Health

Best Cooling Mattresses and the Science of Body Heat

Complete guide to understanding body temperature changes during sleep, cold mattresses, and mattresses that keep you cool at night

By Michael WilliamsAug 31, 2021 12:00 AM
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You may be unconscious while you’re sleeping but your body is anything but idle. Depending on which stage of sleep you’re in, your brain and body could be very active. Your body goes through changes in respiration, brain activity, hormone production, and cardiac activity during sleep but one of the first changes to occur is a drop in body temperature. 

Body temperature tends to fluctuate throughout the day, but it starts to decline a few hours before bedtime. Overnight, your body temperature may be 1 to 2 degrees lower than during the day, then it starts to rise in the early hours of the morning to prepare you for wakefulness. 

If you’ve ever spent a hot summer night tossing and turning, it should come as no surprise that research shows we tend to sleep better in cooler temperatures. Body temperature is closely linked to your body’s circadian rhythm (your internal clock), so when your body temperature is too high, you may have trouble falling asleep or staying asleep. 

Not only have experts determined that we tend to sleep better when we’re cooler, but they’ve also discovered the optimal temperature for sleep. 

In this article, we’ll explore the relationship between body temperature and sleep. We’ll dig deeper into the subject of body heat in general and explore the changes that occur during sleep. You’ll also learn the best temperature for sleep and receive some tips for keeping cool at night, including recommendations for the best cooling mattresses and mattress toppers. 

Why Does Body Temperature Change During Sleep? 

The human body runs like a well-oiled machine. While you may not be consciously aware of it, there are myriad systems constantly running under the surface that control everything from heart rate and respiration to appetite, digestion, and sleep. 

Your circadian rhythm – the internal clock that dictates the sleep/wake cycle – is controlled by the suprachiasmatic nucleus (SCN). According to the NIH, the SCN is a “cluster of thousands of cells that receive information about light exposure directly from the eyes and control your behavioral rhythm.” This cluster is located in the hypothalamus, a small structure located deep inside the brain. 

Essentially, your eyes detect natural light and send a signal to the SCN which triggers the production of cortisol, a hormone that helps keep you awake and alert. While you’re awake, your body temperature remains fairly stable to provide you with a steady influx of energy. 

As day turns to night, your eyes detect the waning of natural light and send another signal which stimulates the pineal gland (a small endocrine gland located in the brain) to produce the hormone melatonin which makes you feel tired. As your body starts to relax and wind down, your metabolism slows which causes your body temperature to gradually decline. 

Body Temperature Changes in the Four Sleep Stages 

A normal sleep cycle for humans consists of four separate stages, each of which is characterized by specific physiological changes. The first three stages are known as non-rapid eye movement (NREM) sleep while the fourth is rapid eye movement (REM) sleep. 

Here is an overview of each of the four stages of sleep

  • NREM 1 – This stage represents the transition from wakefulness to sleep and generally only lasts a few minutes. During NREM 1, your heart rate, respiration, and eye movements start to slow, and your muscles begin to relax. You may experience occasional twitches known as hypnic jerks during this first stage of light sleep. 

  • NREM 2 – This stage involves a period of light sleep before your body moves into a deeper state of sleep. Your heart rate and respiration continue to slow, and your muscles relax even further. Eye movements eventually stop, and your body temperature drops to its lowest point, about 2 degrees below your daytime average. Even your brain temperature declines by 0.2 to 0.4 degrees. NREM 2 is the longest of the four stages of sleep. 

  • NREM 3 – This is a period of deep sleep that occurs in longer intervals during the first half of the night then declines in duration in the second half. During this stage, your heart rate, respiration, and brain wave activity reach their lowest points and your muscles relax completely. Your body temperature remains low and may decrease a little further during this stage. 

  • REM – This final stage of sleep occurs about 90 minutes after you fall asleep. While your body temperature remains low in REM sleep, your brain activity and eye movement increase significantly. This is the stage in which dreaming is believed to occur and your body is partially paralyzed to prevent you from physically acting out your dreams. As you get older, you spend a lower proportion of your sleep cycle in REM sleep. 

Over the course of an average night’s sleep, you’ll go through this cycle four to five times, repeating the four stages every 90 to 120 minutes. By the time you wake up in the morning, your body returns to its baseline levels for body temperature and hormone production. 

What is the Best Temperature for Sleep? 

Because your body temperature declines at night, you may be more sensitive to heat or cold as you sleep. Temperature sensitivity may increase during NREM stages of sleep, so you’re more likely to wake up during these stages if you’re feeling too cold or too hot. This sensitivity decreases during REM sleep, but you could still wake up with drastic shifts in temperature. 

Everyone has their own preferences for sleeping temperature, but experts suggest the optimal temperature for sleep is somewhere between 60 and 67 degrees Fahrenheit (15.6 to 19.4 degrees Celsius). Maintaining an ambient temperature within this range keeps your core temperature from rising enough during sleep that it wakes you up. 

Why Do Some People Run Hot at Night? 

Some people simply seem to run at a higher body temperature than others and it can be a problem when it comes time for bed. Body temperature is regulated by the hypothalamus in the brain – it works almost like a thermostat, reacting to both internal and external factors in order to keep your core temperature as close to the ideal of 98.6 degrees Fahrenheit (37 degrees Celsius) as possible. 

The hypothalamus stimulates the release of hormones and other natural chemicals that work together with the various systems in your body (such as your blood vessels, skin, and sweat glands) to cool down or warm up your body as needed to maintain that ideal core temperature. 

If you tend to run hot at night, it could be an issue with the hypothalamus. There are a number of things that can throw your body temperature out of whack at night, including: 

  • Menstruation – It’s normal for women to experience a slight increase in body temperature in the days leading up to your period. Changing hormone levels are generally the cause. 

  • Perimenopause and Menopause – Menopause involves significant changes in hormone levels – particularly estrogen – which can change the amount of blood flowing through the vessels under your skin. Changes in circulation can cause your skin to flush and may trigger hot flashes. 

  • Pregnancy – Pregnant women experience surging levels of estrogen during pregnancy which can lead to changes in body temperature. 

  • Cold or Infection – As your body works to fight off a cold or infection, you may develop a fever. 

  • Certain Drugs – Some prescription medications, such as antidepressants and other psychiatric medications, can trigger an increase in body temperature at night. 

  • Medical Conditions – Health problems that affect hormone production can lead to changes in body temperature at night. Thyroid disease and certain cancers are key examples. 

In addition to these internal factors, certain external factors can affect your body temperature and your ability to sleep. The temperature in your room is a major factor, as is your choice of bedding and clothing. Even your mattress plays a role in controlling your body temperature at night. 

Tips for Getting a Good Night’s Sleep 

Whether you find yourself sweating or shivering at night, there are simple things you can do to improve your thermoregulation for a more comfortable night’s sleep. Getting a good night’s rest is essential for optimal physical and mental health – it also contributes greatly to your quality of life.   

Here are some simple things you can do to start sleeping better: 

  • Try to stick to a regular sleep schedule. The sleep/wake cycle is regulated by melatonin production and the more you stick to a consistent schedule for going to bed and getting up in the morning, the more regular the cycle will become. 

  • Give yourself 30 minutes to wind down before bed. Create a relaxing bedtime routine that starts about 30 minutes before bedtime. Avoid screens and mobile devices. Try reading, listening to quiet music, or taking a hot bath instead.   

  • Avoid exercise, caffeine, and nicotine before bed. Exercising within a few hours of bedtime can interfere with your body’s ability to wind down for sleep. Ingesting caffeine or using nicotine in the evening can have the same effect. 

  • Turn your bedroom into a haven for sleep. The best environment for sleep is cool, dark, and quiet. Use blackout curtains if ambient light is an issue, invest in a quality fan or air conditioning unit, and try using ear plugs or a white noise machine to cancel out noise. 

  • If you can’t sleep, get out of bed until you feel tired. When you can’t fall asleep, don’t simply lie in bed tossing and turning. Get out of bed, move into another room if you can, and do something relaxing for 15 to 30 minutes until you feel tired enough to sleep. 

The tips above will help you get started with developing better sleep hygiene for an improved sleep experience. While sticking to a regular sleep schedule and improving your sleep environment can certainly help, sleeping on the wrong mattress could negate your efforts. Read on to see our suggestions for the best cooling mattress and mattress toppers to keep you cool and comfortable at night. 

The Best Cooling Mattresses and Mattress Toppers 

If you tend to run hot at night, you might benefit from a cooling mattress or mattress topper that helps dissipate body heat to keep you comfortable at night. We’ve selected an assortment of the best cooling mattress and best cooling mattress toppers to help you find the one that’s right for you. 

  1. GhostBed Luxe Mattress 

  2. IDLE Hybrid Mattress 

  3. Sweet Night Twilight Hybrid Mattress 

  4. OkiOki OkiEasy Hybrid Mattress 

  5. GhostBed Memory Foam Topper 

  6. Sweet Night Mattress Topper 

  7. OkiOki Mattress Topper 

Let’s take a closer look at each of these products. 

1. GhostBed Luxe Mattress 

Named the “best cooling mattress for hot sleepers” by Sleep Foundation in 2021, the GhostBed Luxe mattress features seven layers of cooling and comfort packed into a 13-inch height. This mattress is rated medium-plush, designed to conform to the contours of your body for optimal pressure relief without compromising on support or comfort. 

The GhostBed Luxe is ideal for side and back sleepers as well as hot sleepers who desire the best in cooling sleep technology. This mattress is constructed with the following layers: 

  • A 7.5-inch layer of high-density support foam 

  • A responsive layer of Ghost Bounce material 

  • A 3-inch layer of gel memory foam 

  • A layer of patent-pending Ghost Ice material 

  • A 1-inch layer of gel memory foam 

  • A cover made from Ghost Ice fabric 

This combination of materials helps transfer body heat to keep the core of the mattress cool, ensuring optimal temperature regulation throughout the night. The GhostBed Luxe also delivers strong motion isolation, making it a great choice for couples and light sleepers. 

2. IDLE Hybrid Mattress 

Offering two sides for the price of one, the IDLE Hybrid mattress is a flippable mattress made with Idle Sleep’s revolutionary Buoyancy Foam which offers 400% more support than traditional memory foam. Paired with 1,000 smart support coils, this mattress offers a supportive sleep experience for all sleepers with the added benefit of superior pressure relief. 

The IDLE Hybrid mattress is made with CertiPUR-US Certified foams so you can sleep soundly knowing your mattress is completely safe. This mattress is constructed with the following layers: 

  • A 6-inch layer of edge-to-edge wrapped coils 

  • A 1-inch layer of supportive transition foam 

  • A 2-inch core of IDLE cooling Buoyancy Foam 

  • A 1-inch layer of contouring quilted foam 

  • A natural fire-resistant barrier 

  • A Thermocool fabric cover 

The combination of Quantum coils and Buoyancy foam supports your body’s natural thermal capabilities to keep you cool and comfortable all night long. This mattress is double-sided, allowing you to choose your preferred degree of firmness – medium or luxury firm. 

3. Sweet Night Twilight Hybrid Mattress 

Affordably priced and available in two heights, the Sweet Night Twilight Hybrid Mattress delivers the optimal combination of thermoregulation and pressure relief. Gel-infused memory foam helps dissipate body heat, slowly adjusting to your body temperature to help you sleep cool while the pocketed coil base provides the support and pressure relief you need for comfort. 

The Sweet Night Twilight Hybrid Mattress features triple-layered foam technology combined with a zoned pocketed coil system. This mattress is constructed with the following layers: 

  • A base layer of support foam 

  • A support layer of pocketed coils 

  • A layer of cooling gel memory foam 

  • A layer of airflow high-density foam 

  • A tufted foam top with a knit cover 

The Sweet Night pocketed coil base provides bouncy support for optimal spine alignment while relieving pressure where needed. Multiple layers of gel-infused memory foam add contouring benefits and strong heat dissipation to help you sleep cooler and more comfortably. 

4. OkiOki OkiEasy Hybrid Mattress 

Featuring a combination of high-density memory foam and a pocket spring core, the OkiOki OkiEasy Hybrid Mattress creates a soft but responsive feel ideal for side sleepers. Multiple layers of memory foam conform to the contours of the body for optimal pressure relief while the individually pocketed springs provide a base layer of support. 

The OkiOki OkiEasy Hybrid Mattress is made with a number of unique materials including an Ice Yarn cover which promotes airflow. This mattress is constructed with the following layers: 

  • A 1-inch base layer of memory foam 

  • A support layer of foam-encased pocket springs 

  • A 2.5-inch transition layer of high-density foam 

  • A 2-inch comfort layer of contouring memory foam 

  • A hypoallergenic Ice Yarn zip cover 

This combination of materials delivers a cool and supportive sleeping experience. The pocketed coils relieve pressure where you need it while the memory foam conforms to the shape of your body for superior pressure relief. This mattress comes with a generous 365-night in-home sleep trial. 

5. GhostBed Memory Foam Topper 

Upgrade the cooling power of your GhostBed mattress with a memory foam topper. Comprised of 3 inches of contouring and cooling gel memory foam, this cooling mattress topper features 5 zones of targeted comfort with raised zones to promote airflow. 

Complete with the signature 2” GhostGrip elastic band to keep the topper in place and a waterproof fitter cover, this mattress topper keeps you cool for a deeper, more restorative sleep while also protecting your investment. 

6. Sweet Night Mattress Topper 

Choose from three different thicknesses in the Sweet Night Mattress Topper, each made with egg crate gel foam and breathable fabric to dissipate body heat for a cool and comfortable night’s sleep. Each topper also comes with a waterproof mattress protector for an added layer of protection. 

The 2-inch Sweet Night Mattress Topper is a thin and convenient solution to add a little extra cushioning to your mattress while the 3-inch topper is ideal for those who prefer a bouncy but supportive sleep experience. If you desire a fast response and firmer support, try the 4-inch mattress topper. 

7. OkiOki Mattress Topper 

Comprised of 2 inches of ultra-responsive OkiOki memory foam, this mattress topper delivers an added layer of comfort and pressure relief. Available in all six standard sizes (Twin through California King), this mattress topper comes with a 365-night trial period and a 3-year warranty. 

The OkiOki Memory Foam Mattress Topper features motion-isolating foam with upgraded edge support as well as cooling, breathable fabric for optimal comfort. With a risk-free in-home trial, you have nothing to lose by giving this cooling mattress topper a try. 

Final Thoughts 

Getting a good night’s sleep is essential for optimal health and wellness but it can be a challenge to achieve. If you struggle to fall asleep at night, consider whether it might be an issue with temperature. Maintaining your bedroom in that optimal 60- to 67-degree range is ideal for sleep, though you may need some extra help from a cooling mattress or mattress topper. 

If you find yourself waking up in a sweat several nights a week, it may be worth investing in a better mattress. The best mattress for hot sleepers could very well be one of our top picks reviewed above – check them out to see whether one looks like the perfect fit for you. 

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