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It’s Cool to Catch Zzz’s: How Body Temp and Sleep are Related

Most of us know that a fever can indicate sickness, but did you know that body temperature can fluctuate naturally? An example of this is during sleep. To embrace overnight rest, the body is designed to modify its temperature slightly. But when your temperature swings too much, getting a full night’s rest may be happening only in your dreams! Body temperature and sleep are closely related. Continue reading to find out what’s considered ‘normal’ and how to better understand your body’s built-in thermometer.

A Cooler Core

Mammals – that includes humans – typically require a cooler core temperature during sleep. Scientists believe that this is a way for the body to conserve energy. Think of it as putting your computer in ‘sleep mode’ – the computer stays on and ready to go at a moment’s notice, but it saves energy until it’s time for activity again. From an evolutionary standpoint, saving energy would be really important for humans with hunter-gatherer lifestyles.

It’s important to note that core body temperature is different from skin temperature. Core temperature refers to internal body temperature. Your skin may feel warm or cool to the touch, but core temperature is what really needs to fluctuate during sleep.

In fact, skin temperature may rise a bit in order to help the core temperature drop. The body can regulate this by adjusting blood flow to the skin, adjusting how much the skin sweats, and adjusting hormone levels. All of these things can help warm up the skin temp and lower the body temp to reach the ideal core temperature range.

Circadian Rhythm Triggers the Change

How does the body know when it’s time to adjust core temperature and drift off to sleep? The circadian rhythm is responsible! That’s the same internal body clock that regulates wakefulness and sleep cycles throughout a 24-hour period. A properly functioning circadian rhythm will begin dropping the body’s core temp in the evening in order to promote sleep. Then, once you’re actually sleeping, it continues to drop the temp further and keep it in the proper range until the morning.

Possible Sleep Disrupters

In some cases, poor sleep can be linked to the body’s inability to reach and maintain a cooler core body temp. There are many possibilities for why this may happen, including:

• Room is Too Hot – Because the body associates warm temps with wakefulness, a hot bedroom may inhibit the body’s ability to take cues from its circadian rhythm. The fix may be as simple as turning the thermostat down when you go to bed.

• Bedding Stops Sweating – Remember, sweating is one way that the body cools its core. If bedding or pajamas don’t allow easy sweating, the body may not be able to cool itself as efficiently.

• Room is Too Humid – Likewise, a room with high humidity may interfere with the body’s ability to sweat and lower its core temp.

• Underlying Health Condition – Some conditions, including diabetes and obesity, can mess with the body’s ability to regulate temperature. Hormonal changes, such as those during menopause, and certain medications can disrupt temperature, too.

Now you know – it’s cool to get good sleep!

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Dr. Candice Seti


California-licensed Clinical Psychologist, Certified Nutrition Coach, and Certified Personal Trainer

Dr. Candice Seti

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