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The importance of sleep in our 24-hour routine is unquestionable. It is often simplified to a time frame, within which we fall asleep, thus hopefully rest so we can have another effective day. There is however, a lot more to sleep than just a lull time period, when little else but rest gets accomplished. Sleep science has evolved over the last 7 decades or so, into an elaborate research that is hoping to explain a number of human ailments. In this article however, the main focus is on sleep and how it relates to our performance. Performance not necessarily viewed as a simple OPH (output per hour), but rather a self-conscious and safe state of personal alertness. In turn, it directly relates to our state of fatigue, thus influencing are judgment and ability to respond in an effective and responsible way.

The marine industry, and shipboard work especially, imposes a number of unique challenges, that few of the others do. It is a constant flow of tasks that must be performed 24 hours a day, 365 days a year. It does not differentiate a week day from a holiday, it knows of no breaks or special rest periods, it implies a work environment with a never ending need for readiness.

Fatigue has been linked to majority of human error based accidents. USCG has officially released data that connects 80% of all marine accidents to a human factor. Whether this was due to a fatigue or an incompetence is for another discussion.

Sleep is a complex function of the human body.

  • sleep_studies

Below is a brief caption from the University of Vanderbilt research project on Inclusion of Fatigue Effects in Human Reliability Analysis:

Fatigue degrades human performance.The degree to which fatigue affects an individual can range from slight to catastrophic. Unlike alcohol or drugs which can be detected by biochemical tests, fatigue is more difficult to prove as a cause of accidents – typically fatigue must be inferred from the context of the situation. Fatigue is a personal experience, a function of the individual’s aspirations, achievements, self-evaluations and present and previous circumstances. Despite this limitation, increasingly, fatigue has been claimed as the primary cause of many major accidents. For example the incidents of Bhopal, Exxon Valdez, TMI, and Chernobyl list fatigue as a root cause.

Seamen are faced with numerous challenges just to overcome the basic need for sleep (rest). This is especially evident in a short trip operations (like on coastal routes) where time-off vs. time-on (as it applies to work and rest time) has been cut to minimum. It is also a common belief (evidenced more than one should care to admit), that while illegal, a refusal to work past assigned hours is going to result, sooner or later, in an employment termination. This additionally compounds the problem, as if insufficient rest wasn't enough.


The study and research on sleep had not started on a larger scale until brain activity monitoring equipment was put into use. Sleep stages were originally described in 1937 as being 5 stages from wakefulness to deep sleep, all 5 then recognised as NREM type (or non-rapid-eye-movement). Year 1953 brought in the discovery of REM stage, or rapid-eye-movement, and the sleep was reassessed as consisting of 4 stages of NREM followed by an REM. Sleep science is currently governed by AASM (American Academy of Sleep Medicine) standards issued in 2007 and break down human sleep cycle into 4 stages: N1-N2-N3-REM. and a typical sleep cycle flows like this

N1 - N2 - N3 - N2 - REM

  • sleep_stages_thru_night

Stages N1, N2, N3 are NREM type, but each is somewhat different.

  • N1 - reduction in activity between wakefulness and stage 1 sleep, eyes are closed during N 1, one can be awakened without difficulty, however, if aroused from this stage of sleep, a person may feel as if he or she has not slept. N 1 may last for five to 10 minutes, many may notice the feeling of falling during this stage of sleep, which may cause a sudden muscle contraction (called hypnic myoclonia).
  • N2 - a period of light sleep during which polysomnographic readings show intermittent peaks and valleys, or positive and negative waves, these waves indicate spontaneous periods of muscle tone mixed with periods of muscle relaxation, the heart rate slows and the body temperature decreases, at this point, the body prepares to enter deep sleep.
  • N3 - deep sleep stage known as slow-wave, or delta, sleep, if aroused from sleep during these stages, a person may feel disoriented for a few minutes.
  • REM - typically occurs some 90 minutes into sleep cycle, eyes move rapidly in different directions, brain activity is increased yet muscles remain immobile, intense dreaming takes place during this stage, length of REM period differs an increases in length as it re-occurs in succeeding cycles from some 10 minutes to 60 minutes towards morning (or last cycle), it is recognised that REM is quite long for infants (some 50% of their sleep is in REM mode) and drops to 20% of total sleep time in adults.

A single cycle comprised of above stages lasts from 90 to 120 minutes, then it flows right back into N1 and the next cycle begins. Cycles loop through 4 to 5 times in a single night, with small yet distinct differences from one cycle to the next, especially the REM increases in length as the sleep progresses.

  • MNZ_biological_sleep_drivers_1
  • MNZ_sleep_cycles_1

It can easily be seen now, that sleep is a complex process. If interrupted, can lead to major rest / fatigue issues. This is unfortunately, what a mariner must deal with on a daily basis. His sleep is often cut into short periods, worse though, these interruptions are of unpredictable patterns and lengths. This is especially the case on frequent dock changes and vessel movements, but even vessels on long routes, such as LNG or VLCC etc, run into the same problem while in port, just when alertness and fresh mind is needed for safe cargo operations (the only positive being relative short port stays for such vessels). In practical terms, it is impossible to address mariner's sleep problems to meet scientific criteria of adequate rest. We must therefore recognise it and accommodate as best we can. This imparts a demand for a better corporate & social responsibility.

Let's go back to sleep again and how we can best take advantage of what we now know. As all mariners are now aware, once the industry admitted lack of rest and thus fatigue, as one of the major contributing components of unsafe practices, an STCW work hour scheme was implemented. To this day though, there is continued confusion as to what STCW hours mean and how they relate to attaining the best possible rest. Here is what CFR states on work / rest hours:

  • rest_hours_per_CFR

Clearly, CFR is not completely up to the task. It does explain the break down for required rest periods, but is off the mark by the inclusion of DRILL in (c) without ANY underlying extensions. While drills need to be performed on a regular basis, they are often misconstrued as an actual emergency (which they are not), instead of being viewed as additional work hours that cut into ones' rest period. It is not unusual to see a zero consideration given to the impact a drill may have, held on a given day at a specific time,  on personnel. The solution to this is simple enough. There should be a clause added, that clearly recognises drills as work hours and the actual circumstances must be taken into consideration prior to announcing a drill. As it's stated, we allow for uncontrolled calls. One of the related problems is, that while international maritime community, IMO included, has long recognised the need to cut back on actual emergency drills to ONE per month (augmented by weekly safety & training sessions), there is still a number of ship operators that do not subscribe to it, with continued insistence on weekly events. There is however, a far more important root cause.

While STCW convention has addressed the work vs. rest topic to some extent, it did NOTHING to affect changes in vessel manning requirements. Call it a catch 22 if you will, but what good does regulating of work hours do, if the same "authority" allows for a major under supply of man power (I use "allow" loosely, STCW is mum about manning levels) . For whatever reason, it appears that depending on vessel size or trading routes, one can be operated with half the crew versus the other. If an authority believes that a certain type of vessel does not need a full complement of personnel, then it should follow its operations and see how they actually differ from the implied model.

Ship manning must be addressed to at least the same extent as the work hours, or we're basically refusing to face the truth. A tanker, while a better media target in a pollution accident, should not be any different in manning levels than a car carrier or a bulker. New technology now available (and soon to be required) for bridge watch keeping does NOT decrease the need for a well rested and competent watch standers. If anything, it does quite the opposite.

Back to sleep and fatigue. A subject of sleep accumulation sometimes pops up in discussions. Is it actually possible to either  oversleep beforehand in order to "store" rest energy for later "release" when we're called to perform beyond typical uninterrupted hours? Or is it possible to follow a long day with an extra long sleep period in order to regain a state of biological balance? In general the answer to both is NO.

Circadian rhythm is our biological clock that continues to tick, regardless of what we do. Under normal circumstances it is quite closely connected to times of light and dark and so we sleep at night and move about during the day. It can be altered, if our daily routine throws us into an odd pattern for an extended period. In case of a mariner, some watch keeping positions require a night work, which is obviously in conflict with a typical rhythm. Over time our body can adjust to this new cycle and allows us to deal with  it in a more predictable way. The problem here is though, that we must strive for a day-to-day repeatability, so biological adjustments meet at similar times. Such need must be recognised by the vessel's management and taken into account when scheduling tasks for such individuals. This diagram (provided by Wikimedia on-line repository) shows a typical human biological clock.

  • biological_clock

Our body would like to work this way, but we're routinely faced with issues like stress, fatigue, state of mind etc. that play an important part in our body's responses. In effect, we can view this diagram as a model, that may not necessarily fit ours. Never the less, the main aspect of providing an even and predictable work schedule remains intact. This also directly connects with the earlier point for a needed improved corporate and social responsibility.

Social responsibility

A mariner should not have to be reminded that live-aboard / work-aboard poses additional challenges on everyone involved and nothing should be done to make it even worse. Shipboard lifestyle combines a relatively large group of (often estranged) people, who live and work in a confined environment. It is easy to forget about who is on the other side of a bulkhead. What may appeal to us, may well be a major throw-off for the others. Living in such an environment does not leave us with choices we make for ourselves, we must make them in tune with the others. We may not like it, yet there is no choice, but communicate the differences. The same of course, applies to the often seen strong personal aversions to other crew members. If we can't controll it, we should be looking for another job. Live-and-work-aboard is a demanding undertaking and some of us simply don't fit into it. It is quite common, for example, to see how political beliefs can affect personal relations. If you're affected by it, stop participating in such discussions. While many can simply "respectfully" disagree and carry on, some can't stop thinking about it long after it's over. In turn their state of mind is moving further away from a relaxed state, which drastically changes sleep efficiency. In other words, if you seem to be doing a lot of past-day related "thinking" at bed time, you should look into making changes to how you go about work and social realtions as a whole.

Corporate responsibility

In this late 2009, the industry has become a constantly vetted workplace, additionally stressed by the always possible environmental impact it may impose on a locality. Contrary to the corporate belief, there is no such thing as a safe cargo operation covering a vetting inspection and COI all at the same time. On top of that, let's throw in a major provisions delivery and a contracted maintenance.

How about being flown across the world to meet the ship? How often have we been placed aboard, given no time to relieve the watch, then be forced to stand a bridge watch? All of it after a 30 + hour flight in a super duty economy class seat? Fankfully, this has been adequately addressed by some ship operators, but there is no rules that are linked to it, and no recommendations either. Feel lucky, if your employer has been regularly putting you in a hotel prior to joining a vessel.

Corners have to be cut somewhere to make it all possible. We live through it, we deal with it, we survive it time  and again. We must be waiting for an accident to occur that will be clearly rooted to such an undertaking, before some new regulation will try to change the playing field. Where is the STCW hours, need for rest and relaxation? There must be a better way to satisfy the need to inspect, with the need to do it in a safe manner. It's happening because we do it, keep quiet and then do it again. Actually, we don't exactly keep quiet, we just complain within ourselves, which only adds to the stress. At any rate however, none of it is good for creating and maintaining a safe and efficient work place.

Eat or Not to eat? Drink or Not to drink? That is the question

Just a few years ago, I never even thought of how my eating habits play into my rest or sleep periods, or how my body can be affected by a drink or a snack just before the bed time. Turns out, they could quite significantly. While some pro "dietitians" try to disprove of such an advice, it is common to experience digestion problems, if eating/drinking inappropriately before sleep. A lot depends on other health conditions of an individual. This article is not about giving a health advice.

In general, it is advised to stop food intake about 2 hours before bed time, although fruit should be fine (cookies? NOT!). Same goes for large liquid intake, then again a glass of water might help. Some seem to think that a sparkling water is actually even better for bed time. Some people experience long and odd dreams when they eat before sleep, others feel a lot less rested after such night. The list goes on. In any case however, the most important thing is to be aware of what eating and / or drinking before going to bed might do to your rest. As many things in life, not every organism will respond to late food /drink in  the same way. But do remember, that metabolism does slow down during sleep.

Now, how does the above tie into a mariner's work day?

We all know how erratic our day aboard can be. There is hardly any way to predict what's next. Yet, we should always make the best of it. Trying to stop eating 2 hours before sleep is just about impossible, so forget it. Yet, do keep in mind that a heavy food or drink intake before bed is not going to help getting the best rest possible. Large amounts of liquid intake leads to mid-sleep head calls (yes, our body is smart to wake us up for a decant). It is also a know fact, that alcohol does no good to helping us rest. It is a so-called alcohol induced sleep, that leads to interrupted and short sleep patterns with often associated head aches and other related pains.

Information is out there

It appears that there is an internationally sponsored consensus on the impact of fatigue in human induced accidents. Yet, as one looks through the various approaches maritime nations have undertaken to address it, there seems to be a disconnect between legislative and implementative aspects. Some have decided to rest on the regulations, others have gone beyond and invested on the informative front. While having good looking posters all over the work place won't do much good, if at the same time no leeway is given to address fatigue in real time, an effective informational campaign is critical.

Here is a page from what Maritime New Zealand has published on fatigue.  A complete folder can be downloaded from a link at the bottom of this article.

  • MNZ_safety_risk

It is indeed a well known fact, that for any campaign to be effective, it must be concise and easily sighted. This is a great implementation of both principles.

The (in)conclusive bottom line

Mariner is known for dealing with what he's given. It is a hate or love relationship. Many would never even consider taking on a shipboard job, had they known its challenges, demands, stressfulness, separation from a normal life style, and (often) grotesque shortcomings. Some of us get credit, some never do, but in general it is a rewarding experience, if we decide to make it so. That aside however, it is often up to the mariner to help make it better and safer. Fatigue is integral to being part of it, and it is up to the mariner to understand what it is, how to recognise it, and how to minimise it. So long as our focus is on creating a safe working place and we manage to communicate about it effectively, we're going to manage the risks successfully. A safe place is also an effective one.

When it comes to sleep, rest and fatigue, remember at least these few points:

  • if you feel tired or your judgment seems impaired, tell the supervisor or department head
  • if you have not had slept in more then 16 hours, ask for time off, even if you feel like you can go on for another day without rest
  • if there is anything that makes you uncomfortable or cuts into your rest, speak up, others might not even be aware of you being affected by it
  • you cannot make up for a lost sleep, plan your rest periods and daily routines accordingly
  • you cannot accumulate sleep time for a later "release", sleeping too long will have a negative  effect on your judgment or behavior, and you may pose just as bad a hazard
  • performing too many tasks at the same time adds stress and worsens fatigue
  • each individual has different needs in order to rest and relax, do what works best for you, yet don't forget about your shipmate who may not always appreciate it


Maritime New Zealand - development of fatigue management programme

Maritime New Zealand sleep & fatigue posters

Wheelhouse fatigue checklist



Last Updated (Wednesday, 24 July 2013 03:57)

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