A healthy heart rate naturally fluctuates throughout the day and night, adapting to activity levels, emotions, and rest. During sleep, the body undergoes a natural slowing process, which includes a decrease in heart rate. Understanding these fluctuations helps maintain peace of mind and recognize when a heart rate warrants further attention.
Understanding Normal Sleeping Heart Rates
A typical resting heart rate for adults when awake generally falls between 60 and 100 beats per minute (bpm). During sleep, the heart rate naturally decreases as the body enters a state of rest and recovery.
During the initial stages of light sleep, the heart rate begins to slow. As an individual progresses into deep sleep, the heart rate reaches its lowest levels. This drop occurs as the parasympathetic nervous system dominates, reducing the heart’s workload and metabolic demand. For adults, a normal heart rate during sleep is often between 40 and 50 bpm, though individual variations are common.
Common Reasons for a Low Sleeping Heart Rate
A sleeping heart rate of 38 bpm can be normal for some, especially highly physically fit individuals. Athletes, particularly endurance athletes, often exhibit “athlete’s heart,” where their resting heart rate, including during sleep, can be significantly lower. This occurs because their trained hearts are more efficient, pumping more blood with fewer beats.
Beyond high fitness levels, other factors can contribute to a low sleeping heart rate. As people age, the heart’s electrical system can naturally slow down, leading to lower heart rates. The deepest stages of non-rapid eye movement (NREM) sleep are characterized by significant heart rate deceleration, with drops of 20-30% below resting heart rate being typical. This is part of the body’s energy conservation and repair processes.
Certain medications, such as beta-blockers and calcium channel blockers, can cause a low heart rate. Underlying medical conditions may also contribute to bradycardia during sleep.
- An underactive thyroid gland (hypothyroidism), which slows metabolism.
- Electrolyte imbalances (e.g., potassium or calcium), essential for heart function.
- Sleep apnea, where breathing repeatedly stops during sleep, causing oxygen deprivation and heart rate fluctuations.
- Conditions affecting the heart’s natural pacemaker or electrical pathways, like sick sinus syndrome or heart block.
When to Consult a Medical Professional
While a low sleeping heart rate can be normal for many, especially fit individuals, accompanying symptoms might indicate an underlying issue. If a low heart rate, such as 38 bpm, is consistently observed alongside symptoms, it warrants medical evaluation. These symptoms include dizziness, lightheadedness, or fainting spells, suggesting insufficient blood flow to the brain.
Other concerning symptoms include unexplained fatigue, weakness, or feeling easily tired during physical activity. Shortness of breath, chest pain, or confusion and memory problems also warrant medical attention. It is helpful to consider whether the low readings are a one-off occurrence or part of a consistent pattern. If the heart rate consistently drops significantly below what is typical for you, even without clear symptoms, it is advisable to seek professional medical advice.
A healthcare professional will review your medical history and may perform tests such as an electrocardiogram (ECG) to assess the heart’s electrical activity. Depending on the findings, further evaluations like a sleep study or more extensive cardiac assessments might be recommended to determine the cause of the low heart rate. While monitoring your heart rate can be beneficial, a professional assessment is crucial for accurate diagnosis and appropriate guidance.