Sleep is an incredibly complex function that our bodies requires to rest and repair. When we have problems with sleeping, this doesn’t just affect our mood but can have long term health effects including impacting our cognitive function, immune system, increased hunger leading to increased risk of obesity, and increased risk of heart disease and cancer amongst other things. When sleep is disturbed, our autonomic nervous system is often disrupted- this includes involuntary functions including temperature regulation, heart rate variability , respiration, sexual arousal, and bowel and bladder functions.
The autonomic nervous system includes the sympathetic, parasympathetic and enteric nervous system, and it allows the body to respond to external and internal stimuli by balancing the sympathetic and parasympathetic systems. When we start to feel drowsy and sleepy, our parasympathetic nervous system is activated via increasing vagal tone. As we move from NREM (non rapid eye movement) sleep to deeper stages, this is further activated and our heart rate and blood pressure reduces (van der Bourne et al). During different phases of our sleep, we alternate between NREM and REM sleep with our parasympathetic nervous system being more predominant in NREM and sympathetic in REM sleep.
When we are under stress, particularly chronic stress, our sympathetic nervous system is more activated than normal, especially if we are in flight, fight or freeze mode. This means it will be harder for the parasympathetic nervous system to be activated, which contributes to heart rate slowing down which helps us to get to sleep. Activating the vagus nerve can help to calm the body and allow the heart rate and blood pressure to fall, which can help us to sleep.
Meditation, humming, chanting and yoga can all support indirect vagus nerve stimulation. But this all takes some sort of active action to support yourself and help to reduce symptoms of stress. Stimulating the vagal nerve using a device such as Sensate, which provides skin contact vibrations, and auricular (ear based) activation through particular series of sounds can support sleep (Capone et al). Measuring our heart rate variability during sleep and heart rate itself along with the different phases can help to show whether this technique is supporting better quality sleep. Anything that increases vagal tone during the day can help us to sleep better, and improve many aspects of health.
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