Why Mattresses Sag?

Posted on May 18, 2018 by Linda Tang

Is your mattress sagging?  Yes, definitely...but, please don't toss it.  All mattresses sag from the day someone lies on it.  It's an inevitable fact due to the physical reality of gravity.  Objects compress when something heavy is placed on it.  In this case, that something is our body.  Mattress sagging refers to the compression and dipping of the area the body rests on.  The heavier the sleeper and the more frequent and longer the usage the more sagging there will be.  

Not all mattresses are created equally.  Some are more supportive and resilient to sagging than others.  As a rule, the thicker and heavier ones generally will sag less.  This is because they contain more mass than air.  For example, a brick is much stronger than a sponge of the same dimensions, and a stack of bricks is much more difficult to break than an individual one.  Needless to say, no one likes to sleep on bricks.  Common materials for making mattresses are far airier and softer, which include fibre (organic, natural or synthetic), foam (latex, poly, or memory foam), and metal springs.  When comparing two mattresses of the same fill and thickness, the heavier one sags less.  When comparing two mattresses of the same average density, the thicker one provides more support and sags less. 

Most people tend to sleep in the centre of the mattress, or if they share the bed with a partner, in the centre of their half.  The human body does not shape like a mattress, and its weight is not evenly distributed.  About 50% of our body weight is in our trunk, with the heaviest part in our pelvis area.  Unsurprisingly the sagging area is almost always along where our spines rest, with the deepest part right under our buttocks.  Over time as our body sinks slowly into the mattress, our shoulders close in, our breathing is restricted, and our spine is distorted, causing muscle cramps, pinched nerves, and misalignment.

How do you know when your mattress has sagged too much?  After all, it's not like a dishwasher that just quits working one day.  If you wake up regularly with stiffness and pain in your shoulder, back, or hip area, or numbness and feelings of pins and needles in your limbs that generally lessen as you get out of bed, move around, and stretch, then you need to take a close look at your mattress.  Move your hands around on the top as you may not be able to see.  Can you feel the dips?  

What to do about a sagging mattress?  Turning and flipping will definitely help.  However with most of today's mattress made to be thicker and heavier than ever, turning and flipping is not a viable option.  Mattress manufacturers would love to solve your problem by selling you a new mattress to replace your old one, but it's wasteful and not necessary.  You can fix your sagging mattress easily by placing a folded bath towel along the dipped trunk area.  Once you've folded the towel, sleep a night or two on it to fine tune the placement.  Then you can move the towel under your fitted sheet and mattress cover if any.  You may need to use a second towel if one is not enough. 

If you really want to get a new mattress, remember, you don't need to throw the old one out, unless of course, it's bug-infested, structurally broken, or toxic.  Place the folded towel on the dipping part of the old mattress and then put the new mattress on top of it.  The old mattress can serve as a base to absorb shock and pressure, which will make your new mattress more comfortable and last longer.