Waking up in the middle of the night is natural, according to scientists. People who have difficulty falling back to sleep after waking might be diagnosed with the sleep disorder insomnia. However, historical findings suggests that prior to the Industrial Revolution and invention of the light bulb, humans naturally slept in two four-hour blocks, called segmented or biphasic sleep, with an hour or two of being awake in between. With the ability to turn lights on and continue productivity, human sleep patterns changed. Undeveloped countries still show segmented sleep patterns as the norm. Currently, scientists are finding that patients diagnosed with insomnia are much more likely to easily fall back to sleep when they are told that waking at night is natural.
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