Heart rate can often vary widely during REM sleep.
The heart rate during sleep should generally be slightly lower than the normal resting heart rate during wakefulness, because the body normally relaxes very deeply during sleep. When a person begins to fall asleep, their heart rate begins to slow, and studies suggest that this process can begin as soon as a person knows they are getting ready for bed. As the body relaxes into a state of deep sleep, core body temperature can drop and metabolism often slows in addition to heart rate. Your fitness level, age, and recent stress levels can influence your heart rate during sleep. However, most experts believe that the normal heart rate during sleep should be eight to 10 percent lower than the normal resting heart rate during wakefulness. A heart rate during sleep that is not at least 8% lower than your normal resting heart rate while you are awake can be a red flag.
As the body enters a state of deep sleep, the core body temperature drops and the heart rate slows.
There are at least five stages of sleep, and the heart rate during sleep can vary in each of them. The first four stages of sleep, generally classified as stages one through four, occur as the body relaxes deeper and deeper. This physiological relaxation process accounts for approximately 80% of most people’s sleep time. Heart rate typically starts to slow when sleep begins in stage one, and slows further as the body becomes more relaxed.
Heart rate during sleep can vary in each of the five stages of sleep.
Heart rate can often vary widely during REM sleep, the fifth stage of sleep during which sleep usually occurs. Rapid eye movement (REM) sleep is so named because the sleeper’s eye movements are usually visible to any observer. Physiological states can vary widely during REM sleep, possibly depending on the sleeper’s emotional reactions to their dreams. The heart rate can increase considerably during REM sleep and can even exceed the normal resting heart rate during wakefulness. The respiratory rate may also increase and other physiological functions, such as sweating, may occur.
Normal heart rate during sleep should be 8-10% lower than normal resting heart rate during wakefulness.
Some evidence suggests that heart rate during sleep may be a good indication of possible mortality in the next seven years of a sleeper’s life. An Israeli study suggests that people who do not experience at least an eight to ten percent reduction in heart rate during sleep may be up to two and a half times more likely to die in the next seven years of their lives. The study also seems to suggest that people with chronic conditions such as diabetes, hypertension and obesity are likely to experience the least reduction in heart rate during sleep.