Amerisleep AS4 Mattress Review – Made For Side Sleepers?

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Amerisleep has five options in their line of memory foam mattresses that range from firm to soft and are designed to fit different sleeping positions.

The Amerisleep AS4 is the second-softest mattress they have. It is called “medium-soft” and is made specifically for side sleepers.

This review will cover everything people need to know about the Amerisleep AS4 mattress, including a full breakdown of the construction, firmness and feel, comfort, support, motion isolation, edge support, breathability, durability, and so much more.

30% Off

Amerisleep is a perfect choice if you want a memory foam mattress but also want to sleep cool. You can get 30% off Amerisleep mattresses simply by clicking the link below and using code MC30. 

Who Might Want To Pick The AS4:

  • Side Sleepers– On one’s side, people will feel the 4” of foam go to work after a second or so of delay. This top layer is very soft and, along with the transition foam, it relieves pressure on shoulders and hips. This mattress is designed specifically for side sleepers, and it works well in this sleeping position.
  • Hot Sleepers– Memory foam is not always the best at keeping people cool, but that is not the case with the AS4. The Celliant cover cools people and the bio-based foam is open-celled for increased breathability. In addition, the transition layer has air channels to cool people even further, so they shouldn’t be sleeping hot with the AS4.
  • Those Who Want That Classic Memory Foam Feel Without Getting Stuck– The bio foam layer is very responsive, so people shouldn’t feel “stuck.” They get to sink into the mattress, but it is still easy to move around and change positions. It’s also one of the best soft mattresses.

Save on the AS4 with Amerisleep mattress coupons.

The cover of a mattress is opened so you can see the inside.

Who Might Not Want To Pick The AS4:

  • Back or Stomach Sleepers– The AS4 is specifically designed for side sleepers so, if people sleep primarily on their stomach or back, they may not get the proper support with this mattress. If this is the case, people should consider the firmer model in the Amerisleep line.
  • Those Who Don’t Like That Classic Memory Foam Feel– With the AS4, you really get that quicksand, sinking feeling that comes with classic memory foam. If you have had more success with innerspring or latex mattresses, this may not be the best mattress for you.

Construction Overview

  • The mattress is 12” tall and features three separate layers of premium foams.
  • The cover is soft and thin and is made with Celliant, which is designed to keep you cool and help with recovery.
  • Then there is 4” of a very soft, Bio-Pur foam, which is a bio-based memory foam that is open-celled and is more breathable than normal memory foam.
  • Then there is 1” of an Affinity layer with Surface Modification Technology, which transitions sleepers from the soft upper layers down to the support layers below. It also has air channels, to allow for airflow and breathability. In addition, it has “zones” built in to give pressure relief in key areas like shoulders and hips.
  • Finally, there is a 7” Bio-core base support layer, which is a pretty standard base layer for an all-foam mattress available online.

Related:  Read About The Other Mattresses In The Amerisleep Line

A man sleeps on his side.

Construction Takeaways

  • The AS4 is available in Twin, Twin XL, Full, Queen, King, California King, and Split King, basically any size a consumer could want.
  • The memory foam in this mattress responds quickly, so people shouldn’t feel stuck in the mattress and it should be easier to switch positions.
  • The Celliant cover promotes cooling, the memory foam is open-celled, and the transition layer helps with airflow. Memory foam mattresses aren’t always the best for sleeping cool, but on the AS4, people shouldn’t be sleeping hot.
  • The 4” of memory foam make this a good option for side sleepers, and it should relieve pressure on shoulders and hips.
  • In addition, the transition layer is designed to help relieve pressure on key areas like the shoulders and hips.
30% Off

Amerisleep is a perfect choice if you want a memory foam mattress but also want to sleep cool. You can get 30% off Amerisleep mattresses simply by clicking the link below and using code MC30. 


I reviewed the AS4, Amerisleep’s medium-soft model.  That being said, the mattress felt like a 5/10 in terms of firmness, softer than average. It is designed specifically for side sleepers, which is why it is so soft.  Lying on my side, the pressure relief was great on the shoulders and hips. I pressed down into the 4” of bio foam, but did not hit the firmer layers beneath and bottom out.

On my back, I did feel some support on my hips, but I think a firmer mattress may be needed if you sleep primarily on your back.

On my stomach, I definitely needed an extra level of support and firmness. The AS4 is quite soft, so I felt my hips sinking in and it wasn’t the most comfortable. If someone is a stomach sleeper, they should look at the firmer Amerisleep models such as the AS2 and AS3.

In terms of feel, the soft foam layer is also fast to respond. While I did sink in, it was still easy to move around on the mattress and I never felt “stuck.”

Related: Amerisleep AS2 vs AS3

Motion Isolation

The AS4 is an all foam mattress, so I expected it to perform well with motion isolation.

During my tests, there was little motion transfer as I moved around the cup. If someone sleeps with a partner, they shouldn’t feel them moving around too much.

This makes the AS4 a good mattress for couples who don’t want to be disturbed by their partner’s movements.

Edge Support

All-foam mattresses don’t always have the best edge support. Sitting near the edge of the AS4, the mattress did collapse, but I didn’t feel like I was going to fall off.

Also, lying near the edge, I didn’t feel like I was going to be ejected from the bed.

Considering this is an all foam mattress, the edge support is decent.

People can see the edge support in the photo below.

A man sits on the edge of a bed.

Marten’s Take

Marten is a staff writer for us and has a much different body type. He is 6’7″ and weighs about 230 lbs (I am 5’9″ and 160 lbs.). Here is what he thought about the mattress and how appropriate they are for heavier sleepers.

“Normally with a mattress like this, I would press right down through that upper layer down to the firmer layers beneath, but I did not have that experience with the Amerisleep. I felt great pressure relief on my shoulders and my hips, when I was lying on my side.

On my back, my hips sunk in just a little bit, but I still felt good support. On my stomach, my hips definitely sunk in a little bit too much. If someone is my size and also sleeps on their stomach, they might want to look elsewhere.

However, if someone is my size and a side sleeper, it could be a really good choice for them.”

Marten’s experience confirms my opinion that the AS4 could be a great fit for side sleepers of all sizes. Even at his size, he didn’t press down to the firm support layers. Those 4” of bio-foam gave him the necessary pressure relief.

What Makes This Mattress Stand Out

  • If someone is a side sleeper of most any size, the AS4 should be a good match for them. The 4” of foam and the Affinity transition layer both relieve pressure on their shoulders and hips.
  • This is a great choice if people want to sleep cool. Because of the open-celled bio-foam, the air channels in the transition layer, and the cooling Celliant cover, people won’t be sleeping hot.
  • Sleepers get that great memory foam feel without getting stuck. The 4” of soft foam responds very quickly, making it easy to move around on the mattress.
  • The Celliant cover also helps with recovery, so this could be a great mattress for athletes.

Related: Best Mattresses Overall

Amerisleep AS4 Mattress
4.6 Reviewer
The Amerisleep AS4 is designed specifically for side sleepers and I can say that it worked very well when I slept in that position. I felt great pressure relief on my shoulders and hips. If you sleep primarily on your back or stomach, I would consider the firmer mattresses in the Amerisleep line.
Value (Price)4.6
Doesn't Sleep Hot4
Motion Transfer4.9
Edge Support4.5
Company Reputation4.6
Return Policy/Warranty4.8
Overall Sleep Experience4.6

How To Unbox This Mattress

The Amerisleep AS4 is a bed in a box mattress, which means it will come compressed and shipped straight to you. You will want to begin by removing the rolled up Amerisleep AS4 from its box. Then, preferably with another person’s assistance, position the roll on your bed.

Carefully cut the away the first layers of plastic until the still-compact mattress can be laid down flat.  Then, pierce through the final layer of plastic and the AS4 will expand. Simply clear away the excess plastic and allow your mattress to breathe and fully expand.


I found the AS4 to be very comfortable and supportive at the same time. It is designed for side sleepers, and I can say that the mattress is indeed a great match. That top layer is so soft, I felt nice pressure relief on the shoulders and my hips.

If someone is primarily a stomach or back sleeper, they may need a firmer mattress to give them the proper support. I would consider the firmer models in the Amerisleep line, such as the AS2 or AS3.

All Amerisleep products come with a 100-Night Sleep Trial and 20 Year Warranty.

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Joe Auer

Joe Auer is the editor of Mattress Clarity. He mainly focuses on mattress reviews and oversees the content across the site.

He likes things simple and take a straightforward, objective approach to his reviews. Joe has personally tested nearly 250 mattresses and always recommends people do their research before buying a new bed. He has been testing mattresses for over 5 years now, so he knows a thing or two when it comes to mattress selection. He has been cited as an authority in the industry by a number of large publications.

Joe has an undergraduate degree from Wake Forest University and an MBA from Columbia University.

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