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Volume 13 No. 10
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Scientific Investigations

Sleep Duration and Sleep Patterns in Chinese University Students: A Comprehensive Meta-Analysis

Lu Li, MSc1,2; Yuan-Yuan Wang, PhD1; Shi-Bin Wang, PhD3; Lin Li, MSc4,5; Li Lu, MSc1; Chee H. Ng, MBBS, MD6; Gabor S. Ungvari, MD, PhD7; Helen F.K. Chiu, FRCPsych8; Cai-Lan Hou, MD, PhD3; Fu-Jun Jia, MD3; Yu-Tao Xiang, MD, PhD1
1Unit of Psychiatry, Faculty of Health Sciences, University of Macau, Macao SAR, China; 2The Affiliated Brain Hospital of Guangzhou Medical University (Guangzhou Huiai Hospital), Guangzhou, China; 3Guangdong Mental Health Center, Guangdong General Hospital and Guangdong Academy of Medical Sciences, Guangdong Province, China; 4Faculty of Life Sciences and Biopharmaceutics, University of Shenyang Pharmaceutical, Shenyang, China; 5Liaoning Medical Device Test Institute, Shenyang, China; 6Department of Psychiatry, University of Melbourne, Melbourne, Victoria, Australia; 7Graylands Hospital, Perth, Australia; 8Department of Psychiatry, Chinese University of Hong Kong, Hong Kong SAR, China

ABSTRACT

Study Objectives:

This meta-analysis aimed to determine duration and patterns of sleep in Chinese university students.

Methods:

English (PubMed, PsycINFO, Embase) and Chinese (SinoMed, Wan Fang Database, and Chinese National Knowledge Infrastructure) databases were systematically and independently searched from their inception until August 16, 2016. Data on sleep duration and sleep patterns of tertiary student population in eligible studies were extracted and pooled using random-effects models.

Results:

A total of 57 studies with 82,055 university students were included in the meta-analysis. Pooled mean sleep duration was 7.08 h/d (95% confidence interval [CI]: 6.84 to 7.32 h/d). The percentage of students with sleep duration shorter than 6 h/d and 7 h/d (short sleep) was 8.4% (95% CI: 5.7% to 12.3%) and 43.9% (95% CI: 36.9% to 51.1%), respectively. In contrast, the percentage of students with sleep duration longer than 8 hours and 9 hours (long sleep) was 18.3% and 5.7%, respectively. The pooled mean bedtime was at 12:51 am. The percentage of university students who fall asleep after midnight was 23.8%. The percentage of students with sleep latency more than 30 minutes was 25.5%. The pooled mean wake-up time was at 8:04 am on weekdays and on weekends.

Conclusions:

Short sleep duration and unhealthy sleep patterns were found to be common among Chinese university students.

Citation:

Li L, Wang YY, Wang SB, Li L, Lu L, Ng CH, Ungvari GS, Chiu HF, Hou CL, Jia FJ, Xiang YT. Sleep duration and sleep patterns in chinese university students: a comprehensive meta-analysis. J Clin Sleep Med. 2017;13(10):1153–1162.


INTRODUCTION

The use of smartphone and electronic reading devices prior to bedtime is becoming more common, resulting in changing sleep patterns.13 In the past 50 years there was a decline in sleep duration by 1.5 to 2 hours in the United States.4 Sleep time is shortened and bedtime is typically delayed in adolescence,5 a finding also noted in university students. Apart from the effect of new media, other factors including the lack of parental supervision, changed living environment on campus, caffeine or energy drinks, and academic stress may contribute to irregular sleep habits in university students.58 Over the past decades, the prevalence of dissatisfaction with sleep quality among university students has increased.9

Irregular sleep habits and other sleep problems in university students are a global issue. For instance, 36.2% of Palestinian university students have a sleep latency of more than 30 minutes and 41.7% go to bed after midnight.10 In the United States, students go to bed at 12:17 AM and wake up at 8:02 AM on weekdays, but mean bedtimes (1:44 AM) and wake-up time (10:08 AM) are delayed on weekends.7 In China irregular sleep habits, delayed bedtime, early wake-up, and sleep deprivation are also common in university students. According to the report of the Ministry of Education in 2015, there were approximately 37 million university students in China accounting for approximately one-fifth of university students globally. University students have to cope with multiple pressures, including a shrinking job market, that increase the risk of irregular sleep patterns. Socio-demographic and cultural factors play important roles in sleep-related disturbances including irregular sleep habits1114; therefore, findings obtained in a particular sociocultural context, in Western or Middle-Eastern countries, can hardly be generalized to other countries such as China.15

BRIEF SUMMARY

Current Knowledge/Study Rationale: Short and long sleep duration and sleep patterns are usually associated with poor health outcomes. The results of patterns of sleep duration in Chinese university students have been inconsistent.

Study Impact: Short sleep duration and unhealthy sleep patterns were common in Chinese university students. Given their negative effect on health, quality of life, and intellectual performance, educational and health professionals should pay more attention to sleep patterns in this population.

Irregular sleep-wake patterns and poor sleep quality are associated not only with increased tiredness but also with significant effects on endocrinology, immunology, and metabolism status.16,17 Sleep-deprived students usually perform significantly worse than those with normal sleep.18,19 In addition, short sleep duration is associated with unhealthy risk behaviors, such as alcohol and tobacco use, which could increase the risk for developing hypertension, obesity, diabetes, hypercholesterolemia, and even mortality.2025 In contrast, long sleep duration can also be associated with negative outcome, such as increased risk of cardiovascular disease and cognitive impairment.2628

To date there has been no gold standard criteria for short and long sleep duration. Epidemiological studies usually defined self-reported short and long sleep duration as less than 6 or 7 hours per day and more than 8 or 9 hours per day, respectively.26,2931 Some researchers suggested 7 to 8 hours per day as appropriate for the university students, whereas fewer than 7 hours is defined as short sleep and more than 8 hours is regarded as long sleep.32,33 The National Sleep Foundation has recommended 7 to 9 hours per day as the appropriate sleep duration for young adults.34

To date a number of studies have examined sleep duration and patterns in university students, but the results have been inconsistent. There has not been any meta-analysis of the pooled data on sleep duration and patterns in this population, which is the rationale for conducting this study.

METHODS

Search Strategies

Both English (PubMed, EMBASE and PsycINFO) and Chinese (SinoMed, WanFang, and Chinese National Knowledge Infrastructure [CNKI]) databases were systematically and independently searched by two reviewers from inception until August 16, 2016. The following search terms were used, including (“China” or “Chinese”) and (“insomnia” or “sleep symptoms” or “sleep disorders” or “sleep quality” or “sleep disturbance” or “sleep problem” or “sleep time” or “sleep duration” or “sleep habit” or “sleep pattern”) and (“prevalence” or “epidemiology survey” or “cross-sectional study”) and (“university students” or “college students” or “undergraduate students” or “adolescents” or “young adults”). We also searched the reference lists of the selected articles to find additional records.

Study Selection

We included original quantitative studies that satisfied the following criteria: (1) cross-sectional epidemiological studies conducted in university students in mainland China, Hong Kong, Macao, and Taiwan; and (2) available data on self-reported nocturnal sleep time (mean and standard deviation, proportion of short and long sleep duration, or sleep pattern (bedtime, wake-up time, afternoon nap, and sleep latency). Exclusion criteria were: (1) case studies, (2) surveys without sampling method, and (3) specific populations (eg, patients in hospitals, or those having physical or psychiatric problems). Two reviewers (LL and YYW) checked the title, abstract, and full text of the initial search results independently, and any discrepancies uncovered during these procedures were checked and resolved by a third reviewer (SBW).

Quality Evaluation

Two reviewers (LL and YYW) assessed the methodological quality of the included studies using the 22-item Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) instrument that assesses the title, abstract, introduction, methods, results, and discussion sections of included studies.35 Disagreements were resolved by discussion between the two reviewers, and a third reviewer (SBW) was referred if needed. Studies with a score of 11 or less were classified as “poor quality.”36 Otherwise, they were rated as “good quality.”

Data Extraction

Data were independently extracted by two reviewers (LL and YYW), and were checked by a third reviewer (SBW). The following information was extracted and tabulated: sampling and recruitment methods, study time, characteristics of the participants, study location, and sleep-relevant information.

Statistical Analyses

The Stata software version 12.0 (Stata Corporation, College Station, Texas, United States) and the Comprehensive Meta-Analysis software version 2 (Biostat Inc., Englewood, New Jersey, United States) were used to perform the meta-analysis. The outcome measures of the individual studies were combined using a random-effects model, and standardized mean difference with 95% confidence intervals (CI) was used for data synthesis. I2 statistic was used to evaluate heterogeneity of the studies, with I2 values greater than 50% indicating heterogeneity.37 The visual funnel plot, Egger test, and Begg test were used to assess possible publication bias.38 The “trim and fill” method was used to estimate the number of potential missing studies using a random-effects model. Sensitivity analysis was conducted by excluding each study individually to evaluate the quality and consistency of the results. All analyses were two tailed, with alpha set at .05.

RESULTS

Search Results, Studies Characteristics, and Quality Assessment

Figure 1 presents the flow chart of the search and selection process. A total of 3,112 records were collected during the initial search. After removing the duplicates, 2,239 were screened by title and abstract. After full-text review of the remaining 434 studies, 377 studies were excluded. Finally, 57 studies (10 studies in English and 47 studies in Chinese) with 82,055 university students were included for analyses. Table 1 shows the basic characteristics of the studies, in which 18 reported the mean sleep duration and 41 reported the prevalence of short and/or long sleep. The mean STROBE score of the included studies was 15, ranging from 11 to 20. Five studies (8.8%) were rated as “poor quality,” and the rest were “good quality.”

Flowchart for the selection of studies.

CNKI = Chinese National Knowledge Infrastructure.

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Figure 1

Flowchart for the selection of studies.

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Characteristics of studies included in the meta-analysis.

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Table 1

Characteristics of studies included in the meta-analysis.

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Sleep Duration

The pooled sleep duration in 18 studies with available data was 7.08 h/d (95% CI: 6.84–7.32 h/d) (Figure 2). Table S1 in the supplemental material shows the proportion of short and long sleep duration in the university students. The proportion of those with sleep duration less than 6 h/d and 7 h/d was 8.4% (95% CI: 5.7% to 12.3%) and 43.9% (95% CI: 36.9% to 51.1%), respectively. The proportion of those with sleep duration more than 8 hours and more than 9 hours was 18.3% (95% CI: 13.2% to 24.8%) and 5.7% (95% CI: 3.2% to 9.9%), respectively.

Forest plot of the mean sleep duration.

CI = confidence interval, ES = effect size.

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Figure 2

Forest plot of the mean sleep duration.

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Sleep Patterns

The sleep patterns of university students are displayed in Table S2 in the supplemental material. The pooled mean bedtime of 5 studies with 8,695 students and available data was 12:51 AM (95% CI: 11:56 PM to 1:50 AM). The proportions of those having bedtime after 11:00 PM and midnight were 72.7% (95% CI: 59.0% to 83.2%) and 23.8% (95% CI: 12.3% to 40.9%), respectively. The pooled mean wake-up time on weekdays of 4 studies with 7,063 students was at 8:04 AM (95% CI: 5:40 AM to 9:27 AM) and the pooled mean wake-up time on weekends from 2 studies was at 9:52 AM (95% CI: 9:02 AM to 10:43 AM). The proportion of wakeup time before 6:00 AM, 6:00 AM to 7:00 AM, and after 7:00 AM were 9.0% (95% CI: 6.0% to 13.4%), 54.5% (95% CI: 35.7% to 72.1%), and 35.7% (95% CI: 7.1% to 79.5%), respectively. The mean sleep latency was 16.96 minutes (95% CI: 13.46 minutes to 20.47 minutes). The proportion of those with sleep latency more than 30 minutes and more than 60 minutes were 25.5% (95% CI: 20.2% to 31.7%) and 5.0% (95% CI: 3.2% to 7.5%), respectively. The proportion of those having an afternoon nap from 10 studies with 19,000 students was 86.4% (95% CI: 76.3% to 92.6%), and the pooled mean afternoon nap duration was 54.24 minutes (95% CI: 37.12 minutes to 42.30 minutes).

Subgroup Analyses

The pooled mean sleep duration and proportion of short (< 6 h/d) and long sleep (> 9 h/d) by sex, survey time, sample size, major (medical and non-medical students), school days, and region are summarized in Table 2. There were no significant associations between sleep durations, sex, different survey times, different sample sizes, medical or non-medical students, and southern and northern regions of China. There was significant difference in sleep duration on school days (6.71 hours, 95% CI: 6.50–6.92) and on weekends (8.36 hours, 95% CI: 8.04–8.67). The pooled mean sleep duration in mainland Chinese students from 11 studies with available data was 7.23 hours (95% CI: 6.92–7.61), which was significantly longer than that in students in Hong Kong, Macao, and Taiwan (6.77 hours, 95% CI: 6.67– 6.88). Short sleep (< 6 h/d) was significantly higher in medical students (16.9%, 95% CI: 10.0% to 27.1%) than in non-medical students (7.4%, 95% CI: 5.8% to 9.5%). Long sleep (> 9 h/d) was more frequent in non-medical students (9.9%, 95% CI: 5.4% to 17.5%) than in medical students (1.6%, 95% CI: 0.5% to 5.0%).

Subgroup analyses of sleep patterns.

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Table 2

Subgroup analyses of sleep patterns.

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Publication Bias

There is no publication bias in sleep duration (Figure 3). Based on the results of visual funnel plot and the Egger test, publication bias was observed in the short sleep group (< 6 h/d); therefore, the “trim and fill” method was performed. Five studies were missing in the short sleep duration group (< 6 hours) (Figure S1 in the supplemental material). The recalculated prevalence of short sleep (< 6 hours) according to the “trim and fill” method was 10.8% (95% CI: 7.58% to 15.2%).

Funnel plot of publication bias for the 18 studies with available data on sleep duration.

Begg test: Z = −0.45, P = .649; Egger test: t = 1.76, 95% confidence interval (−2.7, 6.1), P = .098.

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Figure 3

Funnel plot of publication bias for the 18 studies with available data on sleep duration.

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Sensitivity Analysis

Each study was sequentially excluded in each group and the recalculated combined results did not change significantly, which indicates that none of the individual study significantly influenced the overall meta-analysis result in each group.

DISCUSSION

This was the first meta-analysis that examined sleep duration and sleep patterns in Chinese university students. The pooled mean sleep duration was 7.08 h/d, which is within the range (6.4–7.9 h/d) reported in other countries.3942 The variation between different studies could be partly attributed to the discrepancy in socioeconomic and cultural factors, sampling methods, and measurements. Although the mean sleep duration was within the standard recommended range of 7 to 9 h/d,34 the proportion of students with less than 6 hours sleep duration was 8.4%, which is higher than the corresponding figure of 5.9% found in a nationwide study in Chinese adults.12 The proportion of students with sleep duration less than 7 h/d was 41.3% (95% CI: 35.0% to 47.9%), which is higher than the corresponding figure (33.4%) in a study in Chinese adults.43 The higher proportion of short sleep suggests a high rate of sleep deprivation among Chinese students. The figure found in China is considerably higher than the figures in other countries (eg, 24% in the United Kingdom44 and 30% in Korea41). Several reasons may account for the common short sleep duration in university students. First, late-night activities and early-morning school demands could dramatically reduce sleep duration.7,45 Second, external factors, such as high caffeine consumption and late-night use of electronics may delay sleep onset and shorten sleep.1,41 Third, lack of self-control and regular sleep schedule could contribute to short sleep duration.46

In this study the mean sleep duration did not significantly differ between medical and non-medical students (7.09 versus 7.11 h/d), but the rate of short sleep (< 6 h/d) was significant higher in medical students than in non-medical students (16.9% versus 7.4%). Traditionally, medical students in Chinese universities have more academic stress than other students and many have to shorten their sleep duration in order to meet the academic demands.47 In addition, some studies found that psychological distress, anxiety, depression, and suicidality are relatively common in medical students,48 which could increase the likelihood of short sleep duration. In contrast, long sleep (> 9 h/d) was more frequent in non-medical students than in medical students (9.9% versus 1.6%). Of note, university students in mainland China had a longer sleep duration than their counterparts in Hong Kong, Macao, and Taiwan (7.23 versus 6.77 hours). We assume that this could be partly explained by the differences in study demands, education, and school schedule.

Although there are substantial differences in living habits, economic level, and seasonal and cultural contexts between south and north parts of China, subgroup analysis did not reveal a significant difference between the two areas. In China, most university students live on campus with similar living environment/schedule and relevant living rules, which could offset any difference in sleep duration and patterns. The association between sex and sleep pattern has been inconsistent across studies (eg, male students reported longer sleep than females in Korea, but no significant sex difference was found in Iran and Taiwan).41,42,49 However, no sex difference in sleep pattern and sleep duration was found in this study.

The basic sleep schedules (ie, bedtimes and wake-up times) in this study were similar to those in the United States and Korea.7,41,46,50 The bedtime was 12:51 AM (95 CI%: 11:56 PMto 1:50 AM). More than one-fourth of Chinese students had a sleep latency longer than 30 minutes, which is also consistent with previous findings.49,51 Western university students often got up later and had better sleep quality on weekends.7,52 In this study, the mean sleep time of students on school days was 6.71 hours and 8.36 hours at weekends. The discrepancy in sleep duration between school days and weekend nights was 1.65 hours. Moreover, the mean wake-up time was 8:04 AM on weekdays and 9:52 AM on weekends. The results support the view that university students often shorten their sleep during the weekdays and then attempt to sleep longer on weekends.53,54

Several limitations should be acknowledged. First, the 57 studies only covered 20 of the 33 provinces, autonomous regions, municipalities, or Special Administrative Region in China. Second, as in most observational studies in sleep medicine, sleep information was only based on subjective assessment reported by participants, which may lead to recall bias. In addition, different measures on sleep were used across studies, which could lead to heterogeneity. Third, heterogeneity could not be adequately adjusted for by subgroup analyses, which is consistent with the notion that heterogeneity cannot be avoided in a meta-analysis of epidemiological surveys.55,56

In conclusion, short sleep duration and unhealthy sleep pattern are common in Chinese university students. Its associated sociocultural factors warrant further investigation. Given its harmful effects, efforts should be undertaken to reduce the unhealthy sleep patterns in Chinese university students. In addition, objective measurement of sleep patterns, such as nocturnal polysomnography and actigraphy, should be used in future studies.

DISCLOSURE STATEMENT

The study was supported by the University of Macau (SRG2014-00019-FHS; MYRG2015-00230-FHS; MYRG2016-00005-FHS). The University of Macau had no role in the study design, generating or interpreting the results, or publication of the study. All authors have seen and approved the manuscript. The authors report no conflicts of interest in regard to conducting this study and preparing the manuscript.

ABBREVIATIONS

CI

confidence interval

CNKI

Chinese National Knowledge Infrastructure

ES

effect size

NSF

National Sleep Foundation

SE

standard error

SMD

standardized mean difference

STROBE

Strengthening the Reporting of Observational Studies in Epidemiology

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