Working Environment And Fatigue Among Fishers in The North Atlantic: A Field Study Part 3

CONCLUSIONS

In this study, sleep efficiency scores from actigraphy ratings on the KSS and PFS were used as outcome variables to examine the association with the work environment.  Hypothesis 1 was confirmed in that engine power correlated positively with sleep efficiency, but was rejected regarding sleepiness and physical fatigue as no relationship was found between the two. Hypothesis 2 was rejected, with no relationship between crew size and the outcome variables. Hypothesis 3 was confirmed, with more ship movement increasing physical fatigue and decreasing sleep efficiency but showing no relationship with KSS. Hypothesis 4 regarding the effect of noise was rejected as noise during time off positively correlated with sleep efficiency and shared no relationship to sleepiness or physical fatigue. Hypothesis 5 about the effect of shift systems was also rejected as no significant impact was revealed between the shift system and any of the outcome variables. Hypothesis 6a was confirmed, with catch-per-person-per-day showing a strong positive relationship with sleep efficiency, while hypothesis  6b was rejected, with no relationship between catch-per-person-per-day and KSS or PFS. Hypotheses 7a and 7b were confirmed, with days at sea having a positive impact on sleep efficiency and an adverse impact on KSS and PFS,   thereby confirming our hypotheses.

Cistanche can act as an anti-fatigue and stamina enhancer, and experimental studies have shown that the decoction of Cistanche tubulosa could effectively protect the liver hepatocytes and endothelial cells damaged in weight-bearing swimming mice, upregulate the expression of NOS3, and promote hepatic glycogen synthesis, thus exerting anti-fatigue efficacy. Phenylethanoid glycoside-rich Cistanche tubulosa extract could significantly reduce the serum creatine kinase, lactate dehydrogenase, and lactate levels, and increase the hemoglobin (HB) and glucose levels in ICR mice, and this could play an anti-fatigue role by decreasing the muscle damage and delaying the lactic acid enrichment for energy storage in mice. Compound Cistanche Tubulosa Tablets significantly prolonged the weight-bearing swimming time, increased the hepatic glycogen reserve, and decreased the serum urea level after exercise in mice, showing its anti-fatigue effect. The decoction of Cistanchis can improve endurance and accelerate the elimination of fatigue in exercising mice, and can also reduce the elevation of serum creatine kinase after load exercise and keep the ultrastructure of skeletal muscle of mice normal after exercise, which indicates that it has the effects of enhancing physical strength and anti-fatigue. Cistanchis also significantly prolonged the survival time of nitrite-poisoned mice and enhanced the tolerance against hypoxia and fatigue.

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We found that the time of day followed by ship movement was the most consistent exposure variable with the highest impact on the outcome variables. It is also noteworthy that the trip length was the only variable that revealed a relationship with all the outcome variables, either as a stand-alone or interacting with the number of sleep periods per day.

Ship variables were found to play a smaller role than expected in the current study. Nevertheless, we will not conclude that these variables don’t matter as the variance between the size of fishing vessels within the same group was rather small, which could account for our findings. Only engine power was strong enough to show a relationship to sleep efficiency and seems to function as a reasonable estimate of the ship’s size. Crew size did not reveal a significant effect. Again, possibly the same applies since there was minimal variation in crew size within the vessel groups and this could be the reason for it.

The trip length in days was a better measure of fatigue than days at sea per year most likely because the number of days per year variable is influenced by more external variables such as the variance in social and work obligations between trips. Neither the shift system nor the number of hours worked per day seemed to have a significant impact on the outcome variables. This finding was unexpected but we believe that it should be included in future studies. Possibly these findings were due 1) to having too small a sample and, 2) the different shift systems most often appearing together (with changes from one vessel type to the other) which, in reality, produce a lot of confounders. When comparing the mean scores on the KSS and physical fatigue, however, we found that the netting vessel crew that worked the longest hours were the ones who scored the highest on the KSS, followed by longliner fresh fish crews who worked the 6-6 system, which has been rated as the worst. The crews on netting vessels also scored highest on the physical fatigue scale; thus, it cannot be rejected that work hours and shift systems do contribute to these scores. The time of day had the greatest impact on both their physical fatigue ratings and sleep efficiency, with the highest sleep efficiency being between  00:30 and 06:30.

The catch in tons per day was revealed to have a positive effect on sleep efficiency while large hauls did not impact the participants’ sleepiness scores or physical fatigue.  We expect the reason behind this to be the psychological processes because their paychecks depend on the catch.  Thus, the more there was to do, the happier the fishers were; and their elevated psychological state combined with the hunting culture (where adrenaline increases when the hunt is good) most likely made them unaware of their tiredness. For these fishers, spending more energy and having peace of mind from knowing that the trip would pay well resulted in better sleep. Higher rankings on the fishers' physical fatigue scale were associated with greater sleep efficiency, unlike higher levels of sleepiness which did not seem to significantly impact it. Only with ship movement do these two outcome variables move in different directions owing to the impact that rolling has on sleep. Even though we did not get significant results from all our exposure variables, we believe that most of them should be included if conducting related studies in the future.

RECOMMENDATION FOR FUTURE STUDIES

Future studies to determine the influence of noise should focus on control groups and individually worn noise meters rather than merely relying on measuring stations. In the current study, we only found significant effects when analyzing it as a single variable against the outcome variables despite the high noise exposures. It was also observed that fishers used earmuffs in the noisiest workstations. Interpreting the result and concluding that noise is not a problem would be a mistake, and most likely a type II error as the high dB(A) noise levels during work and time off exceeded recommendations by the Danish Maritime Authority’s technical regulations which state that the daily personal noise exposure during 12 hours of work should not exceed 83 dB(A).  Maximum exposure in rest areas is set to be 60 dB(A) for bedrooms, 65 dB(A) for leisure rooms, and 65 dB(A) for dining rooms and living spaces. We believe that the explanation for the minimal effects observed is found in the lack of variance as all vessels scored high on noise. Given this, we recommend that researchers in noise-exposed and loud working environments use dosimeters and make comparisons with groups in low-noise-exposed working environments. They should also include a variable that takes into account the wearing of earmuffs and other noise protection gear, and whether or not they are used. We are inclined to believe that the subjective ratings of noise disturbance are reliable, as found by other authors, e.g. Hansen and Holmen  (2011) [17]. The lack of effect found in this study is likely due to the limited variance in noise levels measured by the objective method and the inability to assess and monitor the use of protective aids like earmuffs.

Work environments should be designed to meet human physiological requirements and compensate for their limitations to ensure the well-being and safety of those who work at sea. Our study points to several factors that could be taken into consideration to help move toward this goal. One of the best investments would be to design and construct fishing vessels that would have reduced ship movement. Making a buffer for the increased risk of the circadian nadir by adding an extra person on the bridge during the early morning hours (when the risk of falling asleep is greatest) could improve the safety of the crew and vessel. Additionally, if respite from duties for fishers is possible, we recommend that this be done preferably between the hours of 02:00 to 06:00 to reduce the risk of fatigue and sleepiness which inevitably increase the risk of accidents and other eventualities onboard vessels.

We hope that through this research we succeed in alerting the relevant personnel to further recognize and acknowledge the urgent need to address the health and safety issues that fatigue causes in fishers. Our sincere desire is that this study encourages dialogue on how it is influenced by individual factors and organizational practices. This, we believe, could result in finding more constructive ways to evaluate, manage, prevent, or minimize fatigue and its effects on workers in this vital industry.

Conflict of interest: None declared

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