Sleepiness can make you less effective at work. But unfortunately, it can also make you very unsafe. Sleepiness clouds your thinking and causes you to make more errors, react slower, and use poorer judgment than you do when you're alert. One of the most dangerous aspects of sleepiness is that people often misjudge their own state of mind and abilities, believing that they are able to handle important decisions and tasks, when in fact they are not.
Many large studies have found a relationship between sleepiness and work-related injuries. Highly sleepy workers are 70 percent more likely to be involved in accidents than non-sleepy workers, and workers with chronic insomnia (difficulty getting to or staying asleep) are far more likely than well-rested individuals to report industrial accidents or injuries. People with excessive sleepiness who also snore (a potential sign of sleep apnea) are twice as likely to be involved in workplace accidents. And tragically, in one Swedish study of nearly 50,000 people, those with sleep problems were nearly twice as likely to die in a work-related accident.
Sleepiness is also thought to have played a role in some of the most devastating environmental health disasters in history. In the case of the Three Mile Island nuclear power plant incident, which occurred at 4:00 a.m., overnight shift workers failed to respond quickly and appropriately to a mechanical problem that caused a near meltdown; sleepiness is thought to be partly to blame. The nuclear plant disaster at Chernobyl, which took place at 1:30 a.m., is also linked to human error influenced by sleepiness. Sleep loss is thought to have played a role in the Exxon Valdez oil tanker spill, and the Space Shuttle Challenger accident (where managers at the flight center were known to be working irregular hours on very little sleep). These and other accidents, both small and large scale, highlight the potentially devastating consequences of lapses in judgment and accuracy that result from sleepiness.