The American comedian Ron White says, “You can’t fix stupid!” However, in the workplace you can prevent some of the stupidity caused by mental fatigue.
Compare these dictionary definitions of “stupid” to how you feel when you have missed too much sleep: in a state of mental numbness, slow to learn or understand, tending to make poor decisions or careless mistakes, stupefied. When stupefied, human operators become the weakest link in a human-machine system; the whole system may fail or produce erroneous results because of that weakness.
Mental fatigue is caused mainly by a lack of adequate sleep. Many folks view sleep as a passive, vegetative state. This is an incorrect assumption based largely on classic novels, plays and poetry. In fact, sleep is a complex activity of the brain. For example:
- the brain generates sleep stages, including slow-wave sleep (SWS) and rapid-eye-movement (REM) sleep
- the stages occur in an orderly manner at night with a 90-minute cycle
- SWS is associated with a release of growth hormone from the brain
- sleep is associated with memory consolidation
These activities are easily impaired by working the night shift or engaging in willful wakefulness at night; ingesting caffeine, alcohol, or prescription or over-the-counter drugs; by indigestion or chronic pain; and by sleep pathologies such as obstructive sleep apnea.
Mental fatigue is also caused by disruptions of circadian rhythms induced by activities such as shift work or changing time zones (jet lag). Circadian rhythms are normal, 24-hour rhythms in human cognitive and physical performance. The word comes from the Latin roots circa, about, and dia, a day. The circadian rhythm of mental performance parallels that of body temperature, with a trough in the pre-dawn hours and a high point in the evening.
The highest relative risk of motor vehicle accidents and industrial errors occurs during the pre-dawn hours. The mid-afternoon is also a risky time because of an effect of the first harmonic of this circadian rhythm. Risk may increase at other times of the day and night, too, if a worker has not practiced good sleep hygiene.
What can you do to minimize the presence of fatigue-impaired workers in your operation? One approach is to be a myth-buster.
For instance, when an employee says, “I can sleep when I die,” put this into perspective and explain that good sleep hygiene is essential to being safe at work, and that it is an inappropriate attitude for workers in safety-sensitive positions. Sleep hygiene information is available from the National Sleep Foundation.
If shift schedulers say “24/7 scheduling is an art that cannot be quantified,” tell them that a quantitative approach to scheduling was developed in the 1970s. (Refer to Systematic selection of shift plans for continuous production with the aid of work-physiological criteria, Appl Ergon 10(1) 1979 and Hours of work and shiftwork, Ergonomics 19(3) 1976.) In addition, if you are told that fatigue cannot be measured, you can state with authority that sleep has been modeled and quantified scientifically for more than 50 years and fatigue for 15 years.
If there is a “toughness” or macho attitude suggesting that other-industry shiftwork and rest guidelines are not needed here, suggest that this is true only if these employees are not human.
Finally, you likely will encounter denial: “Fatigue doesn’t affect my performance. I’ve worked fatigued before with no issues. That means I was safe, right?” In response, you can point out that this is like saying, “I was able to drive home drunk and didn’t hit anything or get arrested. That means I was safe, right?”