How Much Do You Need to Sleep?

Sleep is a natural, recurring state of body and mind, marked by decreased awareness, increased sleepiness, decreased behavioral flexibility, decreased muscle activity and mobility during rapid eye movement sleep (REMS), and decreased interactions with the outside environment. Sleep can be induced or delayed depending upon a person’s sleep and wake patterns. It has been postulated that sleep duration and quality can affect mood, health, cognitive function, and the severity of disease in a way similar to mood and stress scales. It has also been postulated that sleep duration and quality influence how well people can remember things, a fact that could potentially lead to better patient care through identification and diagnosis of potential problems early.

Sleep stages are based on the duration and latency of each individual stage of sleep. The four stages of sleep are: Stage I – The dreaming or light stage; Stage II – The waking stage; Stage III – The waking state stage; and Stage IV – The non-sleep state stage. The term “stage” is used in a generic sense, and the stages do not correspond to specific sleep stages. For example, a person who sleeps for seven hours in Stage I has moved from the dreaming state to Stage I, but if a person repeats this cycle a week later, they may still be in Stage I or even in Stage IV.

REMS or rapid eye movement sleep is the sleep phase most related to cognitive function. Rapid eye movement sleep allows a person to work and think by moving their eyes, hands, legs, and other muscles while they are awake. REMS sleep has been linked to increased creativity and new thinking ability. Some evidence suggests that REMS sleep is linked to the formation of memories.

Sleep cycles range from six to nine hours. A “short-sleeper” usually falls asleep within four to five hours, while a “long sleeper” usually takes longer to get to bed and typically sleeps for eight to ten hours. As a general rule, people in the average lifestyle range can fall asleep in anywhere from five to seven hours, while “short-sleepers” can take as many as eight hours to reach Stage me of sleep, which is followed by Stage II, which involves falling asleep through the night, then Stage III, which includes Stage IV, which includes the REM sleep that is needed for creativity and new thinking. As a general rule, most people need about six hours of sleep each night in order to be functional the next day.

Stage I and II are the basic sleep cycles, and Stage III is the second of the seven intermediate sleep stages. Of the two stages, Stage IV is the longest, lasting about ten hours. It is also the most active. While a person is in Stage IV, they are awake and aware, but their body is still “sleepy” or slow. They can remember things well but cannot reason or think, and they are generally unresponsive to external stimuli.

As the body becomes inactive between sleep stages, it enters Stage V, which is considered the “deepest sleep” of the night. There are a decreased rate of body movement and no recollection of events during the previous stages. They are awake, but still haven’t awakened. In order to awaken, Stage V individuals must use a muscle, which is not possible during light sleep. In order to remain active during Stage V, they must awaken by using a muscle. If the body does not wake up, the brain has entered the Stage VI sleep state.