Even if you don’t wear a smartwatch or fitness band to track your heart rate, you can often sense your pulse fluctuating throughout the day. During your waking hours, the number of heartbeats per minute when you’re just sitting quietly is known as your resting heart rate. In most adults, resting heart rates range between 60 and 100 beats per minute.
Once you stand up and move around, your heart rate goes up. And exercise boosts it further still. Even intense emotions — fear, anger, or surprise — can cause your heart rate to spike. But what happens when you lie down to sleep? The answer differs depending on the phase of sleep: light sleep, deep sleep, or rapid eye movement (REM) sleep.
How does your heart rate change while you sleep?
“During sleep, the stimulation of your nervous system is reduced and most of your body processes slow down,” says Dr. Lawrence Epstein, associate physician with the division of sleep and circadian disorders at Harvard-affiliated Brigham and Women’s Hospital.
Within about five minutes after you drift off to sleep, your heart rate gradually slows to its resting rate as you enter what’s known as light sleep. Your body temperature drops and your muscles relax. People typically spend about half the night in light sleep. But during the next phase, deep sleep, your blood pressure falls and your heart rate slows to about 20% to 30% below your resting heart rate.
When you dream, you enter the sleep phase known as REM (also known as dreaming sleep). “Your heart rate can vary quite a bit during REM sleep because it reflects the activity level occurring in your dream. If your dream is scary or involves activity such as running, then your heart rate rises as if you were awake,” says