PDQ Health » Blog Archive

Practical. Direct. Questioning.

Sleep it off

Author: Peter Jaret

Researchers don’t really know why we sleep. But they do know that sleep deprivation takes its toll. Several recent studies add surprising new reasons to get to bed early tonight.

The slumbering brain

A good night’s sleep helps the mind learn complicated tasks and even recover what seems to have been forgotten, a University of Chicago study reports. Scientists led by Howard Nusbaum, PhD, professor of psychology, recruited 200 college students and taught them to play video games. When the volunteers practiced the games in the morning and were tested 12 hours later in the evening, they had lost about half of their improvement. But when tested again the next morning after a full night of sleep, they showed a 10 percent improvement in their evening score.

“The students probably tested more poorly in the afternoon because following training, some of their waking experiences interfered with training,” Nusbaum speculated. “Those distractions went away when they slept and the brain was able to do its work.”

Previous experiments from the same team found that sleep not only restores what has been learned but also protects memory against loss over the course of the following day.

Even “ultra short episodes of sleep”–AKA brief naps–can boost memory. Volunteers in a study at the University of Dusseldorf in Germany were asked to recall a list of 30 words after a 60-minute interval had passed. When the volunteers took a brief cat nap during the interval, they remembered the words significantly better than when they spent the intervening time awake. Although longer naps were better than short naps in consolidating memory, a snooze of just six minutes improved performance. The researchers concluded that the onset of sleep may initiate the consolidation of memory; once the process is triggered, it works even if sleepers awaken.

Boosting the body’s immune defenses

Sleep also appears to give the immune system time to round up and eliminate invading germs, research shows. The latest evidence comes from a Carnegie Mellon University study in which 153 healthy men and women were quarantined in a hotel and purposely exposed to cold viruses by dripping a controlled amount of viral particles into their nostrils.

Although 88 percent of the volunteers became infected, only about one in three came down with symptoms of a cold. Subects who racked up less than seven hours of sleep were almost three times more likely than those who slept eight or more hours to get bad colds. The greatest risk showed up in people who slept poorly during the night. People who tossed and turned 8 percent or more of the time they were in bed were 5.5 times more likely than sound sleepers to have symptomatic colds.

The immune boosting effects of sleep show up across species, according to results from a study in BMC Evolutionary Biology published in January. Researchers report that animals that sleep longer are less likely to fall prey to parasitic infections. “While awake, animals must be ready to meet the multiple demands on a limited energy supply,” Brian Preston, PhD, a researcher at the Max Planck Institute for Evolutionary Anthropology in Leipsiz, Germany, explained. In other words, they have to hunt for food, mate, and look after their offspring. During sleep, animals can allocate their energy to natural defenses.

Dream away heart disease

By far the most startling discovery from dreamland suggests that a sound sleep can protect against hardening of the arteries. Diana Lauderdale, PhD, and colleagues at the University of Chicago Medical Center found that people who fall short on slumber are more likely to develop calcium buildup in the arteries that supply their hearts, an important risk factor for heart disease.

The investigation followed 495 volunteers who filled out sleep questionnaires and kept a log of time spent in bed. Twenty-seven percent of those who averaged less than five hours a night had calcium buildup in their arteries, compared to only six percent of those who slept seven hours or more.

Why is a mystery. But if you’re burning your candle at both ends, this much is certain: it’s time to get to bed early.