A wristband (Fit Band) that monitors sleep and heart rate variability (HRV)

Sleep quality is extremely important. When a person has worries in their mind, they often cannot sleep well, which leads to low energy and may affect intelligence and mood. This condition makes depression easy to occur. Good sleep quality means entering deep sleep. Generally, only two hours of deep sleep per day is enough to feel refreshed.

Moreover, sleep disorders include insomnia, which should not be treated by merely addressing the symptoms. Unfortunately, most people do not seek to find the underlying causes but immediately see a doctor, who often prescribes sleeping pills. Long-term use of such medication may form a fixed pattern of thinking and living, making future changes difficult.

Finding the underlying causes of sleep disorders requires patience and covers a wide range of factors. The key is self-care. Everyone in life faces worries and difficulties. Some people are more prone to anger or sadness, as if they have two buttons—joy and sorrow—that others control without their awareness. Strengthening self-control, avoiding impatience, and broadening the mind are important.

Bipolar disorder results from overactive sympathetic nerves, causing chronic insomnia; conversely, psychological fatigue and lack of enthusiasm for life occur when one cannot regulate properly. Everyone should find their own “balance point.” While excessive stress is harmful to health, having no stress or nothing to do is also not good. This balance point should be adjusted according to age, habits, and training.

This “balance point” is the balance between the autonomic nervous system’s sympathetic and parasympathetic nerves.

The sympathetic nervous system excites and arouses a person, mainly to cope with emergencies. The parasympathetic nervous system calms this state, allowing rest and energy storage. If autonomic nervous dysfunction is suspected, it is advisable to consult a professional and conduct a Heart Rate Variability (HRV) test.

HRV is an indicator of overall autonomic nervous function and covers all variations in normal heartbeat intervals. Total Power (TP) includes the sum of High Frequency (HF), Low Frequency (LF), and Very Low Frequency (VLF) components. HRV testing is a way to evaluate overall heart variability.

• High Frequency (HF): 0.15-0.4 Hz, represents parasympathetic activity.

• Low Frequency (LF): 0.04-0.15 Hz, represents both sympathetic and parasympathetic activity.

HF (%) = HF / (TP − VLF), the percentage of the high-frequency component, indicates parasympathetic nerve activity. Usually, values below 20 are abnormal and require attention.

LF (%) = LF / (TP − VLF), the percentage of the low-frequency component, indicates sympathetic nerve activity. Values above 80 are considered abnormal and require monitoring.

LF/HF ratio reflects the balance between sympathetic and parasympathetic activity. Values above 3 are abnormal and should be observed carefully.

Note: Normal HRV values vary with age, gender, and diseases. The above reference ranges are for guidance only.