I find two particular instances when someone is sleeping uncomfortably on a high mattress.
1) When the mattress is fairly new.
2) When the one sleeping is an older person.
With a new mattress, especially a firmer type, the solution for achieving comfort is quite simple in that, over time, the mattress will eventually compress to follow the shape of your body. I’ve noticed this with almost all new mattresses. There’s like an adjustment period of at least two weeks.
But when it comes to older people, the solution is a lot more than just waiting it out. The problem basically lies in the fact that older people may find getting in and getting up from a high mattress physically straining. You can remedy this by changing the level of the actual bed frame. If it’s possible to lower this, then do so. For some, putting the mattress on the floor itself works even better.
Older people can slip or fall when the mattress or bed is too high. Take safety measures as well by putting a thin layer of mattress by the floor. This can be a yoga mat or a mattress topper, which you can keep away during the daytime.
Do you have other helpful solutions for mattresses that are just too high for comfort?