Impairment in the body's internal clock, ultimately disrupting a person's sleep-wake cycle, is just one of the potential symptoms of dementia.

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Melatonin products are usually synthetic versions of the hormone made naturally by the pineal gland, in the brain, which helps regulate the body's sleep-wake cycle.

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Sharing a bed may also reduce cytokines, involved in inflammation, and boost oxytocin, the so-called love hormone that is known to ease anxiety and is produced in the same part of the brain responsible for the sleep-wake cycle.

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Dr. Daniel Hanley, professor of neurology at Johns Hopkins Medicine, in Maryland, told CNN that VS is a coma-like state in which patients have a sleep and wake cycle, and can show reflex chewing, swallowing and blinking, but don't respond to language or stimulation.

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