Ask a Doctor: Will getting out in the sun help me sleep better?


Q: I have trouble sleeping. I spend my day in an indoor office and often come home when it’s already dark. Would getting out more help me sleep?

A: Being outdoors for at least some parts of the day can help you sleep better. Get sunlight early, walk outside in the afternoon, reduce blue light at least three hours before bedtime and go to bed in darkness to improve your sleep.

Light affects melatonin, a hormone that helps regulate sleep. It does so even in some blind people with no conscious perception of light.

Researchers soon discovered why: Our retinas contain specialized cells that are uniquely sensitive to light of wavelengths around 460 nanometers, or blue light.

As day breaks, blue light from the rising sun triggers those retinal cells to signal our brains to halt the production of melatonin. Later, as our environment becomes darker and blue light is replaced by the warm hues of the setting sun, melatonin ramps up again, allowing us to sleep.

Scientists hypothesize that blue is significant because cells in the retina that perceive light evolved first among dwellers of oceans, where the blue wavelengths penetrate the water’s surface more easily.

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Blue light and circadian rhythms

The human eye evolved according to these natural light conditions, but electric lighting – incandescent bulbs were patented by Thomas Edison in 1880 – disrupted our circadian cycles. Modern societies began to stay up later, work longer hours indoors and sleep in one continuous overnight stretch instead of two shifts, known as biphasic sleep (that was once a thing).

We are now exposed incessantly to blue light in the evening, from the fluorescent lights of our homes and offices, the streetlights and headlights that guide our way through rush hour, and the screens and smartphones we stare at as we lie in bed.

It’s taken a toll on our slumber. A study of nearly 20,000 American adults found that those who live in areas with more outdoor nighttime lights – such as streetlights – had a delayed bedtime, shorter sleep duration and increased daytime sleepiness.

Skyscraper construction in cities has created “urban canyons” that rob us of natural light – with a major impact on our health, said Karolina Zielinska-Dabkowska, a lighting designer and assistant professor in architecture at Gdansk University of Technology in Poland.

Besides disrupting sleep, artificial light exposure at night is linked to breast and colorectal cancer, Zielinska-Dabkowska said in an email interview. “It’s also a risk factor for cardiovascular disease, Type 2 diabetes, hypertension, obesity and depression,” she said.

There are a few ways we can win back some control of our circadian rhythms.

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Get morning light

“Exposure to daylight in the morning will have a positive impact on your quality of sleep at night,” Zielinska-Dabkowska said.

Your circadian rhythm is highly sensitive to light in the first hour after waking. Get some blue-rich sunlight early in your day, she advised, ideally without wearing sunglasses or contact lenses to best activate your biological clock.

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Trade the afternoon latte for a walk outdoors

The body produces melatonin again after lunch. Some cultures accept the sleepiness produced by melatonin and encourage siestas. Other cultures face it with tea, coffee or the Bostonian urge to descend upon the nearest Dunkin’ at 3 p.m.

Sunlight, however, can stop melatonin from telling you to snooze. A study among college students showed that exposure to even artificial blue light in the early afternoon not only improved post-lunch sleepiness but also boosted memory.

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Rethink your home lighting

Move your desk to a space that gets the most natural light during the day.

Dim all lights at least three hours before bedtime.

The lighting should be subdued and depleted of blues. On July 31, the United States will stop producing incandescent bulbs (known for their warmer sunset-like spectrum), so unless you hoard them, swap out your fluorescent lights for amber LED bulbs, or better yet, smart bulbs. These can be programmed to be bluer during the day and redder in the evening (aim for 2,700 Kelvin or below).

“Also the placement of light sources is important,” Zielinska-Dabkowska said. Avoid overhead lighting, and place lamps low to the ground or on tables, with shades to avoid looking directly into the source, she recommended.

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Change your phone’s settings

Avoid screen time before you sleep, but because that can’t always happen, turn on the “night shift” setting on your iPhone or “blue light filter” on an Android phone to adjust the color of your screen in the evenings.

“These features do not completely reduce the blue wavelengths,” Zielinska-Dabkowska cautioned, but they “mitigate some of the impact of such devices.”

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Sleep in darkness

Experts recommend a room being no brighter than 1 lux during sleep – the equivalent of a candle a little over three feet from the eye. If you get a lot of light pollution from outside your house, experiment with a sleep mask or blackout curtains.

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What I want my patients to know

Taking small doses of melatonin is generally safe in the short term, but a disturbingly high percentage of melatonin supplements don’t contain what’s on the label. Before trying a pill, talk to your doctor about cognitive behavioral therapy if you have insomnia – it’s our first-line recommendation because it can address the underlying cause of your inability to sleep as opposed to medicines that target symptoms.

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Dr. Trisha Pasricha. PHOTO:

Trisha S. Pasricha is a physician at Massachusetts General Hospital, an instructor in medicine at Harvard Medical School and a medical journalist.




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