However, some individuals are able to function without sleepiness or drowsiness after as little as six hours of sleep. Others can't perform at their peak unless they've slept ten hours. Other signs are a tendency to be unreasonably irritable with co-workers, family or friends, and difficulty concentrating or remembering facts. REM sleep is when you dream, and is characterized by a high level of mental and physical activity. In fact, your heart rate, blood pressure and breathing are similar to what you experience when you are awake.
Scientists define the best sleep as having the right mix of REM and non-REM sleep.
Getting enough sleep without interruptions from your environment or from internal factors such as your breathing is more likely to maintain your natural sleep architecture and result in restful and restorative sleep. Virtually everyone suffers at least an occasional night of poor sleep. These include students, shift workers, travelers, and persons suffering from acute stress, depression, or chronic pain. And employees working long hours or multiple jobs may find their sleep less refreshing. Older adults also have frequent difficulty with sleep problems, but inadequate sleep is not an inevitable part of the aging process.