An important contribution was offered by Wolfson
and Carskadon,15 who studied (by means of a
health and behaviour survey with self-reported
grades) sleep patterns and daytime functioning in
about 3000 high school students. They showed that
students with higher grades reported more total
sleep, earlier bedtimes on school nights and
reduced weekend delays of sleep schedules than
students with lower grades. These data of better
performance as a consequence of ‘hygienic’ sleep
patterns were confirmed by several studies indicating
a poorer school achievement, a greater tendency
to fall asleep in school, more difficulties in
concentration and in focusing attention in students
with an evening circadian typology,54 earlier school
starting times55,56 and a mild delayed sleep phase
syndrome.57
Another recent study using surveys and selfratings58
pointed out that time in bed has no
relationship with facility of concentration or paying
attention at school, whereas sleep quality and
feeling rested at school (index of a good night’s
sleep) were highly related to a general measure of
school functioning. Moreover, children without
difficulty getting up displayed more achievement
motivation. This was one of the first studies that
explicitly stressed the relevance of sleep quality