If you’re exhausted at the end of a long day and are running on less than optimal sleep, don’t make tough decisions.

We know that sleep deprivation can be serious. It was cited as a factor in the Chernobyl nuclear meltdown, the Exxon Valdez disaster and the Challenger explosion. While you’re probably not likely to have control over projects of this magnitude, simply getting behind the wheel while sleepy can be dangerous. The National Highway Traffic Safety Administration cites that 100,000 car accidents are directly related to fatigue.

While we mostly understand that exhaustion can affect our reaction times, we don’t always consider the impact on our decision making abilities. We should. You’re essentially drunk. From medscape.org:

Alarmingly, though, studies show that when an individual has been awake for as few as 17 hours straight, their cognitive and psychomotor performance deteriorates to equal that of someone with a blood alcohol level of .05% (about 1-2 alcoholic drinks, depending on body weight and speed of consumption).

After 24 hours of sustained wakefulness, one’s impairment mirrors that of someone who has had 2-3 alcoholic drinks and whose blood alcohol is 0.1%, a level that is considered legally drunk in the United States. The finding that moderate levels of fatigue produce performance decrements that are greater than those induced by alcohol intoxication has been confirmed in other investigations.

We all know that people make bad decisions under the influence of a few drinks. Stop me if you’ve heard this one before. A human walks into a bar and throws back a few shots of Patron. That human catches the eye of another human, who has been crushing vodka sodas. The next morning, the humans wake up and can’t believe they slept together. Sleep deprivation works similarly.  From a study published in the Psychonomic bulletin and review:

The results showed that sleep deprivation affects multiple components of cognitive processing, ranging from stimulus processing to peripheral nondecision processes. Thus, sleep deprivation appears to have wide-ranging effects: Reduced attentional arousal and impaired central processing combine to produce an overall decline in cognitive functioning.

Exercising reasonable judgment while under the influence is monumentally more difficult. Would you make a decision about who should become your business partner before sobering up? Maybe you would, but you shouldn’t. Similarly, you’ll want to wait until you you’re well rested before working on your most meaningful tasks. From a study published in the Journal of Neuroscience:

A single night of sleep deprivation (SD) evoked a strategy shift during risky decision making such that healthy human volunteers moved from defending against losses to seeking increased gains.

In other words, you’re more likely to take chances you wouldn’t otherwise take if you’re tired. Your brain simply doesn’t evaluate rewards and consequences the same way. This makes sense; we all know we don’t feel our best when we’re tired. In fact, we tend to make poor choices without even thinking about it, especially with respect to our diets. From Matthew Walker, professor of psychology and neuroscience:

What we have discovered is that high-level brain regions required for complex judgments and decisions become blunted by a lack of sleep, while more primal brain structures that control motivation and desire are amplified… high-calorie foods also became significantly more desirable when participants were sleep-deprived. This combination of altered brain activity and decision-making may help explain why people who sleep less also tend to be overweight or obese.”

This often leads to a downward spiral. We make a D minus decision because we’re fatigued and wanting to feel better. But now we’re still tired, irritable and feeling guilty over that decision. So we begin examining the areas of our lives to make sweeping changes. We come up with drastic options that we can’t possibly adhere to.

Next time you find yourself in this cycle, wait until after a solid night’s sleep and work a coherent process.

Sleep well,

Kap