To use the Sleep Cycle app, you set the alarm and lay the iPhone face down on your bed.

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In narcolepsy, the sleep cycle goes haywire.

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In a company-funded study published last year in the Journal of Sleep Research, the Zeo predicted the same sleep cycle as professional sleep equipment in a lab about 75% of the time, compared with 86% agreement for two independent professional lab measures with each other.

WSJ: Smart Alarms Decide When You Should Really Wake Up

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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Melatonin is a hormone produced in a gland in the brain, and helps maintain the natural cycle of sleep and wake.

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Maciek Drejak, lead developer of Sleep Cycle, says the app does record small movements, but when analyzing your sleep patterns, it "filters" the ones it doesn't think are relevant.

WSJ: Smart Alarms Decide When You Should Really Wake Up

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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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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Obesity increases the chances of developing sleep apnea, a condition that combines choking and waking in an exhausting, sometimes life-threatening cycle.

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