Welcome to DAT Freight & Analytics’s six-part series on napping, sleep physiology, scheduling, and trip planning. While aimed at truckers in high-risk operating environments, the information will benefit anyone in the logistics industry equally. This week, we’ll explore sleep physiology and how to get better quality sleep from less time in bed.
How much sleep is enough?
The first thing experts will tell you about sleep is that there is no “magic number.” Not only do different age groups need different amounts of sleep, but sleep needs are also individual. Like any other characteristics you are born with, the amount of sleep you need to function best may be different for you than for someone of the same age and gender. While you may be at your absolute best sleeping seven hours a night, someone else may need nine hours to have a happy, productive life.
So, how do you measure how much sleep you truly need? If you have trouble staying alert during boring or monotonous situations when fatigue is often “unmasked,” you probably aren’t getting enough good-quality sleep. Other signs are a tendency to be unreasonably irritable with co-workers, family, or friends and difficulty concentrating or remembering facts. For truckers, it can be as simple as forgetting the last exit.
Have you ever taken a 1-hour nap and woke up feeling worse?
Circadian rhythms, such as the sleep/wake cycle, are relatively well-known, but their ultradian rhythm components are much less understood. A circadian rhythm occurs every 24 hours; an ultradian cycle occurs roughly every 90 minutes. In sleep, our brain cycles through a series of brain wave patterns approximately every 90 minutes, or a sleep cycle.
During that period, a person typically transitions from drowsiness to a lighter stage of sleep before dropping into a deep sleep. The brain then transitions back to a lighter stage of sleep before finishing the sleep cycle with a dream or what’s known as REM (rapid eye movement). It’s known as a sleep cycle and contains all brain wave activity to restore the brain’s ability to function significantly.
Think about a sleep cycle as repairing both physical and mental fatigue – deep sleep fixes the physical (bones, hair, skin, muscles, etc.). Critical functions such as memory, mood, vigilance, and concentration are restored during REM.
So, let’s return to that one-hour nap on a Saturday when you woke feeling worse. The one-hour nap was not refreshing because, at the one-hour mark and in deep sleep mode, your brain is unconscious, but your body is tossing and turning.
When you wake from this stage of sleep, you nearly always wake with what’s known as ‘sleep inertia,’ where you feel groggy, tired, lethargic, moody, and disoriented. If you had let the nap go a little longer to the 90-minute mark, you’d have woken up quickly at the end of the dream because the brain is already awake and buzzing with electricity (from the dream stage of sleep). During REM, your body is in a state of paralysis, so you don’t act out your dreams, but your brain is ready to roll. The same applies to waking before your alarm clock each morning.
You typically wake up at the end of a dream, when you should get out of bed. Hitting the snooze button can take you deep into the next sleep cycle, with the alarm coinciding with deep sleep and the resulting sleep inertia.
Why are six hours of sleep better than seven?
Sleep quality is the ultimate goal, and it comes from the timing of sleep, not so much from the quantity of sleep. In some cases, more hours of sleep can be worse for you. The 90-minute sleep cycle is the basic building block for a good night’s sleep, a series of sleep cycles put back-to-back. Sleep should ideally occur in blocks of 90 minutes, i.e., one sleep cycle equals 1.5 hours, two cycles equal 3 hours, three cycles equal 4.5 hours, and so on.
The timing of sleep, therefore, should be blocks of approximately ninety minutes or 1.5 hours – no part cycles, constantly complete cycles. That’s why six hours or four sleep cycles is better than seven or 4.5 sleep cycles. The extra hour or part of the sleep cycle at the end gives you sleep inertia, resulting in tiredness all day.
Try setting your alarm clock for multiples of 1.5 hours instead of a specific time, add in a few minutes to allow for falling asleep, and see how great you feel!
Disclaimer: This information is not designed to be a substitute for medical advice from a qualified practitioner or a diversion from the safe operation of motor vehicles. If you have any questions about the safe application of this information at your company, please consult your immediate supervisor. If you have health concerns adversely affecting your sleep, please immediately consult your family doctor.