Sleep-wake patterns and academic performance in university students
Gomes, Ana Allen (1); Tavares, José (1); Azevedo, Maria Helena
(1) Dep. Sciences of Education, University of Aveiro. Portugal. E-mail: email@example.com
(2) Sleep Disorders Unit - H.U.C.; Fac. of Medicine, University of Coimbra. Portugal.
Paper presented at the European Conference on Educational Research, University of Lisbon, 11-14 September 2002.
Apparently, the relationships between sleep, circadian rhythms, and academic performance, in students, have received little attention by practitioners and researchers in the field of education. The aim of this work was to perform a literature review about this issue in university students. A computer search and published literature consultation, to locate relevant articles, were conducted. Although vast literature reports associations between sleep and performance, articles specifically interested on academic performance were sparse. Despite the reduced number of studies, the findings suggest that several sleep dimensions, as sleep-wake schedules, and individual circadian rhythms characteristics, may be associated to the academic results achieved by university students. Given the reduced number of studies found, further research is needed. Since sleep-wake patterns may have important implications over daytime functioning, we are undertaking the first Portuguese study with university students in this specific research issue.
Sleep and wakefulness are intimately related states, with mutual influences (Ramos Platón, 1996). The present work focuses on the effects of sleep over wakefulness. Regarding the question about sleep functions, or why do we sleep, there is still not a definitive answer. Among others, sleep is important for cognitive restitution. It influences information processing, learning and memory consolidation (e.g., Lavie, 1996; Li Deming et al., 1991; Ramos Pláton, 1996). Therefore a certain amount of sleep is needed to adequate wakefulness. Sleep deprivation seems to impair particularly cognitive functions related to the prefrontal cortex, such as flexible and divergent thinking; dealing with novelty and unexpected; verbal fluency; novel responses and suppression of routine answers (Horne, 2000).
Besides the amount (or hours of sleep), the timing is also vital for adequate daytime functioning. The sleep-wake cycle is a circadian rhythm, which is spontaneously generated by the organism, with a periodicity, in the adult, of about 1 day (cf., e.g., Minors & Waterhouse, 1981). Therefore, we tend to maintain relatively stable schedules. Since the sleep-wake cycle is in harmony with other inner circadian rhythms, for example, deep body temperature and cellular mitoses, therefore, abrupt shifts of sleep-wake schedules lead to internal dissociation among circadian rhythms, which may imply undesirable effects such as somnolence, attention deficits, concentration difficulties, and performance decrements, which is very common in shift work and rapid travels across multiple time zones (DCSC, 1990). Some studies in undergraduates indicated that irregularities of 2-4 hours in the sleep-wake schedules are associated with higher fatigue, deterioration of mood and performance (Taub and Berger, 1973, 1974), and that students with irregular sleep-wake schedules had excessive daytime somnolence, comparing to regular colleagues (Manber et al., 1996).
As for other human characteristics, there are normal variations in the sleep-wake patterns and circadian rhythm characteristics (cf., e.g., Buela-Casal & Caballo, 1990; Kerkhoff, 1985). With respect to sleep duration, the majority of the population needs to sleep about 8 hours to fell well during the day. However, some people need more than 9 hours, the called long sleepers, and others feel well with less than 6 hours of sleep, the short sleepers. There are also inter-individual differences in the timing of the sleep-wake cycle, which have to do with the circadian rhythms. At the one hand, there are morning type people, that tend to be somnolent during the evening, enjoys going to bed and to wake up very early; they feel at their best in the morning (work, mood), and become increasingly tired across the day. At the other hand, evening type people like to go to bed and to wake up late, when possible; they do no functioning well during the morning, become increasingly alert across the day and feel at their best in the afternoon or at the evening. They have much higher tolerance to night work than other persons. The majority of people are intermediate type. Unfortunately, work and school schedules do not consider these inter-individual differences. In particular, school schedules are not usually adjusted to eveningness preferences.
In what concerns the sleep-wake patterns of the university student, the entrance at the university is accompanied by many factors that may lead to changes in sleep habits, such as academic demands, new social opportunities, change in sleeping circumstances, diminution of parental guidance, erratic school schedules, part-time jobs (Carskadon & Davis, 1989), and increase night life (for instance, during academic festivities). It is then understandable that, across the university years, many students may develop inadequate sleep patterns. Some sleep-wake difficulties most likely to be found in university students are: later sleep-wake schedules (e.g., Carskadon & Davis, 1989), or even the development of delayed sleep-phase difficulties (Lack, 1986); irregular sleep-wake schedules (e.g., Manber et al., 1996; Medeiros et al., 2001), which indicates inadequate sleep hygiene; insufficient sleep duration (Hicks et al., 1989; Hicks & Pellegrini, 1991); insomnia complaints (Giesecke, 1987). As indicated by the International Classification of Sleep Disorders (DCSC, 1990), such sleep-wake patterns are usually accompanied by undesirable daytime consequences: decrease levels of motivation, performance, concentration, attention, and humour, as well as increase fatigue and somnolence. Thus, it is reasonable to suppose that those university students that develop such sleep patterns may suffer consequences over their academic performance. However, literature about this subject among university students seems scarce.
In general, despite the demonstrations about the important role of sleep for wakefulness, the study of the associations between sleep habits of students, circadian rhythms characteristics and academic performance, assessed in natural educational conditions, has received little attention in the field of education. The aim of the present work was to perform a literature review about the relationship between sleep-wake patterns (and/or circadian rhythm characteristics) and academic performance in university students.
Firstly, a computer-assisted literature search of the databases ERIC and MEDLINE (1966-2002) was conducted. The Boolean operator and was used for combining the following key words: 1-college / university student; 2-sleep / circadian rhythm / diurnal type; 3-academic performance / school performance / academic achievement / school achievement / school failure / grade point average. The publication types selected were articles in scientific journals. Secondly, the abstracts retrieved were scrutinised in order to identify the relevant articles. Thirdly, the articles selected were further important sources to locate other studies. We also consulted published literature, books and papers, as well as respective bibliographic references sections, to locate other relevant journal articles. In a less systematic way, we consulted other databases, as Current Contents (1997- 2002) and BiblioSleepResearch (1990-2000).
We were able to locate a total of 17 journal articles reporting results about the associations of academic functioning with sleep-wake variables, in university students. It should be mentioned that not all of these studies addressed the relationship between sleep/circadian rhythms and academic performance as a main aim; some of them dealt with the subject only in part; others had clearly different scopes, but, even dough, they were selected because they reported findings of interest for our aims.
Among the articles selected, 9 studies considered academic outcomes, i.e., university grades (e.g., results in testes or exams, grade point averages), and were non-experimental studies. The most consistent findings were that lower academic results were associated with less sleep duration (Jean-Louis et al., Medeiros et al., 2001; 1996; Trockel et al., 2000), with later bedtimes / sleep onset (Medeiros et al., 2001; 1996; Smith et al., 1989; Trockel et al., 2000) and with later rise times / awakening times (Johns et al., 1976; Smith et al., 1989; Trockel et al., 2000). Similarly, lower academic results were associated with eveningness orientation (Medeiros et al., 2001; Smith et al., 1989). Congruent with these results, students with delayed sleep-phase problems, which imply later sleep-wake schedules, obtained lower mean grades than their colleagues (Lack, 1986). On a study assessing personality traits, Conscientiousness (especially its facet of Achievement Striving) was a significant predictor of academic performance and conscious individuals maintained earlier schedules (Gray & Watson, 2002). As isolated results, lower academic grades were also found to be associated to other sleep variables as irregular sleep-wake cycle (Medeiros et al., 2001), longer sleep latency, falling asleep in school (Jean-Louis et al., 1996), poor sleep quality (Johns et al., 1976), and excessive daytime sleepiness (Rodrigues et al., 2002). Among these 9 studies review so far, 1 found no significant relationships between any aspect of sleep and academic performance (Shapiro et al. 1980).
Two articles about time of the day and academic (or related) performance were found. One of them was an interesting study about instructional and examination schedules, which ran on a small liberal arts college, were, contrarily to the usual, students had opportunity to choose their schedules. Mean grades of students attending morning classes were significantly lower than those of the students attending afternoon and evening classes, that probably had later sleep-wake schedules than students in the morning classes (Skinner, 1985). On the other study about time of the day, students participated in a long-term memory test (speed of accessing information from long-term memory) at three times of the day: in the morning, in the afternoon, and in the evening. Throughout the day, performance of morning-type students decreased, whereas performance of evening types improved (Anderson et al., 1991). The results suggested that cognitive performance over the day depends on the interaction between hour of the day and diurnal type of the individual.
Among the articles selected, two were controlled studies (manipulating variables) about the influence of sleep deprivation over performance in academic-related tasks. One of them found that sleep deprivation in medical students (4 hours or less of uninterrupted sleep per night while participating in scheduled in-house night call) did not influence short-term and long term retention of newly learned medical material (Browne et al., 1994). On the interesting study by Pilcher and Walters (1997), sleep deprived students (1 night of sleep-loss), comparing to a non-deprived control group (8 hrs sleep), performed significantly worse in a cognitive task (Watson-Glaser Critical Thinking Appraisal) but, surprisingly, they rated their estimated performance significantly higher than the non-deprived colleagues. The authors concluded that university students might not be aware of the extent to which sleep deprivation may negatively affects their ability to complete cognitive tasks.
We found one study about snoring in medical students. Results indicated that frequent snoring students may obtain worse examination scores than their colleagues, and they are at a higher risk of failing exams (Ficker et al., 1990). These may be due to fragmentation of sleep due to snoring, which undermines sleep quantity and quality. However, Medeiros et al. (2001) did not found significant relationship between snoring and academic performance.
We also selected 3 studies about the associations of sleep with other aspects of academic functioning, two of them about anxiety related with academic tasks: students with the highest anxiety about learning foreign languages tended to report insufficient amount of sleep (Bailey et al., 2000); short sleepers had significantly higher levels of test anxiety, than long sleepers (Hicks et al., 1979). The third study found that eveningness significantly predicted academic procrastination, and neuroticism partially mediated that relationship (Hess et al., 2001).
The associations between insufficient sleep duration and lower university grades are understandable in the view of sleep functions. Such findings agree with the supposition that, during sleep, learning and memory consolidation occur (cf. "Introduction").
Consistent findings were the associations of poorer academic performance with later sleep-wake schedules and/or with eveningness orientation. These findings are not so easy to interpret. Why do students with later sleep-wake patterns and/or preferences may obtain lower results? There are several possibilities: 1 - They miss morning classes in order to obtain enough sleep. 2 - They wake up early to attend morning classes and, in this case, they are still at disadvantage: (a) they must attend classes and examinations on the morning, when they are not yet at their best, i.e., time of the day incongruent with their individual circadian rhythm characteristics (cf. Anderson et al., 1991); (b) they become sleep deprived (because probably they went to bed late the previous night), and (c) sleep-wake schedules become irregular, for example, because they wake up late on weekends. As mentioned in "Introduction", either sleep deprivation or irregular sleep-wake schedules may undermine adequate daytime functioning. We therefore propose that, whenever morning schedules are imposed for instruction and examinations, it is reasonable to expect that evening types and students with later sleep-wake patterns may have worse academic performance. In fact, based on Skinner (1985) results we may suppose that late sleep-wake patterns are not a problem if the student had the opportunity to attend afternoon or evening instructional schedules.
As concluding remarks, although the findings of the studies reviewed did not prove causal relationships, they strongly suggest that academic functioning of university students is (at least in part) associated with sleep and wake patterns. Research about this subject is still reduced, but results seem promising, thus, further studies are needed. We are now undertaking the first Portuguese research about the subject in university students. According to Medeiros et al. (2001), exogenous (e.g., school schedules; academic demands) and endogenous (e.g., chronotype) factors may influence the sleep-wake cycle of the university student; inadequate sleep-wake patterns (e.g., irregular; insufficient sleep) may in turn influence academic performance.
Based on the findings from the literature reviewed, we believe that the knowledge about sleep-wake patterns and circadian rhythms may be important for a better understanding of the academic failure/success at the university, and may be used to improve intervention processes to achieve greater success at the university. For example, information about adequate sleep-wake habits may help student to achieve a more efficient learning, with less wastes of time, effort, energy and motivation; assessment of circadian rhythm characteristics may be useful for counselling students as how to cope best with instructional and examination schedules, by taking account of each student individual characteristics.
This study was supported by UI-CCPSF and Project LEIES / F. C. Gulbenkian.
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