واکنشهای فیزیولوژیکی به ماهیگیری طولانی مدت در دریای بارنتز Physiological reactions to long-term fishing in the Barents Sea

Introduction Fishing is a potentially risky occupation. This implies an elevated risk of developing cancer, including smokingrelated cancer [1,2], injuries and cardiovascular disease [2,3]. This excess risk may be due to life style factors as suggested by Hjarnoe and Leppin [4]. In line with this, an increased risk of metabolic syndrome has been found among Danish seafarers [5]. Other factors, e.g. shift work, could, however, contribute to this. In the Faroe Islands, the large deep-sea trawlers in distant waters, that is, the Barents Sea, use shift work, mainly 6 h on and 6 h off work, leaving fishermen with 12  h rest, except when the catch is excessive or when equipment is damaged and needs to be repaired. The work is characterized by intermittent high physical demands in cold and rough weather conditions when working on the trawl deck [6]. This alternates with work on the factory deck, which includes operating the headand-cut machine, sorting and cleaning the fish and packing blocks of fish for freezing. The tasks are, however, fixed for each fisherman, and life on board the ship is scheduled and, to a certain extent, predictable [7]. One of the most problematic factors about shift work is that it disrupts circadian rhythms, causing sleep disturbance for many workers [8]. Research has shown that at least 75% of the population working in shifts suffers from sleep disruption [9]. The circadian rhythm is our 24-h body clock located in the hypothalamus region of the brain. In the morning, the hypothalamus increases the amount of cortisol to prepare the body for the activities of the coming day. Burch et al. found higher reports of fatigue and lower mental well-being in shift workers, with lower melatonin levels during sleep and at work [10]. Further, fishermen were found to suffer more from sleepiness when at sea, compared to when ashore (82% compared to 35%) [11]. Fishermen working at sea with a standard working week of 84  h or more may suffer from fatigue. However, Wadsworth et al. found that fishermen adapted to the requirements of life at sea quite quickly, as fatigue increased more slowly after the first week, but that it took the fishermen a full week to recover after returning to land [12].