Normal Heart Rate While Sleeping: What to Expect
Normal Sleeping Heart Rate by Age
Sleeping heart rate follows the same age trends as resting heart rate — higher in children, gradually settling into adult ranges by adolescence.
| Age Group | Normal Sleeping HR (bpm) |
|---|---|
| Infants (1–11 months) | 70–100 |
| Toddlers (1–3 years) | 60–90 |
| Children (4–12 years) | 55–85 |
| Teenagers (13–17) | 45–70 |
| Adults (18–60) | 40–60 |
| Older adults (60+) | 45–65 |
| Trained athletes | 30–50 |
A rough estimate: sleeping HR ≈ your resting HR minus 10–20 bpm. If your resting HR is 70, expect 50–60 bpm during sleep.
How Heart Rate Changes Through Sleep Stages
Heart rate does not stay constant throughout the night — it fluctuates with each sleep stage.
NREM Stage 1 & 2 (Light Sleep)
Heart rate begins to drop soon after falling asleep. During light NREM sleep, HR falls to roughly 5–10% below waking resting rate. Breathing slows, body temperature drops slightly, and the parasympathetic system begins to dominate.
NREM Stage 3 (Deep / Slow-Wave Sleep)
This is the most restorative phase. Heart rate reaches its lowest point of the night — often 10–30% below your daytime resting rate. Blood pressure also drops significantly. This is when cardiovascular repair and recovery occur.
REM Sleep
During REM (rapid eye movement) sleep — when most vivid dreaming occurs — heart rate becomes irregular and can spike temporarily, sometimes matching or briefly exceeding waking resting rate. This is completely normal. The body's motor neurons are suppressed, but the brain is highly active.
Is 45 bpm Normal While Sleeping?
Yes — 45 bpm during sleep is normal for most adults, especially during deep NREM sleep. For athletes and highly fit individuals, sleeping heart rates of 35–45 bpm are entirely expected. As long as you wake feeling rested and have no symptoms of dizziness or fatigue, a low sleeping HR is a positive sign.
What Causes a High Heart Rate During Sleep?
A consistently elevated heart rate during sleep (above 80–90 bpm) may indicate:
- Sleep apnea — breathing interruptions activate the sympathetic system repeatedly throughout the night
- Fever or illness — metabolic demands increase HR
- Anxiety or stress — elevated cortisol maintains higher sympathetic tone
- Alcohol or stimulants — both disrupt normal sleep HR patterns
- Atrial fibrillation — irregular elevated HR at night warrants evaluation
- Overtraining syndrome — paradoxically raises resting and sleeping HR in athletes
Tracking Your Sleeping Heart Rate
Wearable devices (Apple Watch, Garmin, Fitbit, Oura Ring) can track heart rate continuously during sleep. Over time, trends in your sleeping HR are more informative than any single reading:
- Rising trend over days/weeks possible illness, stress, or overtraining coming on
- Falling trend fitness improving, recovery on track
- Highly irregular possible atrial fibrillation, worth a medical check
Seek evaluation if your sleeping heart rate is consistently above 90 bpm, if you wake with palpitations or chest discomfort, if your partner notices you stopping breathing during sleep, or if your wearable frequently detects irregular rhythms.
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This article is for informational purposes only and does not constitute medical advice, diagnosis, or treatment. Content is based on published peer-reviewed research and has not been independently reviewed by a medical professional. If you have concerns about your heart rate, breathing, or cardiovascular health, consult a qualified healthcare provider.