Sleep is important for maintaining and enhancing one’s health. Sleep patterns and sleep problems change along with the life-stage. University students are likely to have late chronotype due to their age-dependent delayed endogenous circadian clock(1), school work, extracurricular activities, club activities, or part-time jobs. Nevertheless, they are forced to wake up early controlled by the social clocks (e.g., early-morning classes or early-morning practice in club activities). Therefore, late chronotype and resulting insufficient sleep are typical sleep problems in this age group. Previous studies have reported that these sleep problems are negatively associated with mental health(2), health-related quality of life(3, 4), and academic performance(5, 6) in the young population.
Sleep-related problems are not rare in nursing students: 9–12% have difficulty initiating sleep, 8–11% have difficulty maintaining sleep, and 8–9% have early morning awakening(7, 8). Furthermore, the prevalence of insomnia, sleep disturbance, or poor sleep ranges from 19 to 56%(7–9). Average sleep duration in nursing students varies among countries: 7 hours in Turkey(10) and 5 hours in Philippines(11),with regional differences in sleep duration among university students in general(12). The percentage of nursing students with short sleep duration was 34–60% (< 7 hours)(7, 13) and 13% (< 6 hours)(9); 11–35% of them had daytime sleepiness(14–16). More than half (59%) of the nursing students took a nap for longer than 30 minutes(7). Taken together, more than a few nursing students may experience insufficient sleep. Furthermore, the previous studies reported that insufficient sleep worsened mental health(17) and health-related quality of life(11), that daytime sleepiness interfered with academic achievement(18), and that subjective poor sleep quality was associated with both physical and mental health(19, 20) in nursing students. Because nursing students have more stress, anxiety, sleep disturbance, and stress-related illness than non-nursing students(21, 22), there are a few studies which recommend stress coping strategies as an approach to address sleep problems(19, 23). However, no studies have focused on age-dependent biological rhythm and chronotype among nursing students.
Chronotype, the tendency towards morningness or eveningness underlying the circadian system, is influenced by age, gender(1), genetics(24), and external environment/circumstances including light exposure(25) and sociocultural conditions(26). Late chronotype is often accompanied by unique eating behaviors (e.g., breakfast skipping, evening energy intake)(27, 28), which result in metabolic disorders including obesity and diabetes(29, 30). In addition, late chronotype is associated with poor mental health(31, 32) and poor academic achievement in university students(33). Generally, nursing university students struggle with academic work (e.g., reports, studying for registered nurse’s licensure exams, graduation research), that consequently bring about delayed bed time, insufficient sleep and worsened daytime functioning. According to the previous study, the amount of academic work was specified as a stressor in nursing students(34). However, no studies have assessed nursing students’ sleep and daily functioning considering their chronotype.
The purpose of the present study is to clarify chronotype and its association with lifestyle, health-related quality of life and academic performance among nursing students. Building healthy lifestyles during their school days may contribute to improving not only their physical/mental health but also the quality of medical services (e.g., prevention of medical accidents, lowering the turnover rate of nurses) in the future.