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ORIGINAL ARTICLE
Year : 2020  |  Volume : 27  |  Issue : 1  |  Page : 23-28  

The relationship between sleep quality, stress, and academic performance among medical students


College of Medicine, Imam Mohammad Ibn Saud Islamic University, Riyadh, Saudi Arabia

Date of Submission30-Jun-2019
Date of Decision27-Sep-2019
Date of Acceptance15-Oct-2019
Date of Web Publication13-Jan-2020

Correspondence Address:
Dr. Abdullah D Alotaibi
College of Medicine, Imam Mohammad Ibn Saud Islamic University, Othman Bin Affan Road Al-Nada, P.O. Box 7544, Riyadh 13317-4233
Saudi Arabia
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jfcm.JFCM_132_19

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   Abstract 

BACKGROUND: Sleep is essential for the body, mind, memory, and learning. However, the relationship between sleep quality, stress, and academic performance has not been sufficiently addressed in the literature. The aim of this study was to assess the quality of sleep and psychological stress among medical students and investigate the relationship between sleep quality, stress, and academic performance.
MATERIALS AND METHODS: This cross-sectional study targeted all medical students in their preclinical years at a Saudi medical college in 2019. All students were asked to complete an electronic self-administered questionnaire comprising the Pittsburgh Sleep Quality Index (PSQI), the Kessler Psychological Distress Scale (K10), questions on the students' current overall grade point average, and other demographic and lifestyle factors. The associations between categorical variables were analyzed using Pearson's Chi-squared test at 0.05 significance level.
RESULTS: The mean PSQI score was 8.13 ± 3.46; 77% of the participants reported poor quality of sleep and 63.5% reported some level of psychological stress (mean K10 score: 23.72 ± 8.55). Poor quality of sleep was significantly associated with elevated mental stress levels (P < 0.001) and daytime naps (P = 0.035). Stepwise logistic regression model showed that stress and daytime nap were associated with poor sleep quality. Whereas, poor sleep or stress did not show any significant association with academic performance.
CONCLUSION: Poor sleep quality was significantly associated with elevated levels of strees. However, they did not show any statistically significant relationship with academic performance.

Keywords: Academic performance, medical education, medical students, sleep, sleep quality, stress


How to cite this article:
Alotaibi AD, Alosaimi FM, Alajlan AA, Bin Abdulrahman KA. The relationship between sleep quality, stress, and academic performance among medical students. J Fam Community Med 2020;27:23-8

How to cite this URL:
Alotaibi AD, Alosaimi FM, Alajlan AA, Bin Abdulrahman KA. The relationship between sleep quality, stress, and academic performance among medical students. J Fam Community Med [serial online] 2020 [cited 2020 Jan 18];27:23-8. Available from: http://www.jfcmonline.com/text.asp?2020/27/1/23/275817


   Introduction Top


Sleep, an essential therapeutic part of human physiology, has been well established as critically important for functioning, mental health, and good quality of life.[1] Sleep deprivation has a wide range of harmful effects on human biology and is associated with fatigue, daytime sleepiness, and reduced neurocognitive performance.[2] Cognitive performance in students, including concentration and estimated efforts to complete tasks, is negatively affected by sleep deprivation.[3] The prevalence of poor sleep quality varies between countries. Using the Pittsburgh Sleep Quality Index (PSQI), it has been reported to be as low as 19% in a Chinese study and as high as 55.8% in a study in Ethiopia.[4],[5]

Sleep is vital for the enhancement of working memory capacity and memory consolidation.[6] A meta-analysis of seventy studies concluded that acute sleep deprivation harms most cognitive domains, such as simple attention, intricate attention, working memory, and short-term memory.[7] A prospective study from the 1990s identified prolonged psychological stress in college students who had reported symptoms of insomnia.[8] A delayed circadian rhythm also leads to poor sleep quality, especially during examination periods, and both have been found to negatively affect academic performance.[9],[10] Stress, another factor prevalent among medical students, worsens the quality of sleep.[11] Increased levels of stress have been found to be related to lower academic performance; however, appropriate coping strategies have been shown to help students deal with the negative impact of psychological distress.[12],[13],[14]

Very few studies in Saudi Arabia have addressed the relationship between sleep quality, stress, and academic performance of medical students, and their findings on the impact of sleep on academic performance are variable,[15],[16],[17],[18] although poor sleep quality as high as 76% has been reported.[18] Nevertheless, the majority of Saudi medical students think that the quality of their sleep is good.[18],[19] Multiple local data sources have also suggested high stress levels in medical students.[18],[20],[21] The current study aims to assess sleep quality and psychological stress in medical students in their preclinical years and investigate the relationship between sleep quality, stress, and academic performance.


   Materials and Methods Top


This observational, cross-sectional study was conducted at the College of Medicine at Imam Muhammad Ibn Saud Islamic University (IMSIU), Riyadh, Saudi Arabia, between February and June 2019. The study targeted all medical students in their preclinical phase (1st, 2nd, and 3rd years). In this phase, the college follows an outcome-based, community-oriented, integrated system in which students attend lectures and are engaged in problem-based learning (PBL) small group tutorials. Students are evaluated during and at the end of each body system block.

An electronic self-administered questionnaire was distributed by six well-trained data collectors, two for each academic year. To ensure adequate representation of the study population, the link was restricted to groups of invitees only. A total of 230 participants were required to obtain a 95% confidence level and a 5% margin of error. The link was open from April 7, 2019, to May 7, 2019, and reminders were sent every 3 days.

Ethical approval from the Institutional Review Board of IMSIU was obtained for the study. Participants were informed of the objectives of the study, and informed written consent was obtained from them. They were free to withdraw from the study at any stage; their information was kept confidential and used for research purposes only.

The questionnaire had items on demographic and lifestyle characteristics (age, gender, marital status, work status, residency, academic level, and frequency of caffeine intake and daytime naps) and measures of sleep quality, psychological distress, and academic performance.

Sleep quality was assessed using the global score of the PSQI[22] which starts with four questions on bedtime, sleep latency, wake-up time, and the total hours of actual sleep during the last month. Then, there were 14 questions in a scale form on several suggested factors that troubled sleep such as the utilization of sleep medications, daytime sleepiness, enthusiasm for productivity, and a concluding self-rating question of the overall quality of sleep in the past month. Finally, the global PSQI score was calculated using seven components formed from the content items. The PSQI is considered a cornerstone tool for the measurement of sleep quality.[22],[23]

The Kessler Psychological Distress Scale (K10) was used to investigate the prevalence and levels of stress in medical students. The K10 has ten questions that assessed anxiety and depressive symptoms during the previous month. Items on a 5-point scale had scores ranging from 10 to 50. Scores from 20 to 24 were considered mild distress, 25–29 were moderate, and 30 or higher were severe. The K10 is a popular global tool for assessing nonspecific psychological distress in population-based studies.[24]

Academic performance was measured using the student's current overall grade point average (GPA). Self-reported overall GPA has been frequently used as a measurement of academic achievement in similar studies. Furthermore, high reliability and correlation with GPAs reported by the academic registry had been established.[25],[26] We classified GPA according to the grading system at IMSIU (out of 5.0, the grades 4.5–5.0 are excellent, 3.5–4.49 are very good, and <3.5 are good, pass, or fail).

Data were imported into Microsoft Excel 2016 and analyzed using the Statistical Package for the Social Sciences (SPSS), Version 25.0 (REL. 2017; IBM Corp., Armonk, NY., USA). Categorical variables were presented as frequencies and percentages and continuous variables as means and standard deviations. The associations between categorical variables were analyzed using Pearson's Chi-squared test ± continuity correction. To determine the predictors of poor sleep quality in medical students, a simple logistic regression analysis was initially used to explore the data. Multivariable stepwise binary logistic regression analysis was then performed. The odds ratios (OR) and 95% confidence intervals (95% CI) were calculated, and the Hosmer–Lemeshow test was used to assess model goodness of fit. Statistical significance for all associations was considered to be at P < 0.05.


   Results Top


The characteristics of the study participants are presented in [Table 1]. The total number of participants was 282; 64.5% were male, 61% were aged 21–24 years, and 36.5% were aged 18–21 years. The majority of students were single (n = 276, 97.9%), did not have a job (n = 223, 79.1%), and were living with their families (n = 269, 95.4%). For the academic level, 39% of the respondents were in their 1st year, 25.9% in their 2nd year, and 35.1% in their 3rd year. Most students were rated very good (32.6%; GPA: 3.5–4.49) or excellent (33%; GPA: 4.5–5.0) in their academic performance; about one-third were good or below (34.4%; GPA: <3.5). Assessed dietary habits included frequency of caffeine consumption; 61.7% of the respondents consumed caffeine daily, 18.8% consumed it weekly (2–5 times per week), and 19.5% consumed every 2 weeks or less.
Table 1: Characteristics of medical students in preclinical years (n=282)

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The prevalence of poor sleep quality of the participants was 77% (n = 217, mean PSQI score: 8.13 ± 3.46). The period from 00:00 to 1:59 was the most frequent for bedtime (n = 145, 51.4%) followed by the period from 2:00 to 3:59 (n = 73, 25.9%); only 19.1% had a usual bedtime before midnight. The average total hours of sleep were 5.87 ± 1.56 per night. However, >43% reported having a daytime nap. The overall total hours of actual sleep ranged from 2 to 12.

Distress was also prevalent: 63.5% of the students exhibited positive distress on the K10 (n = 179). More than 41% of the respondents had either a moderate or severe level of distress, and approximately one-fourth had a severe level of distress. Mild and moderate levels were 22% and 17.4%, respectively. The K10 scores covered the entire possible range, from 10 to 50, with a mean score of 23.72 ± 8.55.

[Table 2] presents the associations of poor sleep quality and stress with GPA, work status, and other variables in the study. A greater proportion of participants who had poor sleep quality reported distress compared to participants who did not have poor sleep quality (68.7% and 46.2%, respectively; P = 0.002). The prevalence of poor sleep quality also increased with each distress level: 67.7% for mild distress, 87.8% for moderate distress, and 94.1% for severe distress (P < 0.001). Taking a daytime nap showed a statistically significant association with poor sleep quality, with 81.9% of the participants who took daytime naps reporting poor sleep quality compared to only 70.5% of the participants who did not take naps (P = 0.035).
Table 2: Characteristics of the medical students in their preclinical years by sleep quality and stress (n=282)

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In contrast, poor sleep quality was nearly the same between the genders and academic levels. Similarly, there was no difference in the distress suffered by students who took daytime naps and those who did not or between students who worked and those who did not. Students' current overall GPAs also did not show significant associations with poor sleep quality or distress level.

The multivariable stepwise binary logistic regression analysis to predict poor sleep quality in the participants is shown in [Table 3]. High levels of distress were highly associated with poor sleep quality. For instance, normal (OR = 0.108, 95% CI: 0.036–0.325) and mild (OR = 0.112, 95% CI: 0.035–0.358) distress showed significant negative associations with poor sleep, but there was no significant difference between the moderate distress level and the high distress level, which was used as a reference (OR = 0.383, 95% CI: 0.101–1.458, P = 0.159). Compared to students who took daytime naps, those who did not nap had only 0.453 times the odds of reporting poor sleep quality (95% CI: 0.250–0.821, P = 0.009).
Table 3: Correlates of poor sleep quality among the medical students in their preclinical years

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   Discussion Top


In the present study, 77% of the participants had a poor quality of sleep. This result is similar to other studies in Saudi Arabia (76% and 74.2%).[18],[27] However, a study from the Southern region of Saudi Arabia had a different result (29.7%).[28] Internationally, the quality of sleep of medical students has generally been found to be better: 50.9% in the United States,[29] 55.8% in Ethiopia,[5] 19% in China, and 40% in Lithuania.[4] The prevalence of stress in participants in the current study was 63.5%, which is also higher than similar local and international studies. For instance, a prevalence of about 53% was found in two colleges in Riyadh[18],[20] and 41.9% in Malaysia.[30]

Examination periods increase both stress and poor sleep quality of medical students.[10],[31] Ahrberg et al. found that the quality of sleep of students in the 5 weeks preceding examinations was significantly worse than in the semester or 4 weeks afterward.[10] This could be an explanation for the high prevalence of poor sleep quality in the present study, since students were enrolled in a 3–6-week block systems in which they were assessed by weekly PBL sessions, mid-block and final examinations, and tutorial and seminar assessments.

Poor sleep quality was significantly associated with the level of stress in medical students in this study (P < 0.001). This association has been widely reported.[10],[14],[31] Morin et al. found that participants who had symptoms of insomnia were more stressed than noninsomniacs.[14] They also concluded that there was either a direct or indirect relationship between insomnia and stress, nighttime arousal, and emotional responses to stress. Notably, stress was more prevalent in female students in this study (P < 0.001), but no significant association between gender and sleep quality was found.

In spite of the expected start of the first lecture of the day (8:00 am), the majority of students (80.8%) reported that they had gone to bed at midnight or later. Similarly delayed bedtime was found in other local universities (12:06 am ± 1.58; 1:53 am ± 3:51; and 77.2% at midnight or later).[15],[18],[19] In a study from Thailand, 54% of the students reported a bedtime between 10.00 pm and 12.00 am, but during examination periods, 41% of the students would go to bed between 2:00 am and 4:00 am.[32]

Taking a daytime nap not only increases afternoon alertness but also negatively affects sleep quality in young adults.[33],[34] However, in our study, daytime naps showed a significant association with, and were predictive of, poor sleep quality. This suggests that napping by participants in this study was more likely to be compensated for insufficient nighttime sleep than planned, and habitual compensatory daytime naps are frequently used to cope with altered circadian rhythms.[9]

The negative impact of poor sleep quality and stress on academic performance has been well reported in the literature.[9],[10],[12] However, surprisingly, in this study, academic performance showed no statistically significant association with sleep quality or stress levels. This result is similar to data reported by Alqarni et al., Al-Zahrani et al., and Abdulghani et al.[16],[17],[21] Conversely, some local studies have concluded that sleep disorders negatively affect academic performance.[15],[35] This inconsistency in local studies may draw attention to the new trends in sleep–wake habits and their relationship to the professional life of young adults in Saudi Arabia. This point, as well as the cultural aspects (sleep–wake patterns in hot countries), should be taken into consideration in future studies.

This study was based in a single institution, so the specific environment of that institution may have had an impact on the accuracy of the generalizability of the results. The cross-sectional design, which collected responses at a single point in time, could not provide a causal relationship between variables. Furthermore, since students were asked about their sleep quality and stress in the previous month, there could have been recall bias. We recommend that future studies continue to investigate different psychological and behavioral parameters of medical students and their impact on academic performance and assess the role of different medical pedagogies and ways of assessment in that relationship. In the meantime, sleep quality and levels of stress in medical students could be improved with campaigns on sleep education, counseling on time management, and plans for treatment.[36],[37],[38]


   Conclusion Top


This study showed that the quality of sleep in medical students in their preclinical years was poor and their stress levels elevated, with these two variables significantly associated. Furthermore, stress and daytime naps were significant predictors of poor sleep quality. Stress was more prevalent among females. Surprisingly, academic performance did not show any statistically significant association with sleep quality or stress levels. Researchers and medical educationists are encouraged to continue to assess students' well-being, methods of education, and factors that affect academic performance and in the meantime improve students' sleep quality through counseling and educational campaigns.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
   References Top

1.
Altevogt BM, Colten HR. Sleep Disorders and Sleep Deprivation: An Unmet Public Health Problem. Washington, D.C.: National Academies Press; 2006.  Back to cited text no. 1
    
2.
Aldabal L, Bahammam AS. Metabolic, endocrine, and immune consequences of sleep deprivation. Open Respir Med J 2011;5:31-43.  Back to cited text no. 2
    
3.
Pilcher JJ, Walters AS. How sleep deprivation affects psychological variables related to college students' cognitive performance. J Am Coll Health 1997;46:121-6.  Back to cited text no. 3
    
4.
Azad MC, Fraser K, Rumana N, Abdullah AF, Shahana N, Hanly PJ, et al. Sleep disturbances among medical students: A global perspective. J Clin Sleep Med 2015;11:69-74.  Back to cited text no. 4
    
5.
Lemma S, Gelaye B, Berhane Y, Worku A, Williams MA. Sleep quality and its psychological correlates among university students in Ethiopia: A cross-sectional study. BMC Psychiatry 2012;12:237.  Back to cited text no. 5
    
6.
Fenn KM, Hambrick DZ. Individual differences in working memory capacity predict sleep-dependent memory consolidation. J Exp Psychol Gen 2012;141:404-10.  Back to cited text no. 6
    
7.
Lim J, Dinges DF. A meta-analysis of the impact of short-term sleep deprivation on cognitive variables. Psychol Bull 2010;136:375-89.  Back to cited text no. 7
    
8.
Chang PP, Ford DE, Mead LA, Cooper-Patrick L, Klag MJ. Insomnia in young men and subsequent depression. The Johns Hopkins precursors study. Am J Epidemiol 1997;146:105-14.  Back to cited text no. 8
    
9.
Phillips AJ, Clerx WM, O'Brien CS, Sano A, Barger LK, Picard RW, et al. Irregular sleep/wake patterns are associated with poorer academic performance and delayed circadian and sleep/wake timing. Sci Rep 2017;7:3216.  Back to cited text no. 9
    
10.
Ahrberg K, Dresler M, Niedermaier S, Steiger A, Genzel L. The interaction between sleep quality and academic performance. J Psychiatr Res 2012;46:1618-22.  Back to cited text no. 10
    
11.
Škerstedt T, Orsini N, Petersen H, Axelsson J, Lekander M, Kecklund G. Predicting sleep quality from stress and prior sleep – A study of day-to-day covariation across six weeks. Sleep Med 2012;13:674-9.  Back to cited text no. 11
    
12.
Stewart SM, Lam TH, Betson CL, Wong CM, Wong AM. A prospective analysis of stress and academic performance in the first two years of medical school. Med Educ 1999;33:243-50.  Back to cited text no. 12
    
13.
Sohail N. Stress and academic performance among medical students. J Coll Physicians Surg Pak 2013;23:67-71.  Back to cited text no. 13
    
14.
Morin CM, Rodrigue S, Ivers H. Role of stress, arousal, and coping skills in primary insomnia. Psychosom Med 2003;65:259-67.  Back to cited text no. 14
    
15.
Bahammam AS, Alaseem AM, Alzakri AA, Almeneessier AS, Sharif MM. The relationship between sleep and wake habits and academic performance in medical students: A cross-sectional study. BMC Med Educ 2012;12:61.  Back to cited text no. 15
    
16.
Al-Zahrani JM, Aldossari KK, Abdulmajeed I, Al-Ghamdi SH, Al-Shamrani AM, Al-Qahtani NS. Daytime sleepiness and academic performance among medical students. Health Sci J 2016;10:1-5.  Back to cited text no. 16
    
17.
Alqarni AB, Alzahrani NJ, Alsofyani MA. The interaction between sleep quality and academic performance among the medical students in Taif university. Egypt J Hosp Med 2018;70:2202-8.  Back to cited text no. 17
    
18.
Almojali AI, Almalki SA, Alothman AS, Masuadi EM, Alaqeel MK. The prevalence and association of stress with sleep quality among medical students. J Epidemiol Glob Health 2017;7:169-74.  Back to cited text no. 18
    
19.
Alsaggaf MA, Wali SO, Merdad RA, Merdad LA. Sleep quantity, quality, and insomnia symptoms of medical students during clinical years. Relationship with stress and academic performance. Saudi Med J 2016;37:173-82.  Back to cited text no. 19
    
20.
Abdel Rahman AG, Al Hashim BN, Al Hiji NK, Al-Abbad Z. Stress among medical Saudi students at college of medicine, King Faisal university. J Prev Med Hyg 2013;54:195-9.  Back to cited text no. 20
    
21.
Abdulghani HM, AlKanhal AA, Mahmoud ES, Ponnamperuma GG, Alfaris EA. Stress and its effects on medical students: A cross-sectional study at a college of medicine in Saudi Arabia. J Health Popul Nutr 2011;29:516-22.  Back to cited text no. 21
    
22.
Buysse DJ, Reynolds CF 3rd, Monk TH, Berman SR, Kupfer DJ. The Pittsburgh sleep quality index: A new instrument for psychiatric practice and research. Psychiatry Res 1989;28:193-213.  Back to cited text no. 22
    
23.
Backhaus J, Junghanns K, Broocks A, Riemann D, Hohagen F. Test-retest reliability and validity of the pittsburgh sleep quality index in primary insomnia. J Psychosom Res 2002;53:737-40.  Back to cited text no. 23
    
24.
Kessler RC, Andrews G, Colpe LJ, Hiripi E, Mroczek DK, Normand SL, et al. Short screening scales to monitor population prevalences and trends in non-specific psychological distress. Psychol Med 2002;32:959-76.  Back to cited text no. 24
    
25.
Bacon DR, Bean B. GPA in research studies: An invaluable but neglected opportunity. J Mark Educ 2006;28:35-42.  Back to cited text no. 25
    
26.
Cassady JC. Self-reported GPA and SAT: A methodological note. Pract Assess Res Eval 2001;7:1-6.  Back to cited text no. 26
    
27.
Siddiqui AF, Al-Musa H, Al-Amri H, Al-Qahtani A, Al-Shahrani M, Al-Qahtani M. Sleep patterns and predictors of poor sleep quality among medical students in King Khalid university, Saudi Arabia. Malays J Med Sci 2016;23:94-102.  Back to cited text no. 27
    
28.
Asiri AK, Almetrek MA, Alsamghan AS, Mustafa O, Alshehri SF. Impact of twitter and whatsapp on sleep quality among medical students in king Khalid university, Saudi Arabia. Sleep Hypn Int J 2018;20:247-52.  Back to cited text no. 28
    
29.
Brick CA, Seely DL, Palermo TM. Association between sleep hygiene and sleep quality in medical students. Behav Sleep Med 2010;8:113-21.  Back to cited text no. 29
    
30.
Sherina MS, Rampal L, Kaneson N. Psychological stress among undergraduate medical students. Med J Malaysia 2004;59:207-11.  Back to cited text no. 30
    
31.
Zunhammer M, Eichhammer P, Busch V. Sleep quality during exam stress: The role of alcohol, caffeine and nicotine. PLoS One 2014;9:e109490.  Back to cited text no. 31
    
32.
Sitticharoon C, Srisuma S, Kanavitoon S, Summachiwakij S. Exploratory study of factors related to educational scores of first preclinical year medical students. Adv Physiol Educ 2014;38:25-33.  Back to cited text no. 32
    
33.
Gillberg M, Kecklund G, Axelsson J, Akerstedt T. The effects of a short daytime nap after restricted night sleep. Sleep 1996;19:570-5.  Back to cited text no. 33
    
34.
Pilcher JJ, Michalowski KR, Carrigan RD. The prevalence of daytime napping and its relationship to night time sleep. Behav Med 2001;27:71-6.  Back to cited text no. 34
    
35.
Abdulghani HM, Alrowais NA, Bin-Saad NS, Al-Subaie NM, Haji AM, Alhaqwi AI. Sleep disorder among medical students: Relationship to their academic performance. Med Teach 2012;34 Suppl 1:S37-41.  Back to cited text no. 35
    
36.
Orzech KM, Salafsky DB, Hamilton LA. The state of sleep among college students at a large public university. J Am Coll Health 2011;59:612-9.  Back to cited text no. 36
    
37.
Brown FC, Buboltz WC Jr., Soper B. Development and evaluation of the sleep treatment and education program for students (STEPS). J Am Coll Health 2006;54:231-7.  Back to cited text no. 37
    
38.
Macan TH, Shahani C, Dipboye RL, Phillips AP. College students' time management: Correlations with academic performance and stress. J Educ Psychol 1990;82:760.  Back to cited text no. 38
    



 
 
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