Morningness–eveningness and sleep patterns of adolescents attending school in two rotating shifts

Abstract

School system in which classes are scheduled 1 week in the morning and the other in the afternoon, and in which students rotate schedule every week, fosters sleep irregularity. In this study, we examined morningness-eveningness of adolescents who were involved in such schedule of school time and explored relationship between their circadian preferences and sleep characteristics. A large sample of 2287 students between the ages 11 and 18 years (52% girls) from 24 schools in Croatia was studied. The School Sleep Habits Survey was modified to enable differentiation of sleep patterns between the two school schedules and weekends. Two measures of ME were used: the Morningness-Eveningness Scale for Children (MESC) and mid-sleep time on weekends (MSFsc). Both measures showed a shift to eveningness starting between the ages 12 and 13 (MESC), or 13 and 14 (MSFsc). However, MESC demonstrated a plateau in the shift in older adolescent whereas MSFsc indicated further progress of phase delay. Significant differences in sleep timing and duration were found between three chronotype groups (Morning, Intermediate, and Evening). Generally, Evening types went to bed and woke up the latest in all situations. Their sleep duration was the shortest on school week with morning schedule. On weekends Morning types slept shorter than other two chronotype groups. On school week with afternoon schedule all chronotype groups slept close to the recommended 9 h. All three chronotype groups delayed their bedtimes and wake-up times, and extended their sleep in situations with fewer constraints on sleep timing (i.e. afternoon school schedule, and weekends versus morning school schedule). Expectedly, the evening types showed the greatest sleep irregularity. The findings of this study suggest that the Croatian school system fosters sleep irregularity, but provides more opportunity for fulfilling sleep need of all chronotype groups of adolescents. Age effects on morningness-eveningness observed in Croatian adolescent do not seem to be different from those observed in adolescents from other countries involved in a regular morning school schedule. Further studies are necessary to explore differences in the trend of shift towards eveningness found between the two measures of morningness-eveningness in this, as well as in other studies.

Sleep–wake habits and circadian preference in Mexican secondary school

“…Adolescents who attended classes in an afternoon shift slept an average of 9 hours and 23 minutes during the week, which is slightly higher than has been reported in countries where the school system has an afternoon shift such as Croatia [72], Brazil [67,73], Greece [74], and even in an earlier study in Mexico [53] which report an average weekday sleep duration of 8 to 8.30 hours. Thus adolescents who have the opportunity to attend classes in an afternoon shift have a substantial sleep duration that meets the recommended duration [6,[60][61][62][63][64][65][66][67][68][69][70], regardless of their chronotype.…”

“…This lack of sleep brings with it a number of sleep problems, such as insomnia, daytime sleepiness, and disrupted sleep patterns [36], with the consequence of unsuitable conditions for school learning [89]. In comparison, adolescents who attend classes it an afternoon shift have better sleeping conditions, regardless of whether they have an orientation to eveningness or morningness, as also shown by Koscec et al [72]. In Mexico, this afternoon school shift is permanently implemented, so this allows us to compare the morning and afternoon shifts.…”

Advancing a Biopsychosocial and Contextual Model of Sleep in Adolescence: A Review and Introduction to the Special Issue

“…Nonetheless, the difference in school start times points to at least one of the likely contributors to Australian adolescents obtaining more sleep than adolescents in the US. In addition, a study of Croatian adolescents provides additional evidence of the effect of school schedule on youth's sleep patterns (Košćec et al 2014). Due to a lack of school space to accommodate all students simultaneously, most schools in Croatia have students on alternating schedules whereby students attend classes in the morning for 1 week and then in the afternoon the next week.…”

“…Due to a lack of school space to accommodate all students simultaneously, most schools in Croatia have students on alternating schedules whereby students attend classes in the morning for 1 week and then in the afternoon the next week. Using this naturally-occurring two-shift schedule, Košćec et al (2014) found that all youth (regardless of chronotype) delayed their bedtimes and wake times when in the afternoon versus morning school schedule. However, youth with an evening chronotype (as opposed to a morning or intermediate chronotype) showed the greatest irregularity, obtaining almost 2 fewer hours of sleep per night when on the morning school schedule than the afternoon school schedule.…”

Social jetlag, academic achievement and cognitive performance: Understanding gender/sex differences

“…Although high school begins early in the morning compared to elementary school and this change toward earlier start times during adolescence is not universal (Koscec et al, 2014), this misalignment between biological (evening preference) and social (early school time) time is very common among adolescents, who tend to be much later chronotypes than other age groups (Roenneberg et al, 2004). This mismatch between internal and external rhythms has been considered as a risk factor for low academic performance and poor health (Wittmann et al, 2006), and despite the fact that the effects of sleep deprivation have been extensively studied, there are not many studies which consider the effects of interindividual variables such as morningnesseveningness.…”