By Dr. Robert Oexman, Director of the Sleep To Live Institute
In the fall issue of Sleep Retailer, Dr. Oexman outlined 10 interesting sleep facts. This time around, he takes a closer look at one very important aspect of sleep: temperature.
The sleep and wake cycle that we move through every day is mediated by a process called the circadian rhythm: a 24-hour process that picks up cues from external stimuli like daylight and serves as an “internal clock”. One of the primary markers of this cycle is temperature. As most people probably already know, human core body temperature normally averages around 98.6°F. What most people don’t realize is that their core body temperature does not stay constant throughout the day.
As the evening approaches, core body temperature begins to drop and drowsiness increases as the transition to sleep begins. It will continue to drop over the night until early morning when it will begin to rise again. It naturally has a brief dip in its temperature during the afternoon before it rises to its peak at the end of the day, to start all over. The afternoon dip is felt by most people who will get tired after lunch and in some cultures, naps prevail during this “siesta” time of day.
At night, the temperature under the covers can affect this cycle, resulting in a decline in sleep quality. According to most studies, the best near-body temperature under the covers that is required for good sleep is around 85.1°F: termed the “thermal neutral zone” (a near-body temperature range that allows the body to maintain it’s internal temperature easily).
One study found that the thermal neutral zone was consistently maintained under a standard (two sheets and a wool blanket) set of covers while the room temperature was between 66.2° and 71.6°F. Sleep to Live recommends a more conservative range of 68°– 70°F for the bedroom temperature; however, varying numbers of covers and different types of linens can make for a borderline range from 65°–73° reasonable.