Quick Answer: Your sleeping heart rate naturally slows to 40--60 BPM during deep NREM sleep and rises again during REM sleep, sometimes matching waking levels. This nightly variation is a sign of a healthy autonomic nervous system and strong cardiovascular fitness.
In This Guide
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What Happens to Your Heart During Sleep
Sleep is far from a passive state for your cardiovascular system. Each night, your heart cycles through a predictable pattern of slowing and accelerating that mirrors the architecture of your sleep stages. Understanding this pattern helps you interpret wearable data, recognise warning signs, and appreciate why quality sleep is one of the most powerful tools for heart health.
As you drift off, your parasympathetic nervous system -- often called the "rest and digest" system -- takes over from the sympathetic "fight or flight" system. Heart rate falls, blood pressure drops, and your body diverts resources toward cellular repair and immune function.
Heart Rate by Sleep Stage
A full night of sleep consists of multiple 90-minute cycles, each containing light NREM sleep, deep NREM sleep (also called slow-wave sleep), and REM sleep. Your heart rate behaves differently in each phase.
Sleep Stage Breakdown
Stage 1 NREM (Light Sleep): Heart rate begins to slow as you transition from wakefulness. Breathing becomes regular and muscle tension decreases.
Stage 2 NREM: Heart rate continues to fall. Sleep spindles and K-complexes appear on EEG. This stage makes up roughly 50% of total sleep time in healthy adults.
Stage 3 NREM (Deep/Slow-Wave Sleep): Heart rate reaches its lowest point of the night, typically 20--30% below your waking resting rate. Blood pressure also hits its lowest point. This is the most restorative phase.
REM Sleep: Heart rate rises and becomes irregular, sometimes approaching waking levels. The brain is highly active and this is when most vivid dreaming occurs.
Research published in the journal Sleep confirms that healthy adults show a clear dip in heart rate during NREM that rebounds during REM. The size of this dip is associated with better cardiovascular outcomes and is sometimes called "nocturnal dipping."
What Affects Sleeping Heart Rate
Multiple factors influence where your sleeping heart rate lands on any given night. Some are modifiable; others are fixed.
- Fitness level: Trained athletes often sleep with heart rates in the 30s--40s BPM because their hearts pump more blood per beat.
- Age: Maximum heart rate declines with age, but sleeping heart rates tend to stay relatively stable in healthy people across the lifespan.
- Alcohol consumption: Even moderate drinking suppresses REM sleep and elevates overnight heart rate by 4--10 BPM.
- Fever or illness: Each degree Celsius of elevated body temperature raises resting heart rate by roughly 8--10 BPM.
- Sleep apnoea: Episodes of stopped breathing cause repeated arousal responses, spiking heart rate throughout the night.
- Medications: Beta-blockers lower sleeping heart rate; stimulants and some antidepressants can raise it.
- Room temperature: An overheated sleep environment increases both heart rate and body temperature, reducing time in deep sleep.
Normal Ranges at a Glance
| Group | Typical Sleeping HR (BPM) | Notes |
|---|---|---|
| Healthy adult (18--64) | 40--60 | Lower end reflects good cardiovascular fitness |
| Endurance athlete | 28--50 | High stroke volume; low 30s not unusual |
| Older adult (65+) | 50--70 | Slight rise due to stiffer arteries, reduced fitness |
| Teenager (13--17) | 40--60 | Similar to healthy adult range |
| Child (6--12) | 55--85 | Higher baseline than adults |
| Toddler (1--5) | 60--100 | Still developing autonomic regulation |
| Newborn (0--12 months) | 70--100 | Highest rates of any age group |
When to See a Doctor
A sleeping heart rate outside the expected range for your age and fitness level is not automatically a crisis, but certain patterns deserve attention.
Red Flags to Watch For
- Sleeping heart rate consistently above 90 BPM without a known cause
- Sleeping heart rate below 40 BPM with dizziness or fainting episodes during the day
- Sudden increase of 15+ BPM from your normal baseline over several nights
- Heart rate that never dips at night (non-dipping pattern) -- associated with higher cardiovascular risk
Medical disclaimer: If you experience frequent or severe palpitations, consult your doctor or call 911 if accompanied by chest pain, shortness of breath, or fainting.
Sleep Environment and Heart Rate
From Dorothy, Sleep Specialist at Mattress Miracle: "One thing we hear often from customers is that they started tracking their heart rate and noticed it spiking mid-night. Nine times out of ten, the culprit is heat -- either from the mattress trapping body heat or from a room that's too warm. Your autonomic nervous system is trying to cool you down and that spikes heart rate. The right sleep surface makes a measurable difference."
Keeping your bedroom between 16 and 19 degrees Celsius is associated with optimal cardiovascular recovery during sleep. A mattress with good airflow -- whether that means open-cell foam, a coil system, or a latex core -- helps maintain that thermal environment throughout the night.
Noise and light are secondary factors. Nighttime noise above 40 dB (roughly a quiet conversation) causes measurable increases in overnight heart rate, even when the sleeper does not consciously wake. Blackout curtains and a consistent sleep schedule both support better autonomic regulation and lower sleeping heart rates over time.
Your heart rate tells a story during sleep. Mattress Miracle at 441½ West Street in Brantford sees customers who use wearable data to understand their sleep. If your heart rate does not drop during deep sleep stages, physical discomfort may be causing micro-arousals. A mattress that properly supports your body lets your heart rate decline naturally. Brad can help you interpret the data. Call (519) 770-0001.
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Call 519-770-0001Frequently Asked Questions
Is a sleeping heart rate of 45 BPM normal?
Yes, for most healthy adults and especially for anyone who exercises regularly. A rate of 45 BPM during deep sleep reflects excellent autonomic function and cardiovascular fitness. If you have no symptoms of dizziness or fainting during the day, there is nothing to be concerned about.
Why does my heart rate go up during REM sleep?
During REM sleep your brain becomes nearly as active as when you are awake. The sympathetic nervous system partially reactivates, causing heart rate and breathing to become irregular and sometimes elevated. This is normal and is part of how the brain consolidates memories and processes emotions.
Can a poor mattress raise my sleeping heart rate?
Indirectly, yes. A mattress that causes overheating, increases pain, or disrupts sleep position forces your body into repeated micro-arousals. Each micro-arousal triggers a brief sympathetic response that elevates heart rate. Persistent pain or discomfort keeps the body in a mild stress state throughout the night.
Does sleeping heart rate predict heart disease?
Resting heart rate is an established marker of cardiovascular health. A consistently elevated resting heart rate (above 80 BPM awake) is associated with higher cardiovascular risk, and a non-dipping overnight pattern (when heart rate does not fall during sleep) is similarly linked to worse outcomes. However, sleeping heart rate alone is not diagnostic -- your doctor uses it alongside other indicators.
Sources
- Burgess HJ, Trinder J, Kim Y, Luke D. "Sleep and circadian influences on cardiac autonomic nervous system activity." Am J Physiol Heart Circ Physiol. 1997;273(4):H1761-H1768.
- American Heart Association. "All About Heart Rate (Pulse)." heart.org. Updated 2023.
- Shinar Z, Akselrod S, Dagan Y, Baharav A. "Autonomic changes during wake-sleep transition: a heart rate variability based approach." Auton Neurosci. 2006;130(1-2):17-27.
- Pepin JL, Borel AL, Tamisier R, Baguet JP, Levy P, Dauvilliers Y. "Hypertension and sleep: overview of a tight relationship." Sleep Med Rev. 2014;18(6):509-519.
- Tobaldini E, Nobili L, Strada S, Casali KR, Braghiroli A, Montano N. "Heart rate variability in normal and pathological sleep." Front Physiol. 2013;4:294.
Visit Our Brantford Showroom
We are located at 441½ West Street in downtown Brantford. Free parking available. Our team does not work on commission, so you get honest advice based on your needs.
Mattress Miracle -- 441½ West Street, Brantford, ON -- (519) 770-0001
Hours: Monday--Wednesday 10am--6pm, Thursday--Friday 10am--7pm, Saturday 10am--5pm, Sunday 12pm--4pm.
If poor sleep is affecting your heart rate recovery, the right mattress can make a real difference. Visit our Brantford showroom and let our team help you find a sleep surface that supports genuine rest.
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Related Reading
- Normal Sleeping Heart Rate by Age
- High Heart Rate While Sleeping: Causes and Solutions
- Heart Palpitations at Night: Why They Happen
- Sleeping Heart Rate by Age Chart