Sleep quantity is the amount of hours a person spends asleep, while sleep quality refers to how deeply one would be sleeping. Both are important. Sleep is broken into various stages through which we go multiple times a night. The stages play a role in repairing cells and preparing the body for the next day.
For a well-rested sleep, we should spend adequate time in each stage of sleep and without waking up too many times. The quality of sleep is hard to estimate; it is something which can easily be over-/under underestimated. A quality sleep cycle is critical for the mind and body. It is important for mental as well as physical health, immune system function, appetite regulation, and cell and tissue repair.
Sleep disorders such as insomnia can also interfere with performance issues, mood changes, and daytime sleepiness.
Circadian Rhythm
Circadian rhythm is the bodys internal clock, running in the background to carry out essential functions. It is important to keep a consistent routine and sleep schedule to maintain a healthy circadian rhythm.
Daytime Sleepiness
Although the afternoon slump is quite natural, waking up feeling unrefreshed after a night's sleep, or having trouble during a work day, could be signs of sleep deprivation. Sleeping on a day off is a sign that work week sleep hours are not enough, and often this can present as feeling drowsy whilst watching TV, attending class/meeting, or sitting in traffic.
Microsleep
A very sleep-deprived person may experience microsleep, in which they fall asleep for just a few seconds at a time. If this becomes a regular occurrence, people may believe they have adapted to less sleep however, it makes people more irritable, anxious, and depressed. They can also suffer from a lack of attention or decreased reaction time.