engleski

Effects of sleep preferences and sleep patterns on daytime functioning of adolescents attending school in two shifts

When school timetable is arranged in weekly rotating morning- and afternoon shifts, adolescents go to sleep later, wake up later, and sleep longer both on weekends and on afternoon shift week. In such a system there are pronounced irregularities of bedtime and sleep duration but better fulfillment of adolescents' sleep need. This study examined the relative importance of sleep patterns in two-shift school system for daytime functioning of adolescents, taking into account other sleep characteristics that can affect waking behaviour. A stratified sample of 2363 students (52% females) from 12 elementary and 12 high schools in Zagreb were surveyed by means of the Croatian version of School Sleep Habits Survey (Wolfson & Carskadon, Child Dev 1998 ; 69: 875-87). Their age ranged from 10 to 20 years (mean 14.3 years). The analysed measures of daytime functioning included Sleepiness, Depressed Mood, number of injuries in a six-month period and self reported school grades. Hierarchical multiple regression analyses were performed for each variable of daytime functioning with six blocks of independent variables: control variables (age, gender), preference variables (morningness, sleep need), sleep duration on morning shift week, sleep quality (difficulty falling asleep, difficulty staying asleep, waking up too early, nightmares/bad dreams), bedtime irregularity (weekend and afternoon shift with respect to morning shift), and sleep extension (weekend and afternoon shift with respect to morning shift). The significant multiple regression coefficient were found for all dependent variables (Sleepiness R =.48, p<.001 ; Depressed Mood R= .61, p<.001 ; injuries R= .27, p<.001 ; grades R= .42, p<.001). After controlling for age and gender, sleep preferences, sleep duration, sleep quality, bedtime irregularity and sleep extension accounted for 16% of variance in Sleepiness, 15% in Depressed Mood, 6% in injuries and 5% in grades. Higher daytime sleepiness was reported in adolescents with evening preferences, shorter sleep on morning shift week and more bad dreams. More depressed mood was reported in adolescents with evening preferences, having difficulties falling asleep, bad dreams and premature waking, and those with smaller extension of sleep on afternoon shift. More injuries were reported in adolescents with evening preferences and shorter sleep on morning shift week. Preferences for late phase and longer sleep had negative effects on school grades. Phase Preferences Consistently Predict Daytime Functioning and Sleep Extension has a Small Positive Effect on Mood.

sleepiness; depressed mood; injuries; school grades

DOI: 10.1111/j.1365-2869.2008.00690.x