Their natural variation in sleep patterns, coupled with light or restless sleep in older adults, is enough to ensure that at least one person is on guard at all times. (sciencedaily.com)
I never sleep in, but I've been getting 9 - 10 hours of restless sleep per night the last week or so. (fashioninflight.com)
The default normal setting conveys the sleep you wish you had gotten the night before and too often doesn't pick up blatant walking around, counting it as restless sleep. (techradar.com)