Directors: Antonio M. Battro and Kurt W. Fischer
Program officer: María Lourdes Majdalani
Sleep and academic performance of adolescents attending school in two shifts
The adolescents show pronounced differences between their sleep-wake patterns on school days and days off. They generally do not get enough sleep during school days, since they tend to delay their bedtimes even on school week when they are obliged to wake up early. Some studies showed that inadequate sleep timing, duration and quality were related to poor academic performance in adolescents. In Croatia the majority of elementary and high schools organize classes in weekly rotating morning and afternoon shifts. The results of our previous studies indicated the beneficial effects of such a school schedule regarding the sleep duration and levels of daytime sleepiness in adolescents. In this study we wanted to examine the relationship between self-reported characteristics of sleep and academic performance in high school adolescents attending classes one week in the morning and the other in the afternoon. We analyzed the data of 312 second grade high school students (67% females, dominant age 16 years) who applied to participate in two sleep studies conducted by our laboratory. They answered the selection questionnaire comprising general questions about themselves and members of their families, questions on their academic performance, sleep and health, and a standardized Morningness-Eveningness scale for children (Carskadon MA, Vieira C, Acebo C. Sleep 1993;16:258-62).
The ANOVAs showed significant differences in bedtimes, wake-up times and time in bed between three situations: morning shift, afternoon shift, and weekend. Bedtime and wake-up time were the earliest on school days of morning schedule, followed by school days of afternoon schedule and then by weekend days. Time in bed was the shortest on school days of morning schedule and the longest on weekend. Boys went to bed later than girls regardless of the situation, but we found no differences in wake-up times or time in bed between boys and girls. Mean self-rated academic performance of the girls was somewhat higher than that of the boys. The correlation analyses showed small but significant association between academic performance, morningness-eveningness and some sleep variables. When phase preferences and gender were controlled for, poorer academic performance was associated with later bedtimes in all situations, and with later wake-up times on weekend. On the other hand, academic performance was not related to wake-up times on school days or time in bed in any of three situations. It was also not associated with sleep quality or frequency of daytime napping.
Sleep characteristics and academic performance are influenced by various psychosocial factors. Therefore one could not expect high correlations between the variables in question. Even though our study did not corroborate the relationship between sleep duration, sleep quality and academic performance, it did show that later bedtimes were associated with lower school grades. Further studies are needed to establish other factors that contribute to both bedtime delay and poor academic performance in adolescents.