Once your mattress has body impressions, there's no sure way to undo the wear and tear. However, there are a couple of things you can do to make your bed more comfortable and supportive.
Try rotating your mattress. The heavier half of your body, namely your head and torso, is what causes body impressions. By rotating, you move the indentations to the foot of the bed and once again have an even sleep surface.
Buy a mattress topper. These are comfort layers you purchase separately from your mattress and lay on top of your bed. This extra 2-4 inches of cushion helps even out the body impressions in your mattress.
If neither of these solutions work for you, it may be time to invest in a new mattress. Proper support is vital for your sleep health, so don’t cut corners when it comes to your mattress.