Studies show that the brain is adversely affected by sleep deprivation because certain patterns of electrical and chemical activity that occur during sleep are interrupted and the brain cannot function normally. In one study, thirteen healthy adult subjects who usually had normal sleep patterns were kept awake and carefully monitored in a hospital sleep laboratory during a period of 35 hours. During the experiment, the subjects were asked to perform several cognitive tasks, such as arithmetic and word problems, while undergoing magnetic resonance scans of their brain activity. The scans recorded each subject’s brain activity from a rested state through various stages of sleep deprivation over the 35-hour period. The scans produced images showing increased activity in some regions of the brain and decreased activity in others. The researchers found that the temporal lobe of the brain, the region involved in language processing, was activated during verbal tasks in rested subjects but not in sleep-deprived subjects. When subjects were fully rested, their magnetic resonance scans showed that the temporal lobe was very active. However, after several hours without sleep, there was no activity within this region. The effects of the inactivity included slurred speech in the subjects who had gone for prolonged periods with no sleep.

Several studies show that getting fewer than six hours of sleep a night can impair short-term memory, coordination, reaction time, and judgment—thus posing a serious risk of accident or injury. In one study of drivers, researchers reported that sleep deprivation had some of the same hazardous effects as being drunk. They found that people who drove after being awake for 17 to 19 hours performed worse than those with a blood alcohol level of 0.05 percent, the legal limit for drunk driving in most western European countries. The study also found that 16 to 60 percent of road accidents involved sleep deprivation. The researchers concluded that countries with drunk driving laws should consider similar restrictions against sleep-deprived driving.

There are other problems associated with sleep deprivation beyond impaired motor skills and judgment. Drivers who get too little sleep may have higher levels of stress, anxiety and depression, may take unnecessary risks, or may express rage toward other drivers. These dangers affect not only drivers but also people who work long shifts or night shifts, such as medical personnel and other emergency workers. The dangers of sleep deprivation go far beyond the obvious risks and can, in fact, undermine all areas of an individual’s physical and mental health.

Sleep deprivation weakens the immune system, making an individual more prone to diseases such as the common cold and diabetes. Without sleep, the number of disease-fighting white blood cells within the body decreases, as does the activity of the remaining white blood cells. Sleep deprivation has been linked to a decrease in the body’s production of hormones such as insulin. Results of a recent study suggested that healthy young adults who regularly got under 6.5 hours of sleep a night had greater insulin resistance than people who got 7.5 to 8.5 hours of sleep. Insulin resistance is a silent condition in which the pancreas does not make enough insulin or the body is unable to use the insulin that is present. Thus, the muscle and liver cells cannot metabolize the sugar called glucose. As a result, glucose builds up in the bloodstream, setting the stage for diabetes and heart disease.

Glossary:

insomnia: the inability to fall asleep or remain asleep

jet lag: the disruption of bodily rhythms caused by high-speed travel across time zones

cognitive: relating to mental processes