Abstract
We examined the effect of sleep and resilience on stress responses in female Japanese university students during the COVID-19 pandemic. Sleep was measured using the Japanese version of the Pittsburgh Sleep Quality Index (PSQI-J), stress response was evaluated using the Stress Response Scale-18 (SRS-18), and resilience using the Resilience Scale for Students (RS-S). Multiple regression analysis showed that approximately 40% of the SRS-18 score could be explained by PSQI-J score and RS-S score. Subjective sleep quality, daytime dysfunction, and global score of PSQI-J had direct influences on SRS-18.
Keywords: Sleep, Stress response, Resilience, PSQI-J, Japanese female, University students
Introduction
Since the beginning of the COVID-19 pandemic, changes in people’s stress and sleep have been reported from various countries [1]. Mental health, such as stress and depression, has a causal relationship with sleep [2–4]. Resilience, which shows the ability to recover from stress, has also gained attention as a factor affecting sleep in recent years [5]. However, particularly in Japan, there are few reports that comprehensively examine the associations among sleep, stress, and resilience. Kano et al. [6] used a General Health Questionnaire (GHQ) and reported that the Japanese version of the Pittsburgh Sleep Quality Index (PSQI-J) [7] had a significant impact on mental health status; however, this study was conducted before the COVID-19 pandemic.
In the present study, we examined the effect of PSQI-J variables and resilience on stress responses in the context of the COVID-19 pandemic. In particular, we focused on Japanese female university students who are reported to have particularly short sleep duration internationally [8]. The models used in this study are described in Fig. 1.
Fig. 1.
The results of mediation analysis on sleep, resilience, and stress responses. PSQI-J the Japanese version of the Pittsburgh Sleep Quality Index [7]; SRS-18 the new Stress Response Scale-18 [9]; RS-S the Resilience Scale for Students [10]. The numbers in the path from each score of PSQI-J to SRS-18 indicate that the upper row includes the effect of RS-S, whereas the lower row does not include the effect of RS-S. Each score of PSQI-J had a direct influence on SRS-18 as well as mediated influence through RS-S. In particular, the global score of PSQI-J had a strong effect on SRS-18
Methods
The study participants were 103 female university students who were attending a women’s university in Tokyo (Table 1). The average age of the participants was 20.2 ± 1.0 years. The survey was conducted from May to July and in October of 2022 (during regular university semesters). At that time, the number of COVID-19 cases in Tokyo was relatively low, and there was no lockdown. Face-to-face classes were being held at the university, but people were still encouraged to wear non-woven face masks and there was still social anxiety about COVID-19.
Table 1.
Participants’ ages and PSQI-J, SRS-18, and RS-S scores
| Total number = 103 | |
|---|---|
| Age (mean ± SD) | 20.2 ± 1.0 |
| PSQI-J | |
| Global score (mean ± SD) | 6.7 ± 3.5 |
| Score of 6 or higher (number, %) | 59, 57.3% |
| Score of 5 or lower (number, %) | 44, 42.7% |
| Sleep duration (mean ± SD) | 6.4 ± 1.3 |
| More than 7 h (number, %) | 22, 21.4% |
| 7 h or less (number, %) | 81, 78.6% |
| SRS-18 (mean ± SD) | 39.2 ± 13.1 |
| RS-S (mean ± SD) | 71.3 ± 13.2 |
The survey was an anonymous survey conducted using Google Forms. The survey items included age, PSQI-J, the new Stress Response Scale-18 (SRS-18) [9], and the Resilience Scale for Students (RS-S) [10]. SRS-18 was utilized to evaluate subjective stress responses expressed by participants in their daily lives over the previous 2–3 days [9].
After basic statistical analyses were performed, multiple regression analysis was conducted using global score, seven component scores, and RS-S score of PSQI-J [7] as independent variables, and SRS-18 score as a dependent variable. In addition, mediation analysis was conducted using each score. SPSS 28 and HAD version 18 [11] were used for statistical analysis.
The study was a non-invasive anonymous survey. The participants were assured the opportunity to refuse to participate in the study. By submitting their responses, they were considered to have consented to participate in the research.
Results
Using multiple regression analysis, the global score demonstrated the strongest correlation with other PSQI-J scores, resulting in multicollinearity. Therefore, we conducted multiple regression analysis without the global score. The results were significant [R2 = 0.44, Adjusted R2 = 0.39, F(8,88) = 8.54, p < 0.001]. There was a significant effect on subjective sleep quality (Β = 3.08, SE Β = 1.52, β = 0.22, p < 0.05), daytime dysfunction (Β = 3.70, SE Β = 1.52, β = 0.23, p < 0.05), and RS-S score effect (Β = −0.25, SE Β = 11, β = −0.24, p < 0.05). There were no significant interactive effects among each of these two PSQI-J variables and RS-S score.
In addition, the effects of subjective sleep quality, daytime dysfunction, and global score of PSQI-J on SRS-18 and RS-S were analyzed using mediation analysis. The results are shown in Fig. 1a–c.
Discussion
The average sleep duration of the study participants was 6.4 ± 1.3 h, which was short [8]. Poor sleep among Japanese female university students has been reported previously, and our findings taken during the COVID-19 pandemic support these previous studies. The result was similar to an average sleep duration of 6.1 h for Japanese female university students reported in a previous international comparative study [8]. Of 103 participants, 59 (57.3%) had a global score of 6 points or more on the PSQI-J [7].
The result of multiple regression analysis was significant and approximately 40% of the SRS-18 score could be explained by the seven component scores and RS-S score. Subjective sleep quality and daytime dysfunction significantly affected SRS-18 score. Mediation analysis showed that subjective sleep quality, daytime dysfunction, and global score of PSQI-J had significant effects on RS-S score and SRS-18 score. Even when the effect of RS-S score was excluded from the analysis, sleep had a significant direct effect on SRS-18 score. Especially, the effect of global score on SRS-18 score was greater than that of RS-S score on SRS-18 score. These findings suggest that having good quality sleep promote/improve resilience and decrease stress responses. The relationship between sleep as measured by the PSQI-J and stress and resilience has been previously reported internationally, and this study on Japanese female university students during the COVID-19 pandemic supports those findings. Kano et al. [6] assessed mental health status and reported that GHQ score in Japanese university students (83.8% of whom were female) could be explained by PSQI-J global score, stress experiences in daily life, and neuroticism, which were reported to explain 45.3% of mental health status.
There are several limitations to the present study. First, this study was conducted at one women's university. In order to obtain more accurate results, it is necessary to increase the number of participants, include several universities, and compare the results with those of male university students. Second, although this study analyzed sleep as a cause and stress response as a result, it is necessary to investigate the reverse causal relationship as well. Further studies are needed to examine how stress and resilience affect sleep.
Conclusion
The present study used path analysis to investigate the relationships among sleep, stress response, and resilience in Japanese female university students during the COVID-19 pandemic. We found that 41.2% of the stress response could be explained by sleep quality and resilience, and that PSQI-J global score had a stronger influence on stress response than resilience.
Acknowledgements
This study is based on the graduation thesis written in Japanese submitted in January 2023 to the university to which the lead author is affiliated and has been revised for publication.
Funding
No funding was received for this research.
Declarations
Conflict of interest
The authors declare that they have no conflicts of interest regarding this study.
Ethical approval
This study was a non-invasive, anonymous survey. The Ethical Committee at the university where the survey was conducted and where the lead author and corresponding author are affiliated does not require an ethics review for this type of research. The present study was conducted in accordance with the methods approved by this Ethical Committee as well as the 1964 Declaration of Helsinki and its later amendments or comparable ethical standards.
Informed consent
Participants were provided with an explanation of the purpose and summary of the study as well as the potential for publication of results. They were informed that participation was voluntary and that they had the right to refuse participation. Submission of the survey was taken as consent to participate in the study.
Footnotes
Publisher's Note
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