Regular bedtime for restful sleep
Going to bed at the same time each night is just as important for success as getting a long night's sleep, research suggests.
Harvard University researchers found the benefit of sleeping for seven to nine hours a night can be squandered by not going to sleep at a regular time.
The implication is that a shortage of sleep can be, in part, offset by having a reliable routine.
The research suggests that napping to top up on sleep missed does not help.
Scientists at Brigham and Women's Hospital in Harvard monitored 61 undergraduates for a month, measuring the quantity and timings of their sleep. They found those who kept regular patterns performed better academically.
The comparative benefit was similar to that observed between people getting the right amount of sleep and those sleep-deprived.
Charles Czeisler, a co-author of the research, said in students whose sleep times were inconsistent, classes and exams scheduled for 9am felt like they were at 6am, according to their body clock, a time when performance is impaired.
"Our results indicate that going to sleep and waking up at approximately the same time is as important as the number of hours one sleeps."