How do mattresses affect sleep?
Discover how the size, firmness and materials of your mattress can make or break a good night's shut-eye
When we review mattresses here at Expert Reviews, one of the key things we look at is how well they allow us to sleep. The best mattresses keep us cool and comfortable enough to sleep soundly, and will even absorb the movements of a restless partner.
That said, how a mattress affects your sleep will differ from person to person. For example, a firm mattress can help or hinder, depending on things like the position you sleep in. So, the key to a good night’s sleep is to find the right mattress for you and your sleep style.
We’ve tested more than 40 mattresses by sleeping on them and, in this article, we share our expert insights into how different mattress types can affect the quality of your sleep. We’ll also get the latest word from sleep specialists on why your mattress choice can dramatically boost your chances of getting a full night’s rest.
Are firm or soft mattresses best for sleep?
There’s no universal answer to this question, but both independent studies and our own experience suggest that a medium-firm mattress is the best choice for good sleep.
“Research involving several volunteers found that medium-firm mattresses improved their sleep quality by 55%”, says Carolina Goncalves of UK pharmacy site Pharmica. “This is likely due to an optimal balance of support and cushioning, which also helps to prevent joint and back pain.”
Finding the proper balance between cushioning and support will help you sleep better because it allows your spine to align when you lie down. If the mattress is too soft or sagging, your hips and shoulders will sink too far into the bed, whereas a mattress that’s too firm won’t accommodate the curves of your body – if you’ve ever tried sleeping on the floor, you’ll know how uncomfortable that can be.
Unfortunately, there’s no single firmness that will fit all types of sleepers. Some people struggle to sleep unless they’re on a very soft or a very hard surface, while others can sleep anywhere. The challenge is to work out what suits you best.
If you’re a larger person, you’re more likely to require a firmer mattress than a smaller person, in order to receive the kind of full-body support you’ll need for optimal comfort. A firm mattress may also work best for you if you suffer from conditions such as back pain. But you may simply prefer a firmer mattress because that’s what you’re used to.
In our experience, what usually determines how well you’ll sleep on a firm, medium or soft mattress is your sleeping position:
Side sleepers tend to need more cushioning than back or front sleepers because their hips, knees and shoulders – the “pressure points” – need to be able to sink into the sleeping surface. If the mattress can’t accommodate your pressure points, you may find yourself tossing and turning because you can’t get comfortable.
The softer side of the double-sided Eve Wunderflip Premium Hybrid (£1,099 for a king size, pictured below) would be a good choice for side sleepers in need of that extra cushioning. For more, see our roundup of the best mattresses for side sleepers.
Back and front sleepers need support more than cushioning, particularly compared to side sleepers. A well-cushioned mattress is likely to make you feel smothered if you’re sleeping on your front, while sleeping on your back may make you feel that you’re sinking bottom-first into your bed. Either way, you’ll struggle to sleep comfortably.
The Origin Hybrid (£629 for a king size) is one of the firmer mattresses we’ve reviewed. Our reviewer noted that side sleepers may find it too hard, but if you usually sleep on your front or back, you’ll welcome the extra support. See our roundup of the best mattress for front sleepers.
If you share your bed with someone who prefers a different firmness to you, it’s worth knowing that you can get mattresses where each side has a different tension (with or without a zip running up the middle) such as Dormeo’s Dual Core mattresses.
READ NEXT: Best mattress for heavy people
Will a cooling mattress help me sleep better?
Temperature is a crucial factor affecting sleep. Too hot and you can feel uncomfortable and restless, and since a drop in your core body temperature coincides with the production of melatonin – the so-called “sleep hormone” – the optimal room temperature for sleep tends to be around 18.3°C. This can vary between people by as much as a couple of degrees, but doctors recommend setting your nighttime thermostat no higher than 20°C to help you drift off and then stay asleep through enough cycles of REM sleep and deep sleep to wake up feeling fully rested and refreshed.
Several of the best mattresses we’ve reviewed in recent years contain special layers and breathable materials that have been designed to regulate temperature to help you fall asleep comfortably, and avoid waking up in the night sweaty and clammy. It’s important to note that no mattress can actively reduce your body temperature – it’s not like putting your sheets in the fridge – but the best cooling mattresses should help prevent you from overheating. So, if you tend to get too warm at night, one of these mattresses could revolutionise your sleep.
What materials should I look for in a cooling mattress?
In general, mattresses made with breathable materials will help keep you cool, while more dense or synthetic mattresses will be warmer. Here’s a brief summary:
Springs: Whether they’re open-coil springs, individually-wrapped pocket springs or the layer of springs that you’ll often find in a hybrid mattress, springs create plenty of room inside your mattress, allowing air to flow. This makes fully sprung mattresses incredibly breathable, and significantly improves the breathability of hybrid mattresses.
Memory foam: The viscoelastic polyurethane foam – AKA memory foam – used in foam and hybrid mattresses has a poor reputation among hot sleepers because it has a tendency to retain body heat. This exaggerates the warmth of your bed and can seriously interfere with your sleep, as we’ve discovered when testing certain foam and hybrid beds-in-a-box.
However, manufacturers are developing new foam products to combat this problem. The new Emma NextGen Cooling hybrid mattress (£1,259 for a king size) has a layer of “ThermoSync” foam that’s infused with graphite to help dissipate heat. In our tests, using a heat pad and thermocouple, the mattress held onto less body heat than other hybrids and we found that it delivered a comfortable sleep, even on the hottest summer nights.
Wool: Natural materials are better at regulating temperature and letting the air flow than synthetic materials. Wool is a particularly good choice because its insulating properties help to keep you warm in winter and cool in summer.
One of the best mattresses we’ve ever reviewed, the Simba Hybrid Pro (£1,249 for a king size), features a layer of natural wool just below the sleeping surface (pictured below). As well as keeping our reviewer at a pleasant temperature all year round, the wool also enhances the mattress’s cushioning for a superbly comfy sleep too.
Bamboo: A sustainable natural fibre, bamboo wicks moisture and lets your skin breathe, so it’s a popular choice for bedding and clothing, as well as mattresses.
In our rundown of the best cooling mattresses, we gave the top spot to the Otty Pure Hybrid Bamboo and Charcoal Mattress (£850 for a king size), which our reviewer called the “coolest-feeling bed-in-a-box mattress I’ve tested”.
Latex: Another natural material, latex has an open-cell design that allows for air circulation and breathability. It’s frequently praised as a cooler alternative to memory foam, but it’s more expensive, so less likely to be found in most bed-in-a-box hybrid mattresses.
Does a bigger mattress mean better sleep?
A huge bed may be the dream for many, but would it actually improve your sleep? Sleep expert Carolina Goncalves of Pharmica thinks so.
“The size of a mattress can significantly improve sleep quality”, Carolina says. “A larger mattress reduces the likelihood of feeling cramped, allows the body to stretch out fully and minimises the risk of stiffness or joint pain.”
Then there’s the small matter of the person you’re sleeping next to. The disruption caused by a partner moving around in the night is a common complaint and frequently responsible for disturbed sleep, but the bigger the mattress, the more room you’ll both have to spread out and move without waking each other up.
The size of your budget, the size of your room and the size of your bed frame will all affect the size of mattress you can buy, but the Sleep Council recommends buying the biggest mattress you can. “You should be able to lie side by side, with your arms behind your head and your elbows out, without touching”, it advises.
A king size mattress often costs less than 10% more than the corresponding double, but that bit of extra space can make all the difference to your sleep.
READ NEXT: Best king size mattresses
How else can a mattress help me sleep undisturbed?
“Motion isolation” is another big way that a mattress can improve your sleep. Simply put, this refers to how well a mattress can absorb the movements of the person – or pet – you share your bed with, so that they don’t disturb you and you both can sleep in peace.
This is especially important if your floor space or budget can’t stretch to a king size or super king size mattress.
“For individuals sharing a bed, a mattress that provides good motion isolation is essential in maintaining the integrity of their sleep cycles”, says Carolina Goncalves. “By reducing the likelihood of being woken by a partner’s movements, motion isolation aids both individuals in reaching the deeper, more restorative stages of the REM cycle.”
Different mattress types work in different ways to absorb or transmit movement:
Sprung mattresses are not good at motion isolation. The bounciness of springs can exaggerate a partner’s movements rather than minimise them. Cheap open coil mattresses are the worst offenders because the whole mattress moves when you do, meaning bed-sharers are more likely to disturb their partners.
Memory foam mattresses offer outstanding motion isolation. Foam moulds to the shape of your body, so you’re much less likely to disturb your partner when you move at night.
Foam mattresses can get quite expensive, but the Dormeo Memory Plus is an outstanding supportive mattress that only costs around £350 for a king size.
Hybrid mattresses contain both springs and foam. The springs help the air circulate and offer durable support, while the layers of foam largely absorb the bounce of the springs. This can be a drawback if you love a bouncy mattress, but if you want to share a bed undisturbed it’s a big advantage.
When we tested it, the Emma NextGen Premium (£739 for a king size) did a superb job of absorbing the movements of a partner – our reviewer and her fidgety husband slept better on the test mattress than they ever had on their sprung mattress – and we also found the mattress excelled at temperature regulation and support, making it a winning mattress all-round.
How can I make my existing mattress better to sleep on?
There’s not much you can do to make a saggy mattress more supportive other than replace it. But if your mattress is too firm or makes you too warm, a good mattress topper is an affordable way to add some cushioning and breathability.
A mattress topper is effectively like a thin mattress that sits on top of your existing mattress and under your sheets. As with mattresses, they come in a range of types and use different materials that may be the crucial factor in improving your sleep.
Woolroom’s Deluxe Wool Topper (£250 for a king size) is a silky cushioned topper that, its makers claim, is resistant to house dust mites and fungus – helping to prevent nighttime sneezing fits. We found it very effective at regulating temperature and it’s even machine washable.
The Panda Memory Foam Bamboo Mattress Topper is fairly firm but, as our reviewer found, it softens up over time. Its washable cover is naturally antibacterial and breathable. Plus, at £160 for a king size, it’s much cheaper than a new mattress.
READ NEXT: Best single mattress
How can you tell if a mattress is good to sleep on?
We hope this article has given you a better idea of the type of mattress that will give you the best possible shut-eye but, as we know from testing mattresses, it’s hard to be sure of your perfect fit until you’ve slept on it for a while.
So, a lengthy trial period is an important consideration when choosing a mattress. Nectar and DreamCloud lead the market with their 365-night trials, during which you can ask them to collect your mattress in exchange for a full refund if you find you can’t sleep as well as you’d like on it. Simba, Emma, Eve and Origin give you 200 nights, while Otty only gives you 100 nights.
It’s reassuring to know that you don’t have to commit to your new mattress forever unless you actually love it. Which is yet another reason to sleep like a baby.
