Some insomnia researchers think that chronic insomnia is a disorder of the autonomic nervous system (ANS), the part of our body that controls processes that we generally are not able to consciously control - like heart rate, pupil dilation, etc. It is felt that insomniacs have an overactive ANS that makes it more difficult to sleep. One way to measure the activity of the ANS is by recording the variability of the heart rate. Specifically, the frequency of the heart rate variability has been correlated with ANS activity.
In the August edition of the Journal of Clinical Sleep Medicine, researchers have come up with a non-medication way of treating insomnia. This treatment stimulates the vestibular system, which is part of the inner ear that controls balance. In the current study, they hypothesized that heart rate variability could predict who might respond to vestibular system stimulation.
The researchers studied healthy people over two nights. They slept their normal amount on the first night. But on the second night, they made the subjects go to bed 4 hours earlier to simulate a sleep onset insomnia. Also, the subjects were randomly assigned to receive either one hour of vestibular stimulation or sham therapy on that second night before bed. The results showed that in those subjects who fell asleep faster on the second night with the vestibular treatment had different heart rate variabilities than those that did not respond to vestibular treatment. And this variability was most pronounced in subjects > 35 years old.
The study authors suggest that future research might focus on the relationship between the ANS and insomnia, and how to predict response to various insomnia therapies. This would allow sleep physicians to better treat the various types of insomnia patients - since some respond to medications and some do not. Right now, it's very difficult for us to tell who is going to respond - but the results of the current study are encouraging.
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