This is a summary of the second lesson of Module 3 of the North American Fatigue Management Program (NAFMP). This module is focused on driver education as part of a Fatigue Management Programs (FMP). Due to the length of this module (157 PowerPoint slides), I have divided this module into several blog posts. This lesson analyzes the components of sleep and alertness.
Features of sleep: We don’t know exactly why, buy sleep is necessary for performance and health. Brain cells grow and create connections during sleep. The brain does not rest during sleep. Sleep is not rest.
Types and stages of sleep: Non-REM. sleep (when there is no Rapid Eye Movement) includes four stages from light to deep sleep in which brain activity is decreased. In REM sleep, the brain is very active, similar to being awake. The name derives from the fact that your eyes move as if you were awake. You enter REM sleep several times throughout the sleep cycle. REM is indicated in blue below:
Sleep inertia: This is the grogginess you feel when you first wake up and can last 20+ minutes. Sleep inertia affects driving, especially during times when it is dark out.
Age and sleep: Adults need 7-8 hours. Older adults sleep more lightly, are more easily awakened, may take more naps and are not more likely to fall asleep while driving. Males under 30 are the highest risk for falling asleep while driving.
Factors affecting sleep and alertness: Factors that affect sleep quality include the amount of sleep, bed comfort, darkness of room, time of day, noise, temperature (cooler is better for sleep) and anything else that interrupts sleep. Sleep debt accumulates. The longer a person has restricted sleep, the greater the increased performance.
Naps are the best antidote to sleepiness. A 20-40 minute nap can greatly increase driver alertness and performance. A 1994 NASA study of airplane pilots showed planned naps reduced dozing by half and errors by a third. Be aware, that sleep inertia follows naps and can disrupt subsequent sleep periods.
Circadian rhythms are daily cycles of physiological occurrences such as hormones and body temperature. Alertness also follows a daily pattern:
Peak performance is after 8am and in the evenings. Least alertness occurs before sunrise and mildly after lunch. Time zone travel affects circadian rhythms. Sleep loss makes the dips in circadian alertness greater. For most people, 16 hours awake is “nature’s Hours-of-Service” rule. A 1997 study showed that being awake more than 17 hours is equivalent to .05% Blood Alcohol Content (BAC) and more than 24 hours is like .10% BAC.
Environmental factors that affect alertness are road conditions, weather, noise, light and social interaction (which can increase alertness while simultaneously distracting).
In a 1996 study, 14% of drivers were identified as high risk drivers with diagnoses of obstructive sleep apnea (OSA), insomnia, and other sleep-related disorders like narcolepsy and restless leg syndrome. The 14% of all drivers who were high risk were responsible for over half of all observed drowsy episodes in the study. Apnea is when a person stops breathing for more than 10 seconds. This is considered OSA if it occurs more than 5 times per hour. This highest risk categories for OSA are obesity, males, 40+ years old, large neck size (17”+ for males; 16”+ for females), recessed chin, small jaw or large overbite and family history. Warning signs include snoring, daytime sleepiness, high blood pressure and diabetes.
It is estimated that 28% of commercial motor vehicle (CMV) drivers have OSA. A 2004 study found a 2x to 7x crash risk for drivers (non-CMV in study) with OSA. Diagnosis occurs through assessment of risk based on criteria discussed above and a sleep study.
To download Module 3, go to http://www.nafmp.org/en/downloads.html.
I am honored that years ago, Dr. William Dement, M.D., Ph.D. of Stanford Sleep Disorders and Research Center, agreed to contribute a chapter to my book Litigating Truck Accident Cases. Dr. Dement is the grandfather of all modern sleep research. Nearly 60 years ago, he coined the phrase “rapid eye movement” or REM. Many of the ideas cited by the NAFMP either comes from the Stanford Sleep Center or finds its roots in the research performed there.
Michael Leizerman is a lawyer and truck safety advocate who has handled truck accident cases in a variety of circumstances, including fatigue and distracted driving.