**Background:** The COVID-19 pandemic led to widespread stay-at-home orders and a sudden transition to remote learning for university students. University students are particularly vulnerable to sleep problems due to their age-dependent delayed endogenous circadian clock, and nursing students face additional stressors including clinical training disruptions, fear of infection, and high academic pressure. While previous studies documented delayed sleep-wake rhythms and increased sleep duration during the pandemic, the impact of returning to campus on sleep had not been investigated. This study aimed to examine changes in sleep during stay-at-home and after returning to campus among nursing university students.
**Methods:** The study was conducted at a university in Tokyo, Japan. Paper-based questionnaires were distributed to sophomores between October and November 2019 (response rate: 20.2%, n=26). Web-based surveys were sent to all nursing students in June 2020 (response rate: 60.8%, n=307) and June–July 2021 (response rate: 46.5%, n=224). Study 1 analyzed 18 paired data from participants taking remote classes in 2020 compared to their 2019 data. Study 2 analyzed 91 paired data from participants taking remote classes in 2020 and on-campus classes in 2021. Measures included sleep patterns (bedtime, wake-up time, sleep duration, nap duration), sleep debt (difference between weekday and weekend sleep duration), midpoint of sleep on free days with correction (MSFsc), social jetlag, the Epworth Sleepiness Scale (ESS, cutoff ≥11 for excessive daytime sleepiness), the Athens Insomnia Scale (AIS, cutoff >5 for possible insomnia), and self-reported sleep-related symptoms (difficulty initiating sleep [DIS], difficulty maintaining sleep [DMS], early morning awakening [EMA], difficulty in morning awakening [DMA], nightmares, hypnagogic hallucinations [HH], sleep paralysis [SP]). Statistical analyses included Wilcoxon signed-rank tests, chi-square tests with residual analyses, and logistic regression analysis adjusted for sex and grade.
**Key Results:** In Study 1 (n=18), staying at home due to COVID-19 was associated with significantly delayed bedtime on weekends (1:00±0:57 to 1:42±1:11, p<0.05), wake-up time on weekdays (6:59±0:39 to 8:55±1:47, p<0.05) and weekends (9:41±1:12 to 10:05±1:33, p<0.05), and delayed MSFsc (4:20±0:36 to 5:32±1:18, p<0.05). Sleep duration on weekdays increased from 5.8±1.1 to 7.4±1.2 hours (p<0.05), sleep debt decreased from 2.6±1.7 to 1.0±1.2 hours (p<0.05), and social jetlag decreased from 1.3±0.7 to 0.7±0.9 hours (p<0.05). ESS scores improved from 12.7±4.1 to 8.3±4.2 (p<0.05), but AIS scores worsened from 5.4±2.5 to 8.7±3.6 (p<0.05), and the prevalence of DIS increased from 28% to 72% (p<0.05). In Study 2 (n=91), returning to campus was associated with advanced wake-up time on weekdays (8:32±1:35 to 7:03±1:02, p<0.05) and weekends (9:17±1:36 to 8:49±1:35, p<0.05), advanced MSFsc (5:12±1:21 to 4:23±1:10, p<0.05), shortened weekday sleep duration (7.6±1.2 to 6.2±1.2 hours, p<0.05), increased sleep debt (0.4±0.8 to 1.5±1.6 hours, p<0.05), increased social jetlag (0.6±0.8 to 1.0±0.9 hours, p<0.05), worsened ESS scores (9.3±4.5 to 12.3±4.6, p<0.05), and worsened AIS scores (7.1±4.1 to 9.1±3.6, p<0.05), though DIS prevalence decreased from 68% to 50% (p<0.05). Of the 91 students, 34 (37%) showed an advanced midpoint of sleep of more than one hour. This group had higher prevalence of sleep paralysis (27% vs. 2%, p<0.05) and nightmares (74% vs. 47%, p<0.05), but lower ESS scores (10.8±4.4 vs. 13.2±4.6, p<0.05) compared to those without advanced midpoint. Multiple logistic regression showed that commute time over one hour was significantly associated with advanced midpoint of sleep (aOR 3.29, 95%CI: 1.24–8.72, p<0.05).
**Clinical Implications:** This study demonstrates that while stay-at-home measures resolved sleep deficits and improved daytime sleepiness in nursing students, returning to campus with earlier class start times led to advanced wake-up times, shortened sleep duration, increased sleep debt, and worsened insomnia and daytime sleepiness. The high prevalence of REM parasomnias (sleep paralysis and nightmares) among students with advanced midpoint of sleep suggests that abrupt shifts in sleep-wake timing may disrupt REM sleep regulation. Students with delayed midpoint of sleep after returning to campus had higher daytime sleepiness and more frequent breakfast skipping, indicating potential risks for poor mental/physical health and academic performance. The association between commute time over one hour and advanced midpoint of sleep highlights the role of social/environmental factors in shaping students' sleep patterns. The authors recommend that educational environments—including curriculum design, class schedules, and class formats—should be established considering students' age-dependent biological rhythms, and suggest that student-selectable combinations of on-campus and online classes may be beneficial. Limitations include small sample size (especially Study 1, n=18), single-university design, differences in sampling methods between years (paper-based vs. web-based), and potential sampling bias.