How does temperature affect sleep?
Two words - Temperature Dependence.
Let me break it down.
The circadian clock is a cluster of thousands of cells found in the hypothalamus area of the brain. A nerve tract connects these cells to the retinas in your eyes. Based on communications between the two, you follow a 24-hour cycle of sleep and wakefulness known as the circadian rhythm.
During the day, your eyes perceive natural light and transmit a signal indicating that you should be awake. This stimulates production of cortisol, a hormone that induces feelings of alertness. Your core temperature also remains steady during the day in order to keep you energized.
As daylight fades and evening begins, the pineal gland in your brain releases melatonin (another hormone) to make you feel tired and relaxed. The period of inactivity that follows lowers your rate of metabolic heat production, which in turn causes your body temperature to gradually decrease. As a result, these changes to your core temperature coincide with feelings of sleepiness.
This loss of body heat helps you fall and remain asleep throughout the night. Most people begin shedding body heat about two hours before they go to bed and maintain a reduced body temperature while sleeping.
Some tips for Temperature Dependence:
Set your bedroom thermostat. While 65 degrees Fahrenheit is considered the best sleep temperature, most experts agree 60 to 67 degrees is a reasonable range for most people.
Invest in a good fan. Even if you rely on an air conditioner in your bedroom, a fan will circulate air for added cooling.
Take a hot bath before bed. This may seem counterintuitive, but lying in hot or warm water can actually help you sleep cooler. Not only are baths relaxing, but your body temperature will dip as soon as you leave the tub and this can promote feelings of sleepiness.
Consider blackout curtains. They are designed to block outside light, which helps promote sleep.
Experiment with layers. Light bedclothes can provide good insulation against the cold without making you overheat, while sleeping naked can help your body maintain a lower temperature in hot and humid climes.