Schedules packed with academic, extracurricular, and social obligations make sleep-deprivation a fact of life for many Dartmouth students. Although college students require more sleep than most other age groups, few undergraduate students sleep for nearly the full nine and a quarter hours prescribed by Cornell sleep expert and author of Power Sleep, James Maas (1). College students use many different methods to combat their perpetual sleepiness. Two of the most popular methods for keeping students alert and productive are caffeine consumption and naps.
Consequences of inadequate sleep
Over 80% of adults consume caffeine daily through coffee or tea.
Other than daytime sleepiness, acute sleep loss correlates with decreased neurobehavioral performance such as inability to focus, poor memory retention, and decreased mood (2). Sleep-deprivation can also increase stress levels and vulnerability to disease. On the day following a night of sleep loss, there is an increase of proinflammatory cytokines, chemical messengers that help produce inflammation in the body. In addition to increased sleepiness, abnormally high levels of these cytokines are “associated with an unfavorable metabolic profile, a higher risk of cardiovascular adverse effects, and decreased longevity” (2). For many of the same reasons, cumulative sleep loss over extended periods of time can also lead to increased risk of heart attack, stroke, diabetes and depression (3).
Once college students have accumulated a sleep deficit, busy schedules and increased stress levels often make it nearly impossible for them to regain the sleep lost. Also, according to J.T. Szymczak of Nicolas Copernicus University in Poland, the popular technique among college students of catching up on the weekends is ineffective in restoring a sleep deficit (3). Therefore, since many Dartmouth students live continuously with a lack of sleep, they search for ways to limit the negative short-term effects of their sleep debt.
Consumption of caffeine to combat sleepiness
Just like college students across the country, Dartmouth students rely on caffeine, the most commonly used psychotropic drug in the world, to prevent sleepiness (4). Caffeine is ingrained in American culture, with over 80 percent of adults consuming it daily through coffee or tea (5). Americans use caffeine for a variety of reasons, one of which is the feeling of arousal or rejuvenation that the drug can create (6). Among college students, caffeine is often deliberately used for this physiological purpose.
Structure of Caffeine
Adenosine, an adenine molecule attached to a ribose sugar, is continuously created while humans are awake. As humans stay awake longer, more adenosine is created and fills the adenosine receptors in the brain (7). As increased numbers of these receptors are filled by adenosine, nerve cell activity is slowed down and drowsiness increases. However, when caffeine enters the body, it also binds to these adenosine receptors. In addition to leaving fewer receptors open for adenosine to bind, when caffeine binds to the adenosine receptors it actually has the opposite effect of adenosine; it speeds up nerve cell activity (7). When the body’s regulators notice the abnormal increase in brain activity, the pituitary gland responds as if there is an emergency and begins to produce adrenaline, which increases heart rate and blood sugar levels (7). In addition to increasing alertness and reducing sleepiness, the increased nerve cell activity and higher adrenaline levels impact human cognition (5).
Although caffeine-induced stimulation can reduce a person’s ability to complete complex tasks, caffeine can also improve performance on less engaging tasks. This is because complex tasks sufficiently stimulate the brain alone, and the addition of caffeine can cause excess stimulation, lowering cognitive performance. Along the same lines, caffeine overdoses can reduce cognitive performance. However, low doses of caffeine allow individuals, and especially sleep-deprived individuals, to better complete tasks that are not highly stimulating. In the same scenario, caffeine can increase memory recall and storage. For doses less than 300 milligrams (and higher for more frequent consumers), studies have also shown that caffeine tends to elevate mood, without increasing anxiety. (5)
Napping
Another method used by college students to combat sleepiness is taking a nap. Although the appeal of a nap is undeniable among sleep-deprived individuals, recent research suggests that napping, if done correctly, has a definite impact on alertness, concentration, and information storage, especially under sleep-deprived conditions (8).
Longer time spent awake and influences from the body’s circadian rhythm, which naturally causes humans to want to sleep during the night, depress alertness and productivity at night (9). A 2007 study by the Centre for Sleep Research at the University of South Australia found that a nap during a night shift helped to limit the decline of worker performance and alertness (9). Each participant of the study was randomly selected to engage in a thirty-minute nap during his or her simulated nightshift. During the simulated nightshift, performance was assessed using reaction time tests and sleep latency tests to quantify productivity and sleepiness. Participants who had the thirty-minute nap during their nightshift maintained more consistent performance and lower sleepiness throughout the simulated nightshift (9).
Another study conducted by the Department of Preventive and Social Medicine at the University of Otago in New Zealand, demonstrated similar results, showing that a short twenty-minute nap could help counteract performance decline among nightshift workers. In a two-week study involving male aircraft maintenance engineers, a twenty-minute nap was shown to increase performance on a computerized neurobehavioral test battery, again demonstrating success for “a short duration nap taken in the workplace to counteract performance deficits” (10). Shorter naps, usually lasting ten to twenty minutes were found as the most effective in both cases (9,10). Brief naps only allow the body to enter stage one sleep, the drifting off period, and stage two sleep, an intermediate stage between the first stage and deep sleep. Once the body enters stage three sleep or deep sleep, it becomes far more difficult for the body to wake back up. Therefore, after longer naps, many people often suffer from sleep inertia, the prolonged drowsiness feeling that the body undergoes as it transitions from deep sleep to its awakened state (11).
Studies like those performed by the Centre of Sleep Research indicate, due to the impact of sleep inertia, that naps less than thirty minutes are the most effective in the short-term rejuvenation of alertness and performance. By increasing levels of cortisol, a stress hormone produced by the adrenal gland that boosts blood sugar levels, and decreasing proinflammatory cytokines, short naps help alleviate drowsiness and lack of focus (11). Furthermore, 1996 research from the Karolinska Institute in Stockholm, Sweden demonstrated that naps tended to have stronger effects on individuals suffering from a sleep deficit, which suggested that short naps could be beneficial in restoring college students to near baseline performance and efficiency (8). Another study showed that a twenty minute daytime nap had a more significant impact on daytime sleepiness than adding an extra twenty minutes on to a longer nighttime sleep (12).
Another important outcome of napping among college students is its influence on memory retention. Sleep plays a vital role in the transfer of information from short-term to long-term memory. Sleep-deprived individuals do not translate information from short-term memory to long-term memory as well as they would with better rest (13). However, naps can actually provide some of the benefits of a longer night’s sleep in much less time. Napping can help to consolidate information into the declarative memory, the part of the long-term memory used to recall explicit material like facts and past experiences (13). Although naps may seem counterproductive when trying to study or memorize material, naps “appear to facilitate the formation of direct associative memories” and can even help the brain form complex relationships between data that it would not have created while awake (13).
The caffeine nap
Longer time spent awake influences the body's circadian rhythm
Studies from the Sleep Research Laboratory of Loughborough University in the United Kingdom suggest that naps and caffeine can be combined to combat sleep deprivation in a way that can be more effective than either used separately. Twelve graduate students with healthy sleeping patterns participated in an experiment in which they performed weekly two-hour simulated driver tests that measure afternoon sleepiness by counting the number of at risk incidents during two hours. When the participants were limited to five hours of sleep the previous night, there was an increase in sleepiness as detected by the simulated driver test. In following weeks, the participants were randomly selected to take thirty-minute breaks between a preliminary fifteen-minute driving period and the longer two-hour session. During the thirty-minute breaks, some participants consumed caffeine and took a nap, some participants only consumed caffeine, and others did neither (placebo). The results from the experiment indicated that caffeine consumption followed by a brief fifteen to twenty-minute nap was the most effective way to keep drivers alert and lower risk incidents like swerving out of a lane. In the each half-hour section of the two-hour driving test, the participants with the caffeine and nap performed, on average, significantly better than the participants who only consumed caffeine (who performed significantly better than the placebo group). Since it takes nearly 20 minutes for the body to feel the physiological effects of caffeine consumption, a short nap during that time period allows an individual to receive the best of both methods (13).
Summary
Many Dartmouth students are engaged in a daily battle to get the appropriate amount of sleep. Taking naps and consuming caffeine are two of the most common methods that Dartmouth students use to help limit the negative effects of their lack of sleep. Caffeine, a stimulant usually consumed through certain beverages, binds to adenosine receptors in the brain and causes increased nerve cell activity and production of adrenaline (7). These two physiological effects stimulate the brain and influence human cognition and emotions. Caffeine can help elevate mood and also, especially for less stimulating tasks, increase cognitive performance through superior alertness, concentration, and memory retention (5). Although short naps may have a limited impact on the long-term recovery from a sleep deficit, they can be useful in the short-term in helping students to not only stay alert and productive but also to convert information from short-term to long-term memory (8,13). Furthermore, it is also possible to consume caffeine and then quickly take a brief nap. This method to fight off sleepiness can combine the positive effects of both methods and can be even more beneficial than either approach on its own (13).
References
1. J. B. Maas. Power Sleep. (Random House Inc., New York, 1998).
2. H. Lau, M. A. Tucker, W. Fishbein, Neurobiology of Learning and Memory 93, 554-560 (2010).
3. B. M. Altevogt, H. R. Colten, Eds., Sleep Disorders and Sleep Deprivation: An Unmet Public Health Problem (National Academy of Sciences, Washington D.C., 2006).
4. P. B. Dews, Ed., Caffeine: Perspectives from Recent Research (Springer-Verlag, Berlin, 1984).
5. G. A. Spiller, Ed., Caffeine (CRC Press, New York, 1998).
6. A. B. Ludden, A. R. Wolfson, Health Educ. Behav. 37, 330-332 (2009).
7. B. B. Fredholm, Exp. Cell Res. 316, 1284-1288 (2010).
8. M. Gillberg, G. Kecklund, J. Axelsson, T. Akerstedt, Sleep 19, 570-575 (1996).
9. R. Tremaine et al., Appl. Ergon., 1-10 (2010).
10. M. T. Purness, A. M. Feyer, G. P. Herbison, J. Sleep Res. 11, 219-227 (2002).
11. A. N. Vgontazas et al., Am. J. Physiol. Endorcinol. Metab. 292, E253-E261 (2007).
12. J. Horne, C. Anderson, C. Platten, J. Sleep Res. 17, 432-436 (2008).
13. A. Takashima et al., PNAS 103, 756-761 (2006).
14. L. A. Reyner, J. A. Horne, Psychophysiology 34, 721-725 (1997).