the aim here is to constrict the time spent in
bed to the actual time spent asleep. A sleep diary is kept for circa
two weeks to establish the average sleep duration. The patient is
then only allowed to stay in bed for that amount of time (but ideally
not less than 5 hours20). This may initially cause daytime sleepiness,
but the time window is gradually increased over a number of weeks
until adequate sleep duration is achieved.