was not a concern until recently with the advent of artificial lighting, which can turn night into day.  Excessive exposure to artificial light later in the day can upset our circadian rhythms, negatively affecting our sleep, and cause “other concerning health impacts including worsened metabolism, weight gain, cardiovascular problems, and perhaps even an elevated cancer risk.”

The light does not need to be bright to interfere with circadian rhythms and melatonin secretion. “A mere eight lux—a level of brightness exceeded by most table lamps and about twice that of a night light—has an effect.”  Blue light seems to have the most powerful negative effect. The most common sources of blue light include smart phones, televisions, and LED lights. That’s why it is recommended that these sources of blue light be turned off two to three hours before bedtime.

3.    Light Positively Affects Our Moods

Although the reason for the positive effect of light on mood is not thoroughly understood, “light can also be used as an effective and noninvasive therapeutic option with little to no side effects, to improve sleep, mood and general well-being.”

Bright light therapy (BLT) was introduced for the treatment of Seasonal Affective Disorder in 1984. An article on the National Institute of Health’s website reviewing the effects of light on circadian rhythms, sleep, and mood noted that BLT is a “first-line treatment for SAD” and a “second-line treatment for non-seasonal depression.” It can be delivered by commercially available therapy lamps, “but natural daylight during a regular one-hour morning walk has been shown to be similarly effective.”

4.    Light Hastens Our Recovery from Jet Lag

A common application of light is to treat circadian rhythm sleep-wake disorders (CRSWD), including jet lag. Generally, jet lag happens when we cross three or more time zones, and our bodies’ internal clocks are at odds with the time of day at our destinations. Symptoms of jet lag include fatigue, insomnia, irritability, and stomach problems and can take 1-1 ½ days per time zone crossed to alleviate.

Acclimating to the new time zone is not as simple as staying awake until it’s bedtime at your destination. Just “following the day-night cycle in the new time zone” won’t resolve jet lag. Instead, it could make it worse. You’ll need to time periods of daylight and darkness to sync your circadian rhythm with local time. You’ll want to expose yourself to morning light if you need to adjust to an earlier time zone when you travel east and get more light in the evening to stay up when you travel west. If natural light is not available, exposure to artificial light can be used to reset your circadian clock.

5.    Elimination of Light in Bedrooms Lets Us Sleep

Light has many beneficial effects but not when it’s time to sleep. As closing your eyelids is not enough to block all the light, there are a few things you can do to eliminate light and improve your sleep. Avoid using electronics before bedtime as they stimulate your mind, delay bedtime, and “can disrupt circadian timing, melatonin production, and overall sleep.” If you can’t entirely avoid them, place them in night or dark mode.

Dim or turn off lights as you are near bedtime. This is a perfect time for candlelight, although we don’t recommend falling asleep with candles lit. Eyelids can’t block light completely so circadian rhythms can be affected by light through closed eyes.  Studies have found that having lights on while you sleep, including lights from the television or other electronics, can affect the “circadian regulation of metabolism, increasing the risk of weight gain even if sleep itself is not disrupted.”

If you cannot eliminate all the light in your bedroom, consider adding an eye mask to your bedtime routine. If you are concerned with safety when getting up at night, consider motion-activated night lights to guide you to the bathroom.

We are looking forward to the longer days and nights of great sleep.

-The Customer Care Team

Read more:

5 Reasons to Make Eye Masks Part of Your Bedtime Routine

Bedtime Rituals for Better Sleep


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