Americans of all ages struggle with feeling rested after a night's sleep. Are you sleeping too much, or too little? The problem isn't necessarily that black and white. The quantity and quality of sleep that is needed each night is determined through specifics pertaining to a person's daily life.
Many students aren't surprised when you tell them that attending college increases the incidence of both sleep problems and depression. Depression is already two times more common in the general population, affecting approximately 20% of students, and researchers believe that lack of sleep contributes to this high rate. What students often fail to realize is that sleep problems that persist for more than two weeks can actually be a risk factor for developing depression. More than 80% of people who suffer from depression also have difficulty sleeping, and if sleep problems persist after depression has subsided, the risk of relapse increases.
Afternoon naps for most people typically last between 30 and 60 minutes. Any longer and there is a risk of falling into deep sleep and having a difficult time waking. Following a nap, having dissipated some of the accumulated sleep drive, many people report feeling better able to stay awake and alert in the late afternoon and evening. This increased alertness typically causes people to go to bed later and generally to sleep less at night than people who do not take naps.
Each person’s body needs a specific amount of sleep to maintain health and to prevent feeling tired. This amount is calculated by the suprachiasmatic nuclei, which keeps careful track of the amount of sleep we get. If our suprachiasmatic nuclei calculates that we need 8 hours of sleep, but only get 7 on a particular night, it registers that it is “owed” an additional hour of sleep. This is our sleep debt. The amount of sleep “owed” is added to the amount of sleep our suprachiasmatic nuclei wants us to have each night.
The typical adult sleeps about 8 hours per night (with lots of individual variability – I personally think I need about 9 to 9.5 hours, while my dad can’t seem to sleep more than 6 or 7!). Teenagers tend to need 9 or more hours of sleep a night to be optimally alert the next day (perhaps I’m stuck in adolescence), and sleep needs continue to increase as you move backwards towards infancy. But again, its not as simple as how much sleep we need at various times in our lives, our age also helps determine what type of sleep we get.
As we move from childhood to adulthood, we experience a reduction in how much deep sleep we get (NREM Stages 3-4). This change takes place primarily in adolescence when about 40% of NREM Stages 3-4 sleep is replaced by Stage 2 sleep. In addition to losing our deep sleep, we also cut back on REM sleep as we age.
Most dreaming occurs during REM sleep. During REM sleep, a person's eyes move back and forth rapidly. Sleep researchers discovered this when they woke people up during REM sleep. Often when people in REM sleep wake up, they say that they were just dreaming. The EEG pattern during REM sleep is similar to the EEG pattern when people are awake. However, the muscle activity is very quiet during REM sleep. Muscles are inactive to prevent us from acting out our dreams. This also means that sleepwalkers are not in REM sleep and are not acting out their dreams.
In a normal night's sleep, a sleeper begins in stage 1, moves down through the stages, to stage 4, then back up through the stages, with the exception that stage 1 is replaced by REM, then the sleeper goes back down through the stages again. One cycle, from stage 1 to REM takes approximately ninety minutes. This cycle is repeated throughout the night, with the length of REM periods increasing, and the length of delta sleep decreasing, until during the last few cycles there is no delta sleep at all.
Sleep history—the quantity and quality of an individual’s sleep in recent days—can also have dramatic effects on sleep patterns. Repeatedly missing a night’s sleep, an irregular sleep schedule, or frequent disturbance of sleep can result in a redistribution of sleep stages, for instance, prolonged and deeper periods of slow-wave NREM sleep. Drugs may affect sleep stages as well. For example, alcohol before sleep tends to suppress REM sleep early in the night. As the alcohol is metabolized later in the night, REM sleep rebounds. However, awakenings also become more frequent during this time.
Did you know that you may be sleeping an average of 1–1.6 hours less than college students did a generation ago? While many adults function best with around 8 hours of sleep (and this varies depending on many variables: your environment, health, age, etc.), college students today may be averaging only 6–6.9 hours of sleep as a result of all-nighters, cramming, parties, TV, the internet, and a general overload of activity. In fact, 8 hours of sleep may seem unreasonable for many college students; residence hall life is remarkably noisy, distractions are plentiful, and you may have a job or have a family to care for in addition to school. Stress and anxiety about coursework and your personal life rob many of a decent bout of shut-eye.
One of the most pervasive misconceptions about sleep is that sleep is just a matter of our bodies "turning off" for several hours, followed by our bodies "turning back on" when we awake. In short most of us think of sleep as a passive and relatively constant and unchanging process. In fact, sleep is a very active state. Our bodies move frequently, as we roll about during the night, and, more importantly to the psychologist, our brain activity is even more varied than it is during the normal waking state.