How to Create A Great Sleep Environment According to Science

Let’s face it, it’s pretty easy to take your bedroom for granted. Especially with everything going on right now, I bet a lot of people are falling into bed at the end of some very long days, worrying about life and the future, hoping that sleep will come quickly and last long enough to keep from feeling exhausted the next day.

Even in much easier times than these, it’s easy enough to lose sight of the importance of maintaining an optimal sleep environment. But it matters. A lot. Plenty of sleep problems arise directly out of our sleeping spaces, whether that’s from noise, or light, or temperature issues.

You’ve probably heard the advice to keep your bedroom like a cave: cool, dark, quiet. All good advice. But there’s more to it than that.

I wrote a while back about the fundamentals of creating an optimal bedroom environment. But we haven’t touched on the topic for a while. And there’s some recent research that gives new and actionable insights into just what works best for most people in a sleep space, when it come to light, sound, texture, noise and temperature.

Since we’re all spending so much time at home right now, it seems like a good time to take a fresh look at our sleeping spaces, and put into action what the latest science reveals about what makes the most sleep-friendly bedroom.

What is the best bedroom temperature?   

Without a doubt, this is the most common question I get from people about their sleeping spaces. The ideal temperature varies by individual, and a lot of this does depend on individual preference and tolerance for heat and humidity, as well as individual health factors, including body weight, hormone imbalances, the stages of menopause, and conditions such as obstructive sleep apnea and GERD. Here’s a thorough rundown of how the body manages temperature during sleep, and the many factors to consider in maintaining ideal temperature for your night’s sleep.

That said, there is a range that likely captures nearly everyone’s optimal temperature—and there’s some new research that shows that range, as well as potentially ideal single temperatures within it.

I find people often tend to think about air temperature as a stand-alone factor in our bedroom environments. But temperature interacts with other factors in critical ways that affect how we experience the heat or coolness of our sleeping spaces.

Scientists at San Jose State Research Foundation and NASA Ames Research foundation did a review of scientific research about what creates the optimal sleep environment. They found the ideal temperature range to be very broad—between 17-28 degrees Celsius, which is 62-82 degrees Fahrenheit.

But they also found that other temperature-related factors heavily influenced the optimal temperature within that range. One of those factors is humidity. I know we all complain a lot about the humidity in general—but I’m not sure people pay enough attention to humidity in their sleep environments. In their analysis, scientists found that the optimal range for sleep is 40-60% relative humidity. Depending on where you live, what time of year it is, that can mean you need to add or subtract humidity from your bedroom to sleep at your best.

The other factor was the “bedding microclimate.” That’s right, your bed has its own climate! It’s affected by what you wear to bed, by your mattress and pillows, by your bedding itself—sheets and covers and all. These days, you’re not only able to influence your bed climate by the types of materials you use in your bedding (more scientific information on that in just a minute). You also can tightly control your bed climate with mattress pads that will keep your bed’s microclimate at an optimal temperature.  

THE TAKEAWAY? Think about bedroom temperature—but don’t ONLY think about bedroom temperature. Take humidity and your bed climate into consideration, as well as skin temperature and air flow (more on those in a minute) and look at optimal sleep environment temperature as an interplay among these factors.

For a long time, I have recommended to my patients the Chilipad, a mattress pad that allows you to regulate the temperature within your bed. You can customize the temperature on your side of the bed, and your partner can do the same on their side, so each of you gets to sleep in the microclimate that’s exactly right for them.

Some other recent research looked at the impact of bedding climate on sleep, and specifically at the distribution of heat and the sensations of temperature across the body within bed. This study found the bed temperature around the body’s core is the best measurement for determining a comfortable, optimal sleep temperature. This research also found that when we sleep, we tend to experience a broader range of comfortable temperature sensations on our face, compared to the rest of our body. 

THE TAKEAWAY? Your face can feel cool while your body feels warmer, and you’ll sleep well. You can keep your room on the cool side, and regulate temperature within your bed itself. Just don’t go too far in turning the heat down when it’s cold—a really cold bedroom will interfere with your sleep.

Keeping your head cool doesn’t just feel comfortable for sleeping—it can actually help you slow down the racing thoughts that interfere with your sleep. Surprised? Research has shown that cooling the forehead slows down activity in the frontal cortex, and helps people fall asleep faster, sleep more deeply, and sleep longer. High levels of activity in the frontal cortex are common in people who can’t sleep. This is the area of the brain where ruminating thoughts take place. My patients who have trouble calming their minds at night have had great success with EBB, a forehead cooling band worn at night. EBB cools the forehead to the optimal temperature range—15-18 degrees Celsius, as determined by scientific research. This cooling of the forehead reduces the metabolic activity of the frontal cortex, and quiets the mind so you can sleep.

Here’s one other piece of recent research I want to highlight on temperature. A study in China included both a large-scale survey and a field study about the effects of environment on sleep, capturing both objective measurements and the subjective impressions of sleepers about how their sleep quality was impacted by their environment. There are a few key takeaways here. The optimal sleep environment temperature was determined to be 24.2 degrees Celsius, or about 75 degrees Fahrenheit. Measurements taken in a field study showed a strong relationship between a person’s satisfaction with their sleep environment and their sleep quality. In other words, paying attention and care to your bedroom really does matter. And there are gender differences to explore in relation to sleep environments. Men in this study had lower sleep quality than women. (More on some other gender differences in just a minute.)

Some quilts will keep you warmer—and give you more restful sleep—than others

You might not have given much thought to the materials used in your quilt or bedspread. A lot of people think mostly in terms of light and heavy, for warm and cold sleeping weather. I’ve written before about how the materials in our bedding and sleep clothing—as well as our mattresses and pillows—can affect comfort in bed and the ability to sleep well.

Recent research zeroed in for a close look at how three different types of quilt materials performed in un-heated bedrooms, analyzing how each type affected sleep and sleepers’ thermal comfort. Scientists investigated the performance of quilts made of goose down, duck down, and cotton. They took objective measurements of skin temperature and bed climate, and collected subjective data about how sleepers perceived their sleep under each type of quilt.

Both subjective and objective data showed that the material of the quilt used had a significant impact on sleep quality and on sleep comfort. Of the three, the goose down quilt performed the best. EEG measurements showed that sleepers using goose down had longer periods of slow-wave sleep, the deep sleep stage in which the body does some of its most critical work to restore and repair cells and boost the immune system. Sleepers using goose down quilts also had higher skin temperatures and warmer bed climates. The cotton quilt was the least optimal for sleep, according to this research. 

THE TAKEAWAY? For cold climates and winter months, it’s worth the investment in a down quilt. If you’re not able to tolerate down, consider hypoallergenic alternatives.

Your bedroom needs to be quieter than you think

How loud does noise need to be to disturb your sleep? All of us are different, of course. And different sounds create different responses. Someone who can sleep through a thunderstorm will jolt awake at the sound of their child crying in the next room. The researchers at NASA and San Jose State, in their optimal bedroom environment analysis, found that threshold level for bedroom noise is 35dB. That means, to maintain an optimal sleep space, all noise needs to be at a decibel level below 35. What does 35 dB sound like? Here are some decibel level comparisons for perspective:

An airplane taking off is 150 dB

Thunder? About 120 dB

A lawn mower is around 100 dB

A bird call is roughly 40dB

Regular conversation between people sitting at a dinner table? 60 dB

A whisper? That’s about 20 dB

Your own breathing—and your partner’s, if they don’t snore, is about 10 dB. So, 35 dB is not quite 2x as loud as whispering, and definitely quieter than normal conversation. That’s pretty quiet, definitely a lot quieter than the TV volume that so many of us fall asleep to. We’re most likely to awaken from sound that’s 50 dB or less when we’re in the lighter stages of 1 and 2 sleep; deeper sleep awakenings typically require louder noises.

I’ve written before about the different types of noise that interfere with sleep, everything from snoring, to fireworks to TV and electronics to environmental noise. Each form of noise takes different remedies to address. All of them are worth addressing. (That noise article of mine is a good roundup of suggestions for an array of disruptive sounds.) White noise machines are a great sleep tool for masking unwanted noise, reducing awakenings, and increasing sleep amounts.

THE TAKEAWAY? Total silence is not necessarily the solution, but an optimal bedroom is quiet. My patients have had success with sound machines, and I especially like the iHome Zenergy sleep system for introducing quiet sounds into the bedroom, to promote relaxation and help block other, more disruptive noises. Melatonin has also been shown to improve sleep quality against the effects of noise. In research, melatonin did a better job of protecting sleep quality in a noisy environment than earplugs. Earplugs can be useful, but people sometimes find them uncomfortable. And usingearplugs too frequently can lead to earwax buildup. When you do use earplugs, be sure they are clean (or new, if you’re using the disposable kind) with each and every use, to avoid exposing the ear canal to dirt and bacteria. If you suffer from tinnitus, I recommend avoiding using earplugs. Here’s how tinnitus can affect sleep.

I love using earplugs for travel, but wouldn’t opt to use them at home every night. I’d rather see people use a white noise machine or sound machine to mask the noises you can’t control, and also address the underlying causes of noise-related sleep problems, whether that’s partners’ snoring, or a TV that runs late into the night without a shut-off timer.

For men and women, the ‘optimal’ sleep environment is different

A couple of these recent studies shed light on the differences in how men and women experience their sleep environments. A 2019 study looked specifically at gender differences in relation to temperature, and use of thermoelectric cooling technology—that’s the tech that’s found in the Chilipad I mentioned above. This study found women preferred a warmer sleep environment than men, requiring less powerful thermoelectric cooling to achieve optimal sleep in warm temperatures. (That’s why it’s so cool and important that Chilipad let’s couples set their own individual cooling level within the same bed.)

And in the study of optimal bedding materials, scientists found some interesting differences in skin temperature for men and women during sleep. Women’s average skin temperature was higher than men’s, but their foot temperature was lower than men’s. That suggests women need to pay some extra attention to their feet (and their hands) during cold-weather sleeping. 

There are key differences in the ways men and women sleep. Men and women’s circadian clocks run differently. Men’s tend to run later and a little longer, which means women are apt to have a preference for waking earlier and going to bed earlier, across different chronotypes. Women, on average, spend more time in slow wave sleep, which may explain why science has shown that women tend to perform better when sleep deprived and to rebound more quickly from short-term sleep loss. Women and men also experience different, gender-specific sleep challenges at different points throughout adulthood, including the impact of menopause. I’ve written extensively about menopause and sleep, and also about sleep throughout the decades of our lives.

THE TAKEAWAY? Don’t assume a one-size fits all approach is going to get both you and your partner the best sleep environment. You’ve got individual needs and preferences that may need individualized attention. Increasingly, sleep equipment is geared toward this level of individualization, whether for mattresses—here’s my just-released advice on choosing a hybrid mattresses—or the temperature of your sleep microclimate. 

Optimizing air quality for sleeping

The recent NASA/San Jose State study found that the optimal air quality for sleeping occurs at sea level, with ventilation. Air quality in our bedrooms is another aspect of the sleep environment that tends to get overlooked. You can increase the oxygen in your bedroom by opening windows. It’s great to sleep with windows open when the outdoor temperature allows. Depending on where you live and the season, falling asleep to a cool breeze from outdoors can be terrifically relaxing and sleep enhancing. There are other options for promoting ventilation in your bedroom. If you’re in a noisy environment, or when the weather is too hot or too cold for open-window sleeping, open windows before bedtime to circulate air and enrich the oxygen in your sleep space. Leaving doors open to your bedro and throughout your house will increase ventilation, as will fans and air conditioners. Keeping plants in the bedroom—and throughout your house—is another natural, low-cost, easy way to boost oxygen levels. Plants pull carbon dioxide from the air, and can also filter out harmful chemicals. If you have pets and/or small children, do your research to identify what plants are toxic when ingested, and take care to place plants out of reach.

THE TAKEAWAY: The farther you are from sea level, the more you’ll need to pay attention to enhancing the oxygen levels in your sleep environment. Ventilate your bedroom as much as possible in ways that don’t introduce other interference with your sleep. Open windows and leave doors open when you can, and use fans and A/C to keep air moving.

Pre-bedtime light will disrupt your sleep—but not all light works the same way to suppress sleep

The San Jose State/NASA study of optimal sleep environments confirms what I talk about a lot here: inappropriately timed light exposure in the evening hours before bed has a significant negative effect on your ability to

• fall asleep
• stay asleep
• get the optimal amount of time in each of the stages of sleep
• stick to a consistent sleep schedule, night after night

Poorly timed light exposure exerts a disruptive effect on sleep in several ways. Light is arousing. It stimulates the brain. That’s the opposite of what we want when we’re going to bed. And when your light exposure comes along with mentally stimulating content—say, from reading social media or the news online, or watching a fast-paced TV show—you’re getting a whole other layer of stimulation that takes your brain in the opposite direction from sleep.

Light at night also throws off circadian clocks—the body’s pacemaker, which regulates our daily sleep-wake cycles, and suppresses melatonin. These effects push sleep back to later in the night and they alter sleep-wake routines for nights to come.

But not all light has the same effect on sleep. Blue light—the short-wavelength light found in high concentrations in digital devices—is especially aggressive in disrupting sleep. For example, the researchers point to a study showing that use of e-readers before bed is linked to longer time to fall asleep, and less time in REM sleep compared to reading a paper book by lamplight. The blue light from e-readers was shown to suppress melatonin, shift circadian rhythms, and stimulate the brain, resulting in less sleep and more next-day fatigue, with less next-day alertness.

THE TAKEAWAY? Limitations on light are essential to protecting sleep and creating an optimal sleep environment. Your bedroom should be dark for the duration of your sleep. No phones lighting up on the nightstand, no environmental light flooding in from outdoors. But your movement away from bright light—and especially blue light—needs to start before bed. That involves both limiting overall light exposure AND employing longer-wavelength light in your nighttime light sources. Red light, studies show, does not suppress melatonin and disrupt circadian timing as blue light does. You can easily install red light bulbs in your bedroom and in the areas of your house where you’re apt to hang out before bed.

Look, I know that asking people to stash their digital devices and turn off the TV at dusk is unrealistic. It’s a habit few people can actually sustain—myself included! That’s why I spent a bunch of time working with the smart folks at Luminiere to create blue-light blocking glasses, which filter out the blue light that’s keeping you up at night. They’re made with amber lenses let those longer, red light wavelengths through, while they block the sleep-disruptive blues. These glasses don’t darken your vision. They help you see at night with aid of the long-wavelength light that studies like this recent one by NASA show does not disrupt your sleep. Here’s where you can read up on all the details of what went into making these blue light blocking glasses, and why they’re so effective in protecting your sleep without having to give up on Netflix, some evening work on front of the computer or a little social media time before bed. (Just make sure you stash your phone outside your bedroom when it comes time to sleep.) And here’s where you can check out the blue light blocking glasses in all their cool, retro style.

Curating a restful sleep environment is one of the most rewarding and effective ways to protect and enhance your sleep. An investment of time and attention to your sleep space makes going to bed feel like a reward, and pays dividends in the form of deeper, sounder, more restful and restorative sleep.

Sweet Dreams,

Michael J. Breus, PhD, DABSM

The Sleep Doctor?

www.thesleepdoctor.com