Typical Sleep in Adolescents and Adults
Figure 1. Five ideas about why we need sleep. The truth is, there is no black-and-white answer. However, investigators have proposed that sleep serves as a way of consolidating memories acquired during wakefulness [1] and warding off metabolic harm [2].
Figure 2. Average time of each sleep stage through the night. Human sleep comprises two states that alternate cyclically: rapid eye movement (REM) when dreaming is common, and non–REM (NREM) sleep characterized by low muscle tone and minimal psychological activity. The first episode of REM sleep occurs about 80-100 minutes afterwards, and the cycle between NREM and REM sleep repeats every 90 minutes, with REM sleep episodes getting longer throughout the night. Other factors that may alter sleep include previous sleep-wake history, phase of the circadian timing system, environmental factors such as temperature, light, sounds (e.g. a partner’s snoring or teeth grinding), drugs, and sleep disorders [3].
Figure 3. Sleep recommendations across the lifespan. Deep sleep decreases across adolescence by 40%, starting from the preteen years. Recommended sleep for adolescents is eight to ten hours a night, but roughly two-thirds receive less than eight on school nights. Poor sleep quality has shown decreased academic performance/increased risk-taking behaviors [3]. Note that these numbers are general recommendations, and can vary individual to individual.
Figure 4. Reasons why technology reduces sleep onset. Increased technology use before bedtime is associated with a shorter sleep duration and waking up unrefreshed. Technology use before bed can be a sign of revenge bedtime procrastination. Other instances of nighttime technology use include being awoken at night by a cell phone and can lead to daytime sleepiness [4].
Figure 5. Five ways that exercise improves sleep. Keep in mind that every body is different! Exercise increases total sleep time, sleep continuity, and sleep efficiency, leading to less daytime sleepiness. Sleep also delays REM sleep onset and reduces REM sleep time. While data is relatively inconclusive, exercising earlier in the day may improve the quality of sleep as compared to later in the day [5], [6]. Exercising at night can potentially keep you awake due to increased body temperature. It may also be helpful to take a warm bath or shower after exercise to wind down.
Figure 6. Poor sleep quality has shown decreased academic performance and increased risk-taking behaviors. Stressful life events are directly associated with poor sleep quality. Rumination on these events can indirectly impact sleep quality. Resilience can decrease both these direct and indirect effects [7].
Figure 7. Substances-induced sleep disturbances. The most common sleep disturbance seen in all substances of use is insomnia. At all dosages, alcohol causes individuals to fall asleep quicker; however, this is at the cost of sleep quality [8, 9]. It’s important to note that individuals metabolize alcohol at different rates. For more details, see the CDC alcohol calculator.
Figure 8. Substances-induced sleep disturbances. Dependence on caffeine can cause poor sleep quality, daytime dysfunction, and a higher rate of sleep disturbances. The use of caffeine to overcome sleepiness can cause insomnia [10, 11].