THE MYTH: You can catch up on sleep over the weekend.

If you’re an undergraduate, chances are that you’re in debt. You’re enrolled in school full-time, plowing through stacks of books, and going out frequently. You’ll just pay it off over the summer or winter break or even on weekends, right?

We’re not discussing financial debt here. Rather, college students are notorious for their sleep debt, the difference between the amount of sleep that their body requires and the hours of shuteye that they’re actually getting. This disparity, dictated by papers, problem sets and partying, is counterproductive. Although providing more time for work, late nights negatively impact your concentration, memory and even vision, with potential detriment to your heart, metabolism, and aging process in the long term. And it’s much harder than you think to repay this debt.

In a study conducted at the Walter Reed Army Institute of Research, Dr. Thomas Balkin and colleagues asked volunteers to sleep for three, five, seven, or nine hours per night for one week. Those snoozing for less than nine hours exhibited progressively worse brain function, although the performance of the five- and seven-hour sleepers stabilized over time. After three nights of eight-hour “recovery sleep,” the performance of the three-hour sleepers improved, achieving the same stable-yet-reduced level of the more moderate sleepers. Meanwhile, the impaired mental and physical ability of the latter didn’t improve at all during the recovery period.

So, the good news is that you can function consistently on as little as four hours of sleep. The bad news is that such sleep debt has lasting effects on your functioning and takes more than sleeping in on Saturday to repay. One research group reported that up to 10 hours of slumber only improves the performance of sleep-deprived individuals for the first few hours of the day, while another study revealed that even a week of eight-hour sleep after several four-hour nights does not eliminate performance lapses.

But while making up for accumulated sleep debt isn’t easy, you can actually save up extra sleep to pay off future debt. A recent study by Balkin’s group demonstrated that eight 10-hour nights before a week of three-hour sleep results in fewer performance lapses than if sleep deprivation is preceded by seven-hour sleep. The researchers dubbed the seven hours “habitual sleep,” in contrast to 10-hour “extended sleep.”

But is “habitual sleep” an accurate description? Is there really a norm? If you’re regularly zipping from class to a cappella rehearsal to late-night study sessions, it may seem like you’ve adapted to needing less rest than your sleepier roommate.

Dr. David Dinges of the University of Pennsylvania doesn’t believe that such adaptation occurs. His group found that volunteers who slept for four or six hours per night for two full weeks, followed by three nights of recovery sleep, experienced a decline in brain function equivalent to pulling two all-nighters. However, Dinges’ leading critic, Loughborough University’s Dr. Jim Horne, points out that a performance deficit equivalent to 16 hours of sleep debt may be evidence of adaptation since Dinges’ subjects actually lost 28-56 sleeping hours. Whether you can adapt to chronic sleep deprivation is thus unresolved.


It takes much longer than one weekend of sleeping in to repay sleep debt, which may have adverse effects on your mental acuity and physical performance. To prepare for the sleep deprivation of exam period or rush week, consider hitting the sack an hour or two earlier the week before. Meanwhile, it isn’t yet clear whether gradual shortening of sleeping hours effectively habituates you to deprivation, so stick to saving up and repaying your debt for now.

Michaela Panter is a fourth-year graduate student in the Department of Immunobiology.