## 2 Seafarer Fatigue, Sleep and Ship Noise
### Seafarers' Fatigue and Sleep  
The pooled data from a study revealed a substantial prevalence of fatigue among seafarers, with an average prevalence rate of 65%. Notably, the prevalence varied across different maritime sectors, ranging from 50% to 80% [25]. The analysis of contributing factors indicated that long working hours were a significant driver of fatigue among seafarers. The data showed that seafarers working more than 12 h per day had a 1.5-fold higher risk of experiencing fatigue compared to those with shorter work shifts. Additionally, demanding schedules, such as consecutive days of work without adequate rest, were found to increase the likelihood of fatigue among seafarers by 1.8 fold [26]. Extended periods away from home, a characteristic of seafaring occupations, also emerged as a substantial contributing factor to fatigue. Seafarers spending more than 6 months continuously at sea were found to have a 2.3-fold higher risk of experiencing fatigue compared to those with shorter durations [27]. Fatigued seafarers consistently exhibited decreased alertness, with studies reporting an average decrease of 30% in alertness levels compared to well-rested counterparts [28]. Cognitive function was also significantly impaired, with fatigue leading to an average decline of 25% in cognitive performance metrics such as memory, attention, and reaction time [29]. Furthermore, seafarers experiencing fatigue demonstrated reduced situational awareness, with a decrease of 35% in the ability to accurately perceive and comprehend critical information in their surroundings [30]. This decline in situational awareness poses substantial risks to maritime safety, as it hinders timely detection and response to potential hazards. Moreover, the compromised decision-making abilities of fatigued seafarers were evident in the numerical data. Studies indicated a 40% decrease in the quality of decision-making processes among fatigued individuals, including impaired judgment, decreased problem-solving abilities, and a higher likelihood of making errors or poor choices [31]. The numerical data indicated a high prevalence of irregular sleep patterns among seafarers, with approximately 75% reporting disrupted sleep schedules due to their work demands and shift rotations. Environmental factors, such as noise and vibration, significantly contributed to disrupted sleep among seafarers. The data showed that noise levels exceeding recommended thresholds were reported by over 60% of seafarers, leading to frequent awakenings and reduced sleep quality. Moreover, the inadequate onboard accommodation facilities, as evidenced by research, affected sleep quality for approximately 80% of seafarers, with limited space, uncomfortable beds, and poor ventilation being the primary factors [32]. [PERSON] et al. researched a longitudinal study on fatigue and health disorders among seafarers. The study aimed to investigate the relationship between fatigue and various health issues in this occupational group. The findings indicated that seafarers' fatigue was associated with an increased risk of health disorders. These health disorders included elevated stress levels, depression, anxiety, cardiovascular problems, and musculoskeletal disorders. The study stresses out the importance of addressing fatigue management and promoting better health outcomes for seafarers in the occupational health and safety context. Seafarers' fatigue and insufficient sleep have been linked to various health issues, including increased stress levels, depression, anxiety, cardiovascular problems, and musculoskeletal disorders [33]. [PERSON] et al. conducted a study using the white hall II cohort to examine the relationship between sleep duration, sleep quality, and future sickness absence. The study aimed to determine whether inadequate sleep predicts increased sickness absence in the future. The findings revealed that both shorter sleep duration and poor sleep quality were associated with a higher risk of future sickness absence.