Memory foam consists mainly of polyurethane as well as additional chemicals increasing its viscosity and density. It is often referred to as "viscoelastic" polyurethane foam, or low-resilience polyurethane foam (LRPu).
Too often in interior design, we see wall art or paintings treated as an afterthought. They're what gets dealt with last, long after the final coat of paint has dried on the walls and all of the furniture has been artfully arranged, if it gets dealt with at all.
Internet rumour mills claim that mattresses double in weight every 8 years. Probably not double but easily by several kilograms. It's well known that beds, in general, are a prime habitat for dust mites where one third of their nasty and brutish life occurs.
Many mattresses manufactured over the last two decades may actually be bad for you. The western way to health has been typically to "target and destroy" the "bad". This sometimes mean choosing the lesser of two evils. Many old mattress contains copious amounts of chemicals to produce key features such as "Anti-Static" and "Anti-Dust Mite".