There is no better sleep than when its super cool in your bedroom and you are covered with heavy blankets. What about when its hot?
This summer I stayed in a house for a week with no A/C and it was usually in the mid-80s at bedtime. I still slept under a blanket. It turns out that our need to sleep under a blanket has underlying reasons in two categories: physiological and psychological.
It is not true that our bodies remain at 98.6 degrees. Rather, throughout 24-hour day we cycle through periods of being warmer and colder within a range of about 3 degrees. Whether we are warm or cold affects our alertness. When we are hotter we feel more alert and feel drowsier when cooler.
About 60-90 minutes before your normal bedtime your body begins to cool down. As we are ready to fall asleep our bodies are typically experiencing the greatest drop in temperature. This is why having a hot shower or bath before bed is sleep inducing – the rapid cooling off that occurs afterwards is a sleep signal to your body.
During the REM cycle when we dream our body’s ability to thermoregulate is impaired. This lack of thermoregulation during REM tends to occur towards the end of our sleep cycle. As a result, our bodies are usually the coldest the hour or two before we wake up. After the REM cycle our bodies heat back up in order to prepare for waking up.
All the above taken together means that we like to sleep under a blanket because we are cooling down when we go to bed and we know from past experience that we’ll get even colder as the night goes on (recall the times you’ve woken up at 4 or 5 am freezing if you’re without a blanket).
There’s an additional physiological reason: the weight of blankets have a calming effect. Heavy blankets can stimulate what is known as “deep pressure touch” which both stimulates serotonin production and reduces cortisol production. Serotonin increases our sense of well-being and cortisol is the stress hormone which triggers the fight or flight response. Thus, production of serotonin and lesser production of cortisol leads to better sleep, a greater feeling of well-being and less anxiety. Studies have confirmed that sleeping under a weighted blanket improves sleep and can also reduce anxiety.
In addition to the physiological reasons we sleep with blankets there are also behavioral reasons. Chiefly, we’re conditioned to sleep under blankets. From the time we’re children and our parents tuck us in under the covers we’ve associated blankets with sleep. Thus, it is part of our ritual of going to bed and getting sleepy – its Pavolovian. Even if we’re in very warm clothes or going to bed in a very hot room it seems bizarre to not have a blanket.