A DAILY DISCOVERY / Sleep and light
Why does your heart work less hard when you first drift off to sleep?
Your body naturally shifts its autonomic balance during rest. When you transition into non-REM sleep, your heart rate and blood pressure drop, giving your cardiovascular system a period of reduced workload compared to your waking hours.
Why it happens
When you fall asleep and move into non-REM sleep, your parasympathetic nervous system takes over control of your body. Under this parasympathetic dominance, your blood pressure and heart rate decline, allowing the heart to pump with less effort than when you are awake. Later, during REM sleep and the process of waking, your sympathetic nervous system reactivates, returning blood pressure and heart rate toward their relaxed daytime baselines.
Something to notice
Notice how your body physically softens and relaxes as you wind down in bed, reflecting that initial shift toward calmer rest.
Keep the context
The source notes that sleep patterns naturally shift across different sleep stages. Furthermore, sharp spikes in blood pressure and heart rate during awakening have been linked to chest pain and cardiovascular events.
Seek prompt medical care if you experience chest pain, sudden shortness of breath, or unexplained rapid heart pounding upon waking.
Sources and limits
Sleep and light
Source retrieved 2026-10-24
Written with AI assistance and checked automatically against the linked source material. This is not a clinician-reviewed article or a diagnosis. Source retrieval does not establish clinical review. Our editorial approach.