Saliva cortisol level as a strain parameter for crews aboard merchant ships

Seafarers working in maritime settings are affected by a great number of psychosocial stressors. The testing of cortisol in saliva is a well-established method for judging the individual strain. Therefore, this study aims to assess the crews' strain on container ships on the basis of this parameter, taking occupational groups and the three voyage episodes of the vessel into account (stay at port, river passage and sea passage). One scientist accompanied 22 sea voyages and examined 304 crew members who had provided a minimum of 5 saliva samples from at least one day. Altogether, 4,073 saliva samples were collected. An evaluation of stress hormones was conducted by analyzing on the basis of groups and day profiles. The present study revealed that the average concentration of cortisol in the saliva of the examined seafarers was lower during the first hour after waking up than that of a healthy reference population. There were significant differences in the cortisol between nautical officers, deck ratings, and engine room personnel with decreasing levels (p < .001). Furthermore, the highest cortisol level was measured during port stay followed by sea passages and river passages (p = .002). After adjustment, the average level of cortisol in saliva of the whole study group was positively associated with acute shipboard stressors, namely the average current working time (p = .050) and the average number of terminals that had been served during the last 7 days (p = .008). In contrast, no association of saliva cortisol was observed with age (p = .130), smoking status (p = .436), the current stay on board of the vessel (p = .230) or with the subjective stress evoked by noise, vibration, ship motion or psychophysical demands on board. Only the deck ratings and the engine room personnel displayed a continuous decrease in the cortisol level in the daily profile (p < .001). In total, the present study revealed an association of the saliva cortisol level among the examined crew with acute shipboard stressors, the working group, and the ship's voyage episode. A reliable collection of samples over several days on board is well possible through the presence of a specially trained person on site. In maritime studies, this high level of personal effort seems to be inevitable in order to allow a differentiated judgement of the hormone stress reaction of seafarers and meet high quality standards.