http://healthysleep.med.harvard.edu/healthy/matters/consequences/sleep-performance-and-public-safety
In addition to these normal fluctuations, not getting enough sleep—whether for just one night or over the course of weeks to months—has a significant effect on our ability to function. Sleep deprivation negatively impacts our mood, our ability to focus, and our ability to access higher-level cognitive functions. The combination of these factors is what we generally refer to as mental performance. In the laboratory, researchers use scientific studies to determine just how significantly varying levels of sleep disturbance impact various types of mental performance.
The prefrontal cortex is responsible for many higher-level cognitive functions and is particularly vulnerable to a lack of sleep.
The most immediate effect of sleep deprivation is sleepiness. In our daily lives, we may experience this as a general fatigue, lack of motivation, or even the experience of nodding off. In the research or clinical setting, scientists measure sleepiness using a variety of methods. After a period of sleep deprivation, there are noticeable changes in brain activity, as measured by an electroencephalogram (EEG). These changes correspond to a lower level of alertness and a general propensity to sleep. Any period of continual wakefulness beyond the typical 16 hours or so will generally lead to these measurable changes.
In addition to the feeling of sleepiness and changes in brain activity that accompany a night without sleep, other measures of performance are noticeably altered. Concentration, working memory, mathematical capacity, and logical reasoning are all aspects of cognitive function compromised by sleep deprivation. However, not all of these functions rely on the same regions of the brain, nor are they impacted by sleep deprivation to the same degree. For example, the region of the brain known as the prefrontal cortex (PFC) is responsible for many higher-level cognitive functions and is particularly vulnerable to a lack of sleep. As a result, people who are sleep deprived will begin to show deficits in many tasks that require logical reasoning or complex thought.
Bookshelf
Harrison Y, Horne J. 2000. The impact of sleep deprivation on decision making: A review. Journal of Experimental Psychology: Applied. 6:236-249.
Landrigan CP, Rothschild JM, Cronin JW, Kaushal R, Burdick E, Katz JT, Lilly CM, Stone PH, Lockley SW, Bates DW, Czeisler CA. 2004. Effect of reducing interns' work hours on serious medical errors in intensive care units. New England Journal of Medicine. 351:1838-1848.
Determining just how much performance is affected by sleep loss is difficult, in part because of factors such as individual differences in sensitivity to sleep deprivation, as well as individual differences in motivation to stay alert despite sleep loss. Even so, the evidence is clear that a lack of sleep leads to poor performance. As the prevalence of inadequate sleep grows and the demands of the workplace change, it becomes increasingly critical that we recognize and take action to mitigate the impact that insufficient sleep has on our safety and well-being.
