Bleary eyed, Mike Luka dragged himself through the front door of his house Tuesday evening and sank into the living-room couch.
"Wake me up in 30 minutes so I can get ready for the next test," he said through the down pillow in which he had buried his head.
With two tests remaining before three finals next week, Luka, like many students at the University of Houston, is struggling through the last weeks of the semester, trying to squeeze extra studying into an already hectic schedule.
Many students sacrifice sleep for studies as the end of the semester approaches, and the projects and tests become more valuable.
"I've slept five hours total in the last three days," Luka, a graduate math student, said after waking. "I need to ace these last tests."
But while test scores might reflect the additional effort, accompanying the scarified sleep is an additional risk of catching an illness.
According to Bola Akanwobi, a general practitioner for the Kelsey-Seybold Clinic, there is an increase in the number of cases of the common cold at the end of every semester.
The combination of inadequate sleep and extra stress diminishes the body's ability to defend itself against viral invasions, he said.
"The average human needs to sleep for at least six hours each night," he said. "Without six, your body is vulnerable to attack."
Regardless, getting enough sleep is not an option for some students. Nashika Stokes, a senior political science major, pointed to the slew of tests approaching as a rationale for shortened nights.
"When I have four tests worth about 40 percent of my GPA for the semester, sleep kind of gets pushed to the back of my mind," she said.
Both Luka and Stokes suffer from the lingering effects of recent colds and their studies are occasionally interrupted by coughing fits.
With the help of cough drops and Ny-Quil, they persevere, with or without sleep.
Akanwobi suggested that anyone who might suffer from a lack of sleep should take extra precautions against illness. Precautions might include eating more fruits and vegetables as well as taking vitamin C and zinc, both of which are good starts for students who want to stay healthy for the holidays.
A half hour after his collapse into slumber, a timekeeping roommate prodded Luka. He coughed himself awake and begged to sleep a little longer.
"Just 15 more minutes," he said.
While the extra few minutes may not make up for sleepless nights, Akanwobi said any sleep you can get is important.
"The immune system can be boosted by the right diet, but nothing can replace sleep," he said.