A good mattress is an essential ingredient to ensure good sleep, but not so much in the way we think. We associate mattresses with back comfort and it is true that your mattress can make a difference to whether you sleep comfortably or awaken with a sore back. But a subtler and more pervasive effect of mattresses on sleep has to do with the material of which the mattress is made – whether it absorbs and dissipates your body heat or if it allows the heat to accumulate under your body.
The circadian rhythm dictates the fact that when we sleep our body temperature falls by a couple of degrees. This fall in temperature is not critical just to the onset of sleep but also to ensure that the subsequent sleep is deep (and therefore refreshing). A common recommendation to get a good nights sleep is to have a hot water bath before going to bed. The subsequent cooling seems to aid the onset of sleep. If the temperature in the bedroom is kept low (around 20 degrees Celsius) then deep sleep is sustained for longer.
The material of the mattress you sleep on plays an important role in whether the heat generated by your body gets dissipated away thus allowing your body to remain cool or allows the heat to stagnate thus raising core body temperature. The mattress type that is highly recommended for people with bad backs – made of memory foam – is a heat trapper. It traps the heat under your body. This eventually raises the core body temperature during sleep. On the other hand cheaper varieties of mattresses that are made of polyester fiberfill covered with cotton fabric do an excellent job of wicking away body heat, helping maintain a low core body temperature during sleep. This phenomenon has been studied experimentally to show that the heat wicking mattresses (the springier high rebound mattress) promote deep sleep whereas the memory foam (low rebound mattress) types do not have this effect. Thus the mattress that is recommended for a bad back is often the worst type for good sleep. One way to solve this problem is to use a mattress topper made of polyester fiberfill.
If you live in the tropics where a ceiling fan is often used, the effect of a heat retaining mattress can be exaggerated since the ceiling fan cools the exposed surface of the body while the parts of the body in contact with the mattress underneath are at an uncomfortably high temperature (especially since the mattress temperature is closer to the high ambient temperature in the room). This sets up an uncomfortable gradient in body temperature that is worsened when the ceiling fan is blasted on full (a common reaction to the feeling of heat). A better solution in such a situation is to sleep on a cool surface, like a plain and thin cotton dhurry or even directly on the floor.
PLoS One. 2018 Jun 27;13(6):e0197521. doi: 10.1371/journal.pone.0197521. eCollection 2018.High rebound mattress toppers facilitate core body temperature drop and enhance deep sleep in the initial phase of nocturnal sleep.Chiba S1,2, Yagi T3, Ozone M2,4, Matsumura M2, Sekiguchi H5, Ganeko M6, Uchida S6, Nishino S2.