Studies show many college students are not getting the amount of sleep necessary to function properly, a practice sleep researchers say can take a toll on much more than the gradebook.

According to data from the American College Health Association’s National College Health Assessment survey from fall 2011, only 9.5 percent of undergraduate students reported getting enough sleep to feel rested for at least six days out of the week; 32.4 percent of undergraduates get adequate sleep for only one to two days in each seven-day period.

Kenneth Lichstein, director of the University’s Sleep Research Project, said the amount of sleep people need to feel rested and function properly varies among individuals, but most require on average between seven and one half and eight hours of sleep per night.

The diversity of UA students’ sleeping patterns lends evidence to Lichstein’s case.

“For me to feel rested, I usually need between three or four hours of sleep,” said Alex Mendoza, a junior majoring in history who usually hits the hay four to five hours each night. “I usually try to go to sleep between midnight and 1 a.m.”

Mendoza said he pulls an “all-nighter,” the practice of keeping awake over the course of an entire night and into the morning, at least twice a week, usually to study for an exam the next day or wrap up some revisions on a paper.

Anthony James, a freshman majoring in microbiology and Spanish, said he needs about eight hours each night to feel rested the next morning but usually only gets six in an average school night.

“Staying up late [for me] would probably be anything past midnight. I am up late almost every night unless I have just had an easy day,” he said. “I try to go to sleep no later than 2 a.m. no matter how much work I have left. It’s just not worth it. I try not to pull all-nighters because they usually don’t work, so I limit them to about once every two weeks.”

Lichstein said once every couple of weeks is still more frequently than anybody needs, as all-nighters hold little value as productive study time.

“Studies show that sleep is crucial for memory consolidation and retention. So if you study hard in the evening, and then you get a good night’s sleep, you should remember a lot of what you learned,” Lichstein said. “But overnight studiers don’t have the benefit of that consolidation, so they will retain less information when it comes time to taking the test the next day.”

According to an article entitled “Sleep and Memory” by the Division of Sleep Medicine at the Harvard Medical School, “research suggests that the most critical period for sleep for memory consolidation is the one immediately following a lesson. Even if sleep is ‘recovered’ on subsequent nights, the brain will be less able to retain and make use of information gathered on the day before the all-nighter.”

Lichstein said a continued pattern of insufficient sleep can also have a substantial negative effect on students’ physical well-being, as regular sleep deprivation has been scientifically linked to compromised immune system efficiency and increased susceptibility to bacterial and viral infections.

Sheena Gregg, assistant director of nutrition education and health services in the College of Community Health Sciences’ Department of Health Promotion and Wellness, said prolonged sleep deprivation can even hit students where it really hurts – at the waistline.

“Limited research has suggested one theory that lack of sleep disrupts the hormone levels that regulate appetite and food intake. Thus, limited or deprived sleep can lead to eventual consumption of larger portion sizes and more frequent snacking that could lead to weight gain,” she said in an emailed statement. “Sleep deprivation also correlates with having lower energy levels, which can translate to students missing their regular exercise routine the next day.”

However, a few nights spent with slim slumber are no cause for nightmares, Lichstein said.

“One really good night of sleep will repair the cognitive damage of multiple nights of sleep deprivation,” he said. “You may have to sleep an extra hour or so, but that excellent night’s sleep can erase any enduring holdups and get you back on the right track.”