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Is Being Tired Like Being Drunk? 17 to 19 Hours Awake Matched Drinking

Hiroki ObaraHiroki Obara · DeveloperBrain MondoBrainDojo
Is Being Tired Like Being Drunk? 17 to 19 Hours Awake Matched Drinking

After 17 to 19 hours awake, performance on some tests was as bad as, or worse than, at a blood alcohol concentration of 0.05%. That is the result of an experiment by Williamson and Feyer, published in Occupational and Environmental Medicine in 2000.

In a Brain Mondo short video, I introduced this study in about 40 seconds. In this post I write about the details that did not fit in the video, driving studies that used the same comparison, and how far a tired person can tell how tired they are.

Video: Sleep facts: Sleep loss and drinking (Japanese)

The video is in Japanese.

What the experiment was

The aim of the study was to compare, on the same scale, how much sleep loss and alcohol affect performance.

There were 39 participants. Thirty worked in the transport industry and nine were from the army. The researchers chose people whose jobs keep them close to fatigue, not students.

The same participants went through two conditions. In one, they stayed awake without sleep for 28 hours. In the other, they drank measured doses of alcohol, up to a blood alcohol concentration of about 0.1%. They took the same tests in both conditions, and the scores were compared.

Comparing within the same people matters. Some people react fast and some slowly, but if your own “score after drinking” is the yardstick, the effect of sleep loss can be expressed in a form anyone understands: how much alcohol it is equivalent to.

Result: 0.05% after 17 to 19 hours

After 17 to 19 hours without sleep, performance on some tests was equivalent to, or worse than, that at a blood alcohol concentration of 0.05%. According to the paper, on the clock this corresponded to between 10:30 pm and 1:00 am.

Nobody had pulled an all-nighter. They had simply got up in the morning, worked, and stayed up late. For many people, 10:30 pm is still an ordinary time to be awake.

On some tests, response speeds were up to 50% slower, and accuracy was clearly poorer than at this alcohol level.

With longer periods awake, performance fell to the level of the largest alcohol dose given to participants, a blood alcohol concentration of 0.1%.

Why compare with alcohol

The 0.05% figure carries some weight. The abstract of a 2006 study I describe below names 0.05% as the legal driving limit in Australia. The title of this paper also speaks of impairment equivalent to legally prescribed levels of alcohol.

Most people know that driving or operating dangerous machinery after drinking is something you must not do. Working late into the night carries almost none of that feeling. In their conclusion, the authors write that the fatigue of sleep deprivation is an important factor likely to compromise the speed and accuracy needed for safety on the road and in industry.

This study translates the danger of sleep loss into a unit everyone grasps by instinct: alcohol. “I’m tired” sounds minor. “It’s the same as having drunk enough to reach 0.05%” sounds quite different.

The same in a driving simulator

The same comparison has been tried with driving, in a study published in Accident Analysis and Prevention in 2001.

In this study, 18 healthy men aged 19 to 35 drove a simulator for 30 minutes at blood alcohol concentrations of 0%, 0.05% and 0.08%. The results were compared with an earlier study of simulated driving during one night of staying awake. The comparison followed the approach used by Dawson and Reid in a 1997 paper in Nature.

For lane position, weaving within the lane and variation in speed, 18.5 hours awake produced changes about as large as 0.05%, and 21 hours as large as 0.08%. On the other hand, deviation from the speed limit and the number of times the car left the road got worse with alcohol than with the matching time awake. The authors say that staying awake as little as 3 hours longer can reduce the ability to keep speed and lane position as much as the legal alcohol limits do.

In addition, a study published in the Journal of Sleep Research in 2003 compared 24 hours of staying awake with a blood alcohol concentration of 0.05%, test by test. Sleep loss caused the bigger drop in the speed of sustained attention, in memory and learning, and in the accuracy of a complex matching task. Alcohol was worse only for the accuracy of memory and learning.

So sleep loss and alcohol do not break things in exactly the same way. Which abilities drop differs a little. Even so, the size of the drop is in a comparable range.

How well can you tell?

The question this raises is how accurately a tired person can sense their own state.

In a study published in Chronobiology International in 2006, 32 participants stayed awake for 40 hours. Every 2 hours, they took a test of reacting quickly to a signal on a screen, and rated on a seven-point scale how well they thought they could drive safely, react quickly in an emergency, and stay in their lane.

Participants’ ratings of themselves dropped at around the same time as their reaction test performance slowed. At 3:00 am, after 19 hours awake from 8:00 am, their ratings for “drive safely” and “react quickly” crossed to the worse side of neutral. The authors say people’s own perceptions do line up with reality to some extent.

However, participants consistently rated the driving ability of someone else in the same situation as poorer than their own. The authors point to this as a concern about overconfidence. The feeling of “I’m tired, but I’m still one of the better ones” probably comes easily to anyone.

What the study does and does not tell us

What reached the level of 0.05% in this experiment was performance on “some tests”. It does not mean every ability turns uniformly into a drunk state. As the 2003 study showed, different abilities drop in different ways.

The participants numbered 39, and they were tested within a single 28-hour stretch without sleep. This experiment alone does not show what happens when each night is a little short over a longer period. I wrote about an experiment with two weeks of six-hour nights in Is Six Hours of Sleep Enough?.

Also, 17 to 19 hours is counted from the time you woke up. The earlier you get up, the earlier that time comes.

Using it in daily life

Here are three ways to apply this study to daily life.

  • Count the hours since you woke up. Rather than how sleepy you feel, use how long you have been awake as the guide. If you got up at 6 am, after 11 pm you have passed the 17 hours in this experiment.
  • Keep important work out of late nights. Work where a mistake carries straight through, such as sending money, checking a contract or writing an important message to someone, belongs to your head after sleep, not late at night. As the video put it, do important work with the head you have after sleeping.
  • Think of late-night driving the way you think of drinking. On a long day, when you drive, judging by how long you have been awake is safer than going by the feeling that you are still fine.

Brain Mondo is a series of daily short videos about the brain, each based on a research paper. BrainDojo is an app for training calculation, memory, attention and more in a few minutes a day, and the once-a-day Brain Dojo Check gives you scores for processing speed, inhibitory control and short-term memory. Seeing in numbers how differently you react in the morning and late at night may make this study feel a little more real.

References

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