The following reports summarize some of the findings presented at the 23rd Annual Meeting of the Associated Professional Sleep Societies.
SEATTLE—Caffeine use prevents increased risk taking that occurs after several nights of total sleep deprivation, reported Major William D. S. Killgore, PhD, of Walter Reed Army Institute of Research in Silver Spring, Maryland, and Harvard Medical School in Belmont, Massachusetts.
According to Dr. Killgore, sleep deprivation may not have a simple linear effect on risk taking; however, there may be a “breaking point” during which a person may show a drastic release in his or her ability to control or inhibit behavior. In this study, caffeine seemed to protect against that breaking point.
The study involved 25 healthy volunteers (21 men) between the ages of 20 and 35 who had been deprived of sleep for three nights. In a double-blind administration, participants received 200 mg of caffeine gum or identical placebo gum bihourly each morning from 1 am to 7 am during the period of sleep deprivation.
At midmorning, subjects participated in a task of risky behavior that requires expenditure effort—the Balloon Analog Risk Task (BART)—during which participants were asked to inflate virtual balloons on a computer and try to “cash in” their value before the balloons popped. The bigger the balloon, the more money it was worth.
Results indicated that despite extreme sleep deprivation, participants who had consumed caffeine did not exhibit increased risky behavior on BART.
Participants who received the placebo were unchanged from baseline on the cost/benefit ratio of the BART at 51 hours of sleep deprivation but showed a significant increase in risk taking behavior by 75 hours. The caffeine group remained unchanged from baseline at either 51 or 75 hours of wakefulness and was significantly less risky than the placebo group at 75 hours.
“People who were awake for three days straight became more impulsive and acted with less regard for consequences,” said Dr. Killgore. “However, if they had consumed caffeine each night (about the equivalent of one to two cups of coffee every two hours from just after midnight until dawn), they showed no increase in risky behavior.”
According to Dr. Killgore, this study looked at the most extreme range of sleep deprivation, so under normal circumstances, most people will not experience such effects.
However, findings from a previous study showed that people who were chronically restricted to three hours of sleep per night for a week showed a progressive increase in risk-taking behavior during the same task. Thus, it is possible that a similar breaking point occurs with longer periods of chronic sleep deprivation, though further research is still necessary.
Older Adults Are Less Affected by Sleep Deprivation Than Younger Adults During Cognitive Performance
Older adults are able to retain better cognitive functioning during sleep deprivation than young adults, according to Sean Drummond, PhD, of the University of California, San Diego and the VA San Diego Healthcare System.
The study included 33 older adults and 27 younger adults. The performance of older and younger adults was compared on three distinct cognitive tasks before and after 36 hours of sleep deprivation.
Older adults (ages 59 through 82) showed more resilience to total sleep deprivation (TSD) than younger adults (ages 19 to 38) on a range of measures of cognitive performance, including working memory, selective attention/inhibition, and verbal encoding and retrieval. Performance of younger adults significantly declined on all three tasks during TSD, while that of older adults did not change significantly.
Dr. Drummond suggested that older adults might have performed better, because only very healthy people were included from that age-group, which may have caused a selection bias that does not exist in younger adults. “It may be that older adults who remain the healthiest late in life are less vulnerable to a variety of stressors, not just sleep loss,” he said.
According to Dr. Drummond, sacrificing sleep to study or work is a false trade-off; findings of this study and many others show that sleep deprivation produces impaired performances across a variety of different tests.
People With Chronic Insomnia Require Increased Brain Activation to Maintain Normal Daily Function
Patients with chronic primary insomnia have higher levels of brain activation while undergoing a working memory test, compared with normal sleepers.
The study included 12 people with primary insomnia (six females) with an average age of 39.4, and nine good sleepers (four females) with an average age of 35.7. Performance was compared between the two groups on a working memory task. fMRI scans taken during the task were also compared. Behavioral performance was measured by reaction time for correct responses, number of correct responses, and number of errors committed.