As a mariner, what do you need to do your job? Depending on whether you’re a master, tankerman, engineer, deck hand, ship pilot, shore tankerman, cook or one of the numerous other maritime positions, there are many responses to this question. A very small percentage, if any, would list sleep. The first part of this article will focus on why sleep is so important to everyone. The second part will focus on the practical aspects of sleep in the maritime industry.
While sleeping, our body rests and restores itself, but our brains are very active. Sleep is an active state that is divided into “stages” and each stage provides particular benefits. The quantity and quality of sleep an individual receives is a determining factor in receiving the benefits of these stages. The level of fatigue, endurance and even health of the mariner are a direct result because, in many ways, both physical health and mental health are affected by sleep.
Sleep – it does a body, and brain, good
Diagram 1, known as sleep architecture, refers to how a person cycles through the sleep stages. This is one of many graphs available and, if researched, others may vary but the stages are similar. Sleep stages are categorized into rapid eye movement (REM) and non-REM (NREM) stages. Most people know that REM sleep is associated with dreaming. Note in the graph that the duration of REM sleep gets longer as the night progresses. Diagram 2 shows the brain waves during each of these stages of sleep. Notice how the brain waves slow down from Stage 1 to Stage 4 (NREM stages) but get very active during REM sleep.
The following are basic descriptions — don’t want to put you to sleep with too much detail — of the five stages of sleep:
NREM 1: Light sleep is the transition from awake to asleep and feels like drifting in and out of sleep. This stage can be accompanied by muscle jerks and the sensation of falling in a dream-like state.
NREM 2: Considered the true beginning of sleep. Within 10 to 15 minutes, brain activity slows further and progresses into the deepest sleep, Stages 3 and 4.
NREM 3 and NREM 4: Termed slow-wave sleep (SWS), see Diagram 2. This is the transition from light to deep sleep. It can be difficult to arouse a person from SWS and, once awake, they may feel sluggish and disoriented for several minutes. Although there is low muscle activity, this is when sleepwalking and sleep-talking is most likely to occur in some individuals.
REM (Stage 5, or Dream Sleep): Characterized by quick eye movements and little to no muscle tone. The skeletal muscles of a person during REM sleep are effectively paralyzed. Also, the heart rate and respiration speed up and become erratic. This stage is most associated with dreaming. When people wake close to the REM stage, they usually note that they were having a very vivid dream. The average person has about 1,460 dreams a year — roughly four dreams per night — but, if awakened during other stages, they normally would report that they weren’t dreaming.
In Diagram 1, note that the sleeper begins in Stage 1, moves through the stages, then back to Stage 1 and then into REM. One cycle, from Stage 1 to REM takes approximately 90 minutes and is repeated throughout the night with the time in REM increasing and time in deep sleep (Stages 3 and 4) decreasing. If you wake up and don’t engage with anyone — no bright lights, no phone/computer, etc. — there’s a good chance you can go back into the stage where you woke up, otherwise you’ll start all over! So if nature wakes you up do your business, don’t look at your phone!
Now for the really interesting part, so wake up! In Stages 3 and 4 hormones are released, triggering functions such as restoring energy, repairing tissues, cell division and growth, regulating appetite and strengthening the immune system. Basically what you physically messed up during your time awake is being repaired. Note that in Diagram 1 you get most of this physical restorative benefit in the first portion of an eight-hour sleep period.
During REM sleep our eyes are active and so are our brains, behaving as if we are awake. Remember that your limbs are temporarily paralyzed. That’s nature’s way to keep us from acting out our dreams. REM sleep is considered to allow the brain to analyze the day’s events, store necessary things to short-term memory, forget unimportant things and allow the brain to work through emotional problems. Note in Diagram 1 that you get most of this cognitive restoration in the second portion of an eight-hour sleep period.
The National Sleep Foundation earlier this year updated its sleep duration recommendations for different age groups — see Diagram 3. Understand that each individual is different physically, mentally and genetically so these recommendations, as well as the above information on stages of sleep, may not apply to everyone exactly as reported. Some adults, even in ideal situations, may not be able to sleep more than six hours — but that may be enough for them. Keep in mind how you feel after getting more or less of your “average” sleep.
Sleep and the mariner
Now that you know why you should sleep and how much sleep you should get, we’ll discuss the sleep issues in the marine industry. Yawn! For the sake of this article I’m going to use the schedule of an individual living on a vessel for 28 days working a square watch — six hours on/six hours off. The information may be applied to your specific work schedule and lifestyle but if after reading this article you’re totally confused or have specific questions about your hitch or schedule, please contact me and we can discuss. My contact information is at the end of the article. Just out of curiosity … did you yawn when you read the word “yawn” in the beginning of this paragraph?
Obviously if you’re off six hours there is no way you’ll get seven to eight hours of uninterrupted sleep, so let’s make sure that the sleep you get is quality sleep. In Diagram 1, note that if you get 3.5 hours of sleep and are able to go through all stages displayed in that time frame, you should feel well physically when you wake up. Remember, Stages 3 and 4 are your physical restoration. It’s the cognitive restoration (REM sleep) you’re lacking. You may not notice the effects right away but after a couple of days, especially later in your hitch, the effects may be more obvious. As time goes on these effects may include issues with decision-making, depression, anxiety and memory, and they may even make you short-tempered. Some crewmembers told me that the third week of a four-week hitch is called “hate week.” Individuals were less social and, let’s say, less tolerant of their fellow crewmembers.
What’s a mariner to do?
First of all, let’s make sure you are getting the most benefit out of the time when you’re asleep. The things that may keep you from getting deep restorative sleep or getting into REM sleep when enough sleep is available, are environmental issues (e.g., noise, temperature, vibration, poor mattress), operational issues (e.g., grinding or soughing the vessel, fleet work movement), personal choices (e.g., heavy meal before bed, nicotine, lack of exercise, too much caffeine or caffeine at the wrong time), stress and even some medications to name some of these risk factors. This is where a risk factor survey, crew endurance plan and education come into play. Not all of these issues can be totally removed, but some may be able to be addressed so your quality of sleep may improve.
What about the cognitive restoration? Although you won’t be able to get through all the cycles of REM sleep, if you can improve your sleep from 3.5 to 4.5 or even 5 hours, you’ll get at least one more longer period of cognitive restoration.
Another challenge for sleep overall is for the back watch — working when their body is designed to be asleep. Your body is in the Red Zone, lowest period of energy, from 2100 to 0700. I’m sure you remember this from one of my previous articles that you printed and saved! Also the body produces melatonin, close to the Red Zone period, to help you sleep. Remember that a certain intensity of bright light, if used correctly, may alter the Red Zone time and melatonin secretion.
Diagram 4 is the biological clock or circadian rhythm of the average individual. Look familiar? Notice how these tasks associated with times (again this is an average) do not always coincide with your work schedule! And we all agree that the mariner lifestyle is more difficult sleep-wise for the night watch. There are more risk factors and higher potential for accidents and health issues. Education and personal choices play a major role in being able to work this watch and still get good quality sleep, maintain good health and work safely.
For both watches, a countermeasure to not getting enough cognitive restoration is napping. A nap is considered a sleep period of less than two hours. There are different types of naps. On your six hours off where you don’t get your main (or anchor) sleep, if you can sleep for 90 minutes you have the opportunity to go through a full cycle of sleep and avoid the grogginess that you may have when waking up in a deep stage. When possible, use your main sleep period to get as much sleep and as many sleep stages as possible. Utilize your other off period to do personal chores, communicate with family and friends, socialize, exercise and get a nap when you need it.
Keep the sleep architecture in mind when you’re at home on your off time also. Being well rested and alert when you come to work plays a role in your level of endurance as you work through your hitch. Stay safe.
Jo Ann Salyers is an independent consultant and owner of Salyers Solutions LLC, with 35 years in the safety, training and risk management areas of the maritime industry. Jo Ann is a certified USCG CEMS Expert and holds CEMS Coaches and Awareness sessions throughout the country. Visit http://salyerssolutions.com or e-mail: firstname.lastname@example.org, or phone (504) 236-4962.