Lifestyle factors in Croatian seafarers as relating to health and stress on board

Abstract

BACKGROUND: Seafaring is characterized by specific stressors and health risks.

OBJECTIVE: The purpose of this article was to compare the prevalence of various lifestyle factors between the shipping and home environments, and in addition to test the relations between lifestyle factors, perceived stress on board, and health in seafarers.

METHODS: A total of 530 Croatian seafarers participated in an on-line survey. The questionnaire contained requests for demographic data and a set of questions relating to lifestyle, stress on board, physical health symptoms, and mental health.

RESULTS: The data showed higher sleep deprivation, higher levels of smoking and unhealthier diet at sea than at home, with prevalence of alcohol consumption and physical exercise being more favourable for the shipping environment. Sleep deprivation, unhealthy diet, lack of physical exercise, and smoking are shown as negative correlates of various measures of health. Stress on board was associated with sleep deprivation and unhealthy diet, and with more unfavourable physical and mental health.

CONCLUSIONS: The results give practical implications for promoting health in seafarers. Some of the lifestyle factors tested, such as alcohol use, smoking and physical exercise, fall rather under individual control, but others, such as a healthy, balanced diet on board and sleeping hygiene at sea, should be improved by shipping management.

Keywords

Stress on board mental health gastrointestinal symptoms cardiovascular symptoms unhealthy lifestyle

1 Introduction

The decline in the number of seafarers from developed countries and the consequent increase in the number of seafarers from developing countries, which also results from a desire to reduce labour costs [1], show that seafaring has become a less attractive profession in developed countries in recent years [2]. Globalization of the shipping industry, increased automation and mechanization of work on ships, improvements in navigation techniques, reduction in crew numbers, increased uncertainty and short-term contracting of seafarers in commercial fleets, multicultural crewing, and ships operated under flags of convenience [3] are recognised as major changes within the last three decades which may influence the health of seafarers.

In spite of many advances in the modern maritime sector, seafaring is still characterized by specific risks and stressors which may diminish the seafarers’ safety and physical and mental health. Seafaring risks include 1) accidents due to harmful conditions at sea and to non-observance of safety rules, 2) piracy, the incidence of which has been rising since the mid-1990s, 3) risk of communicable diseases, including those related to on-board hygiene, 4) the limited ability to provide medical aid on board, which is most pronounced in cases of heart failure, and 5) exposure to hazardous substances and UV light, which may be related to the risk of occupational cancer [4 –8].

Previous studies have indicated a large number of stressors that seafarers face. These may be categorized as psychosocial, environmental, and work-related stressors. The most-cited psychosocial stressors in seafaring are: long-term separation from home and family [5 , 9–11], loneliness and social isolation [3 , 10]. Life on board brings with it additional stressors related to deprivation of physical and psycho-social needs, whereby limited opportunities for recreation and social events impair seafarers’ physical, psychological and social well-being [6, 10]. Environmental stressors on board include poor weather, ship motion, noise and vibration, and heat [6 , 12]. Work-related stressors in seafaring include the demands of the job – high workload and, especially, long working hours [13], which lead to fatigue [14 –17], the level of control seafarers have over their work [18] and role conflict resulting from conflicting work demands [19]. Furthermore, the support received from management and colleagues, the seafarer’s role in the organization, change and change management, job security and relationships at work [5] are also regarded as work-related sources of stress in seafaring, wherein multinational crews are recognized as a specific stressor [5 , 10]. Some seafarers report exploitation and abuse [5], which is most evident in those seafarers who work in a substandard sector of merchant shipping. Seafarers also report the “criminalization of seafarers” as one special source of stress, which relates to the denial of procedural and human rights in the investigation and prosecution of maritime incidents [5].

Studies relating to health, morbidity and mortality in seafarers (e.g. gastrointestinal and cardiovascular disease mortality [20, 21]) are often confounded by the ‘healthy-worker effect’, which is explained by self-selection and adaptation. Seafarers who cannot adapt to work on board, as well as those who are suffering from the effects of occupational stressors, leave the occupation. Still, Oldenburg et al. [7] show that, after taking into consideration the healthy-worker effect of seafarers, cardiac risk factors occur slightly more frequently in seafarers than in the general population. Furthermore, the data of suicides in seafarers [5] have shown that the mental health of seafarers in many cases continues to be very poor and often fatal.

Besides stress on board, mortality and disease in seafarers may be largely explained by unhealthy lifestyle factors, such as smoking, alcohol consumption, malnutrition (unbalanced, high-fat diet), lack of physical activity, and obesity [22 –29]. However, the important question which poses itself here is: Are the unhealthy life-style factors seen in seafarers the result of a stressful working life (maladaptive way of coping with stress), or do people with a specific life-style incline more towards this occupation? Our study does not aim to answer this question: only to give some insight into its complexity, since common impacts of working conditions and individual life-style factors are assumed. Our research had two main objectives:

To compare prevalence of lifestyle factors between home and ship environments, i.e. test the hypothesis that the shipping environment encourages various unhealthy lifestyle factors, so the prevalence of unhealthy factors will be higher at sea than at home (H1).

To test relations between perceived stress on board, lifestyle factors and physical and mental health in seafarers.

On the basis of the previously-mentioned research in seafarers [e.g. 28], we expected that unhealthy lifestyle factors would be related to lower levels of various aspects of physical health, for which we used cardiovascular, gastrointestinal and musculoskeletal symptoms (H2-1). In accordance with research in other populations [30, 31], we expected that unhealthy lifestyle factors would also be related to lower levels of mental health in seafarers (H2-2).

Furthermore, we tested the major assumptions of different occupational-stress models [32 –34] regarding links between stress and health, and therein we expected that higher levels of stress perception on board would be related to lower levels of both physical and mental health (H3).

Finally, if seafarers are prone to bad habits as a result of maladaptive strategies of coping with stress, then a relation between unhealthy lifestyle factors on board and higher levels of stress might be expected (H4).

2 Method

2.1 Ethics

The study was approved by the Ethics Committee of the Department of Psychology, University of Zadar. Participation in the study was voluntary, and participants were informed about all important aspects of the study in the invitation letter. Confidentiality of data, anonymity of participants, and feedback on the results of the study, to participants on request, were guaranteed. The data collected did not include any names or contact details, or names of shipping companies in which participants are employed. The participants had opportunities to contact a researcher with questions or comments, via e-mail or telephone number.

2.2 Procedure

The study was conducted in 2014 using an online survey. In order to reach Croatian seafarers in international seafaring, we contacted various organisations and groups with a request to help us with sampling. We contacted Croatian agencies for seafarers, Croatian shipping companies, the Seafarers Union of Croatia, various education institutions in Croatia involved in the training of seafarers, and various groups of Croatian seafarers which have a public page on the internet. Associates from these organisations forwarded our invitations for participation, accompanied with a link to the survey, to seafarers related to their organisations via e-mail, and/or advertised our study on their web-pages. Unfortunately, the sampling procedure used does not allow us to give data on response rate. At the time of the survey, 39% of the participants were on board, and 61% at home.

2.3 Participants

The study included 530 Croatian seafarers employed in international shipping. The average age of the participants was 37.7 years (SD = 9.5), and length of service in the maritime sector 13.5 years (SD = 9.4). Officers and engineers comprised most of the respondents (85.5%). These included deck officers (36.7%), engine officers (22.8%), commanders (16.4%), chief engineers (9.6%), electricians (6.6%), trainees (3.2%), deck ratings (3.2%), engine ratings (1.5%), and catering/steward staff (0.9%). The largest number of participants worked on LNG and LPG ships (27.1%), oil tankers and oil products (17.3%), and containers (17.1%), while the remainder of the sample worked on ships for the transportation of chemicals, bulk cargo, cargo on wheels, general cargo and other ships. Most participants were married (66.7%), followed by unmarried (21.8%), in domestic partnership (9.2%), divorced (1.7%) and widowed (0.6%). About two-thirds of the participants (63.2%) had children.

2.4 Materials

The questionnaire included questions about age, years of service, job description, type of ship, marital status, children and current location.

Lifestyle factors were measured with a set of questions relating to: smoking (number of cigarettes per day), use of alcohol (frequency and quantity, where quantity was measured as the number of standardized units of alcohol per day in a typical day when drinking), sleeping (number of sleeping hours in an average day), physical exercise (frequency), and healthy balanced diet (self-rated frequency). Subjects rated their habits in two situations, at sea and at home, with regard to their “typical behaviour”. Response options for each question are shown in Table 1.

Table 1
Comparison between on-board and at-home habits of smoking, alcohol use, sleeping, physical exercise, and healthy balanced diet (N = 530)

On board At home Chi-Square¹ (df)

N % N %

Smoking (cigarettes / day) 0 307 57.92 309 58.30 28.77^* (4)

⩽5 32 6.04 49 9.25

⩽20 94 17.74 106 20.00

20–30 62 11.70 49 9.25

>30 35 6.60 17 3.21

Alcohol frequency (average) Never 236 44.53 38 7.17 1159.60^* (4)

⩽1×per month 129 24.34 109 20.57

⩽1×per week 70 13.21 159 30.00

2–3×per week 49 9.25 109 20.57

⩽1×per day 46 8.68 115 21.70

Alcohol quantity (standard drink unit³ / day) 0 309 58.30 128 24.15 348.13^* (5)

1–2 167 31.51 247 46.60

3–4 37 6.98 104 19.62

5–6 11 2.08 28 5.28

7–9 2 0.38 12 2.26

>9 4 0.75 11 2.08

Sleeping (hours / day) <5 21 3.96 3 0.57 1574.68^* (5)²

5 52 9.81 1 0.19

6 160 30.19 50 9.43

7 181 34.15 151 28.49

8 87 16.42 224 42.26

9 25 4.72 68 12.83

10 4 0.75 30 5.66

>10 0 3.96 3 0.57

Physical exercise programme (45–60 minutes) Never 142 26.79 157 29.62 21.75^* (4)

2–3×per month 125 23.58 147 27.74

1×per week 20 3.77 31 5.85

2–3×per week 166 31.32 139 26.23

Every day 77 14.53 56 10.57

Healthy, balanced diet Never 46 8.68 4 0.75 1227.49^* (3)

Rarely 240 45.28 53 10.00

Often 186 35.09 278 52.45

Always 58 10.94 195 36.79

		On board	At home	Chi-Square¹ (df)
Smoking (cigarettes / day)	0	307	57.92	309	58.30	28.77^*** (4)
	⩽5	32	6.04	49	9.25
	⩽20	94	17.74	106	20.00
	20–30	62	11.70	49	9.25
	>30	35	6.60	17	3.21
Alcohol frequency (average)	Never	236	44.53	38	7.17	1159.60^*** (4)
	⩽1×per month	129	24.34	109	20.57
	⩽1×per week	70	13.21	159	30.00
	2–3×per week	49	9.25	109	20.57
	⩽1×per day	46	8.68	115	21.70
Alcohol quantity (standard drink unit³ / day)	0	309	58.30	128	24.15	348.13^*** (5)
	1–2	167	31.51	247	46.60
	3–4	37	6.98	104	19.62
	5–6	11	2.08	28	5.28
	7–9	2	0.38	12	2.26
	>9	4	0.75	11	2.08
Sleeping (hours / day)	<5	21	3.96	3	0.57	1574.68^*** (5)²
	5	52	9.81	1	0.19
	6	160	30.19	50	9.43
	7	181	34.15	151	28.49
	8	87	16.42	224	42.26
	9	25	4.72	68	12.83
	10	4	0.75	30	5.66
	>10	0	3.96	3	0.57
Physical exercise programme (45–60 minutes)	Never	142	26.79	157	29.62	21.75^*** (4)
	2–3×per month	125	23.58	147	27.74
	1×per week	20	3.77	31	5.85
	2–3×per week	166	31.32	139	26.23
	Every day	77	14.53	56	10.57
Healthy, balanced diet	Never	46	8.68	4	0.75	1227.49^*** (3)
	Rarely	240	45.28	53	10.00
	Often	186	35.09	278	52.45
	Always	58	10.94	195	36.79

Note: ¹Frequencies obtained for the on-board situation were compared to at-home data as theoretical frequencies. ²For the analysis, the following cells for categories of sleeping were merged: ‘<5’ with ‘5’, and ‘10’ with ‘>10’. ³The standard drink unit was defined as 1 beer (330 ml), 1 glass of wine (140 ml) or 1 measure of a spirit (40 ml). ^***p < 0.001.

Stress on board was measured with a newly-developed instrument consisting of 16 items (all shown in Table 2). The items were based on a detailed literature review of the main stressors in seafarers [e.g. 5, 6, 10, 11, 15, 18, 19]. Respondents were instructed to evaluate each potential source of stress according to its stressfulness for them personally within the period of the last year. They gave their ratings for each item on a 5-point scale (1 = not at all, 2 = mostly not, 3 = neither no nor yes (moderately), 4 = mostly, and 5 = completely). The exploratory factor analysis performed (maximum likelihood factors) showed a one-factor solution, and explained about 38% of the variance. All items had satisfactory factor loadings (see Table 2).

Table 2

Summary of EFA on ‘Stress on Board’ scale results

Items	Factor loadings
Long-term separation from home	0.38
Loneliness and social isolation	0.50
High workload	0.59
Long working hours	0.63
Low level of control over work	0.74
Lack of support from management and/or colleagues	0.75
Social relations at work	0.70
(Un)importance of my role in the shipping organization	0.64
Changes in the work and the way of managing change	0.72
Conflicting work demands	0.74
Multinational crew	0.46
Environmental stressors on board (e.g. noise, vibration, ship motion)	0.56
Exploitation and abuse	0.58
Limited opportunities for physical exercise and social activities	0.63
Job insecurity	0.61
Treatment of maritime incidents as crimes	0.53
Eigenvalue	0 6.10
% of variance explained	0 38.16

Mental health was measured by a five-item version of the Mental Health Inventory (MHI-5) [35], which assesses various domains of mental health: anxiety, depression, general positive affect, and behavioural/emotional control. Respondents give their answers on a 6-point scale (from 1 = all the time to 6 = never). Example of item: ‘How much of the time during the last month have you been a very nervous or anxious person?’ (recoded item). A higher score on this scale indicates better overall mental health.

Gastrointestinal symptoms, cardiovascular symptoms and musculoskeletal symptoms were measured by three subscales of the Physical Health Questionnaire section of the Shiftwork Survey, which was developed as a shorter version of the Standard Shiftwork Index. The subscales for gastrointestinal and cardiovascular symptoms consist of 8 questions each, while the musculoskeletal-symptoms subscale consists of four items. Response options range from 1 = almost never to 4 = almost always. Examples of items: ‘How often do you suffer from constipation or diarrhoea?’ (gastrointestinal symptom); ‘Have you ever been aware of your heart beating irregularly?’ (cardiovascular symptoms); ‘How often do you suffer from pain in your shoulder and/or neck?’ (musculoskeletal symptom). A total score is computed for each scale by summing the individual scores, and a higher score on each scale is associated with poorer physical health.

Alpha coefficients, which ranged from 0.82 to 0.90, indicated good internal consistency for all scales used (Table 3).

Table 3

Descriptive statistics for stress perception, gastrointestinal, cardiovascular and musculoskeletal symptoms, and mental health (N = 530)

Scale	Cronbach	Range	Theoretical	M	SD	Median	Interquartile	Skewness	Kurtosis
(number of items;	alpha		range				range	(SE)	(SE)
scale points)
Stress on board (16; 5)	0.90	16–77	16–80	43.71	12.09	44.00	17	–0.10 (0.11)	–0.36 (0.21)
Gastrointestinal symptoms (8; 4)	0.90	8–30	8–32	13.35	4.45	13.00	6	0.76 (0.11)	0.18 (0.21)
Cardiovascular symptoms (8; 4)	0.89	8–32	8–32	11.09	3.72	10.00	5	1.43 (0.11)	2.17 (0.21)
Musculoskeletal symptoms (4; 4)	0.82	4–16	4–16	7.54	2.49	8.00	3	0.55 (0.11)	0.15 (0.21)
Mental health (5; 6)	0.82	8–30	5–30	22.50	3.42	23.00	4	–0.52 (0.11)	0.72 (0.21)

Descriptive parameters of the scales of stress and health used in the sample tested (Table 3) show that the level of stress on board is moderate, on average, while physical and mental health is good, on average. More precisely, the distributions of all the physical-symptom scales – gastrointestinal, musculoskeletal and, especially, cardiovascular symptoms – were positively skewed, i.e. average values were below 2 on the 4-point scale. Similarly, mental-health distribution is moderately negatively skewed, with an average value of 4.5 on the 6-point scale. These results are expected, since our participants are derived from a healthy population of seafarers who are subjected to regular medical examination.

3 Results

3.1 Comparison of lifestyle factors at sea and at home

In order to compare prevalence of different lifestyle factors between the on-board and home environments, Chi-Square statistics were used (see Table 1). Significant differences between frequencies in the two situations were found for all the lifestyle factors used: smoking, alcohol use, sleeping, physical exercise, and healthy balanced diet. However, directions of differences varied for used unhealthy factors.

3.1.1 Smoking

The data show that about 42% of the sample are smokers (58% non-smokers). However, higher levels of smoking (the two last categories: 20–30, and more than 30, cigarettes per day) are found at sea (18%) than at home (12.5%).

3.1.2 Alcohol use

About 44.5% of respondents never drink on board, compared to 7% who never drink at home. Weekly and daily use of alcohol (the two last categories) are less frequent on board (nearly 18%) than at home (42%). The data on alcohol quantity show greater prevalence of zero consumption of alcohol in a typical day on board (58%) than in the home situation (about 24%). Since up to two drinks per day is considered as moderate drinking for men [37], frequencies for greater levels of alcohol quantity between the two situations were compared. Consumption of more than 2 drinks in a typical day (last four categories in Table 1) was reported in 10% of cases in the shipping environment, compared to 29% at home.

3.1.3 Sleeping

Since an average adult needs a minimum of 7 hours of sleep per day [38], we compared frequencies for sleeping less than 7 hours/day (first three categories in Table 1) between the shipping and home environments. About 44% of participants reported sleeping less than 7 hours/day while at sea, while percentages for the home situation amount to about 10%.

3.1.4 Physical exercise

Considering 2-3 times per week of physical exercise of a duration of 45–60 minutes as enough exercise (the two last categories in Table 1), the data show higher frequencies of physical exercise on board (46%), than at home (about 37%). The most unfavourable category of physical exercise (never) was high, but relatively similar in the two situations (about 27% on board, compared to nearly 30% at home).

3.1.5 Diet

About 55% of the participants evaluated their diet at sea as unhealthy and unbalanced (categories never and rarely), while percentages for the same categories at home were below 11%.

Overall, the hypothesis of higher prevalence of unhealthy life style in the shipping environment than at home (H1) cannot be confirmed for alcohol consumption and physical exercise. However, differences regarding the data for alcohol between the home and ship environments reflect the alcohol policy of shipping companies. Still, the data showed fewer sleeping hours per day, a more unfavourable diet and higher levels of heavier smoking at sea than at home.

3.2 Relations between stress, lifestyle factors and health

In order to test relations between stress, lifestyle factors and health, Spearman rank-order correlations were used for all bivariate correlations (Table 4). Besides having ordinal-type variables for lifestyle factors, the reason for using non-parametric statistics in testing relations between stress and health scales was the violated assumption of normality in the scales of physical and mental health used (See Table 3 for descriptive statistics).

Table 4
Spearman rank-order correlations between lifestyle factors on board and at home and perceived stress on board and health measures (N = 530)

Stress Gastrointestinal Cardiovascular Musculoskeletal Mental

board symptoms symptoms symptoms health

Smoking on board –0.08 0.06 0.17^* 0.13^ –0.04

Smoking at home –0.11^ 0.04 0.13^ 0.11^** –0.01

Alcohol frequency on board –0.02 –0.02 0.09^* 0.05 0.02

Alcohol frequency at home –0.08 0.01 0.12^ 0.00 –0.04

Alcohol quantity on board –0.02 0.01 0.12^ 0.07 –0.00

Alcohol quantity at home –0.08 0.05 0.13^ 0.04 –0.06

Sleeping on board –0.25^* –0.18^* –0.12^ –0.19^* 0.25^*

Sleeping at home 0.03 0.07 –0.00 0.02 –0.05

Physical exercise on board –0.06 –0.18^* –0.23^* –0.22^* 0.13^

Physical exercise at home 0.07 0.00 –0.10^* –0.07 –0.00

Healthy diet on board –0.28^* –0.34^* –0.20^* –0.26^* 0.27^***

Healthy diet at home –0.06 –0.08 –0.07 –0.09^* 0.23^*

Stress on board 0.33^* 0.27^* 0.30^* –0.38^***

	Stress	Gastrointestinal	Cardiovascular	Musculoskeletal	Mental
Smoking on board	–0.08	0.06	0.17^***	0.13^**	–0.04
Smoking at home	–0.11^**	0.04	0.13^**	0.11^**	–0.01
Alcohol frequency on board	–0.02	–0.02	0.09^*	0.05	0.02
Alcohol frequency at home	–0.08	0.01	0.12^**	0.00	–0.04
Alcohol quantity on board	–0.02	0.01	0.12^**	0.07	–0.00
Alcohol quantity at home	–0.08	0.05	0.13^**	0.04	–0.06
Sleeping on board	–0.25^***	–0.18^***	–0.12^**	–0.19^***	0.25^***
Sleeping at home	0.03	0.07	–0.00	0.02	–0.05
Physical exercise on board	–0.06	–0.18^***	–0.23^***	–0.22^***	0.13^**
Physical exercise at home	0.07	0.00	–0.10^*	–0.07	–0.00
Healthy diet on board	–0.28^***	–0.34^***	–0.20^***	–0.26^***	0.27^***
Healthy diet at home	–0.06	–0.08	–0.07	–0.09^*	0.23^***
Stress on board		0.33^***	0.27^***	0.30^***	–0.38^***

Note: ^*p < 0.05, ^**p < 0.01, ^***p < 0.001.

Since outcome measures (stress and health) were checked against a large number of hypothesized predictors – we tested 64 hypotheses or correlations – a Bonferroni-adjusted significance level of 0.00083 was calculated to account for the increased possibility of type-I error. Therefore, only correlations noted as ^***p < 0.001 should be considered as significant (see Table 4). For example, the significant correlates of cardiovascular symptoms after correction are only the following: smoking at sea, scarceness of physical exercise at sea, unhealthy diet at sea, and stress on board.

Using the correction mentioned, the most consistent negative correlates of physical and mental health measures are the following lifestyle factors at sea: unhealthy diet, lack of physical exercise, low number of sleeping hours, and smoking. More precisely, healthy diet on board was related to lower levels of all physical symptoms and higher level of mental health, physical exercise on board was related to lower levels of all physical symptoms, sleeping hours at sea was related to lower levels of gastrointestinal and musculoskeletal symptoms and a higher level of mental health, and smoking on board was related to a higher level of cardiovascular symptoms (see Table 4). In addition, a healthy diet at home was related to better mental health. Overall, the hypothesis about relations between different lifestyle factors and health (H2) was partially confirmed.

Stress on board is significantly correlated with higher levels of gastrointestinal, cardiovascular and musculoskeletal symptoms, and a lower level of mental health. The correlations obtained are moderate. Therefore hypothesis H3, about relations between stress on board and different aspects of physical and mental health, is completely confirmed.

The data on relations between stress and unhealthy life-style factors are largely not in accordance with the assumption about unhealthy life style as a result of a negative way of coping with stress (H4). More precisely, alcohol use, physical exercise and smoking at home did not correlate with stress. The only significant correlates of stress on board were a lower number of sleeping hours and unhealthy diet at sea. However, neither diet nor number of sleeping hours at sea lies within the direct control of seafarers.

4 Discussion

Unhealthy lifestyle factors play a very important role in research on links between stress and health in seafarers. However, to our knowledge this was the first study which compared the prevalence of different lifestyle factors between the home and ship environments.

In accordance with initial assumptions, the data showed that seafarers sleep less at sea, their diet on board is more unhealthy and unbalanced, than at home, and smokers smoke more cigarettes per day while on board. The data on sleeping hours at sea is in line with earlier findings about fatigue in seafarers [14 , 17], and may be regarded, at least partially, as a consequence of long working hours [13], which are often under-recorded [15]. In spite of the great importance of diet for health, diet on board has been posed as an important research question only in recent times. Oldenburg et al. [39] noted that seafarers have limited influence on the quality and quantity of food during their stay on board, while Hjarnoe and Leppin [40] noted numerous barriers to the promotion of a healthy diet at sea. Although our data relies only on self-report, the fact that more than half the sample evaluated their diet on board as unhealthy and unbalanced is worrying. The data also indicated higher smoking levels on board than at home, but only for heavier smokers (more than 20 cigarettes per day). Furthermore, data (Table 1) showed about 42% smokers in total in tested sample, which is higher than the already high national prevalence. A European health study [41] showed that Croatia has one of the largest prevalences of daily smokers among EU countries (35%).

The data relating to comparisons of physical exercise and alcohol use between the two environments follow different directions. The results indicated that favourable levels of physical exercise are more prevalent at sea, which may be explained as the use of a compensation strategy while on board for some seafarers. This also indicates that at least part of the sample has good opportunities for physical exercise on board. This is important, because limited opportunities for recreation are regarded as an important source of stress which impairs seafarers’ physical, psychological and social well-being [6, 10]. However, the data showed that about half of the sample never exercise, or perform physical exercises rarely, both at home and at sea, and this leaves room for promoting sporting activities in seafarers.

The large difference between the on-board and home environments regarding use of alcohol stems from policies and prevention programmes to control alcohol abuse in the shipping workplace. However, as this data relies on self-reports, there is a possibility that alcohol consumption at sea is higher than reported. While consumption and possession of drugs is strictly prohibited on all ships, permission for alcohol consumption differs among shipping companies. Alcohol policies on shipping companies are based on guidelines provided by the ICS (International Chamber of Shipping), OCIMF (Oil Companies International Marine Forum), and IMO (International Maritime Organization). Some companies allow ‘controlled’ alcohol consumption during the period outside working hours plus the 4 hours prior to working hours, but there are also differences among companies regarding maximum blood alcohol content during working and non-working time, with a ‘zero’ policy on some. In order to control this, seafarers are subjected to testing and screening for drugs and alcohol abuse by routine medical examination and un-announced testing. Regarding the data on alcohol consumption at home, it has to be noted that alcohol consumption in Croatia is similar to the EU average [42], but also that the EU region has the highest alcohol consumption in the world [42].

Relations obtained between lifestyle factors and health are in accordance with previous findings about the importance of unhealthy factors for seafarers’ health [28]; here, sleep deprivation, lack of physical exercise, unhealthy diet and smoking are shown in our research as the most consistent negative correlates of health. The study also confirmed the hypothesis on the association of perceived stress on board with higher levels of gastrointestinal, cardiovascular and musculoskeletal symptoms, and a lower level of mental health. However, the cross-sectional design of the study does not enable any causal conclusions. The correlations obtained between stress on board and health may be explained in different directions than that predicted by stress models. Therefore, it is possible that individuals with lower levels of physical and/or mental health perceive greater stress. Also, because of the healthy-worker effect, these associations might also be underestimated in the sample.

On the other hand, the hypothesis about unhealthy factors as a result of a way of coping cannot be confirmed. For example, results of the study did not show that those who perceived greater stress smoke more or drink more, or take less physical exercise. On the other hand, data showed that stress is related to less sleeping and an unhealthy diet, but these two factors are not under the direct control of the seafarers. Therefore, the logical explanation of these results is that deprivation of sleep as a consequence of workload, as well as the issue of unfavourable diet on board, contributes to the overall perception of stress on board.

Besides the cross-sectional design, which does not allow any causal conclusions about the relations between stress, lifestyle factors and health, a few additional possible limitations need to be discussed. The drawbacks of on-line surveys include a threat to the validity of the data stemming from the fact that the researchers cannot monitor the identity and truthfulness of participants. However, the possibility that data was flawed in this way is small. Studies which compare traditional (paper-and-pencil) and on-line surveys have shown that the results obtained by internet surveys do not appear to be tainted by false data or repeat responders and are, so far, consistent with results from traditional methods [43, 44]. Therefore, the limitations of the study include the general disadvantages of self-report measures, such as social-desirability bias and unwillingness to reveal private details about one’s feelings or attitudes regarding the job. However, with anonymous participation in the on-line survey and instructions relating to the study procedure obtained from a neutral researcher, these effects are minimized in the study. On the other hand, it still might be possible that participants have exaggerated their self-reports in some direction.

The non-probabilistic sampling procedure is a further limitation of obtained results. Because of the questionable representativeness of the sample used, data cannot be generalised to the target population (Croatian seafarers). Since the study relied on voluntary participation, the data may be biased. In Croatia there are approximately 20,000 seafarers, of which 15,184 take part in international sea shipping [45]. Comparisons of ranks and professions within the sample with official statistics (official statistics of seafarers in international shipping, by the Ministry of Maritime Affairs, Transport and Infrastructure) show that higher ranks are overrepresented in the sample. However, we considered that the use of the sampling procedure described, which increases confidence in anonymity for participants, since the seafarers experience us as neutral researchers in no way related to their company or agency, leads to a relatively large sample of this hard-to-reach population. Overall, in spite of the limitations, we considered the sample sufficient to investigate the tested comparisons of lifestyle factors in the two situations and the relations between lifestyle factors, stress and self-rated health.

On the basis of the data obtained and general knowledge of smoking and alcohol abuse as main risk factors for disease and mortality in Europe [46, 47], anti-smoking and anti-alcohol campaigns among seafarers are strongly recommended. Based on the results, which showed that seafarers with a greater level of physical exercise are less prone to physical and mental symptoms, promoting sporting activities on board, and also among seafarers at home, is very important. Recent quasi-experimental study outside this work population showed that engaging in workplace exercise has positive effect on health behaviour and willingness to become more physically active [48]. The results obtained also imply that shipping companies need to put more effort into promoting health and a balanced diet on board, as well as sleep hygiene, and in that way promote the health of their employees. In our opinion, sleep deprivation on board is a direct consequence of high workload, and should be minimised by primary strategies, such as reduction of long working hours, increased number of crew and unbroken periods of rest and sleep. Besides the importance of lifestyle for individual health, managers of shipping organizations should also be aware that issue of seafarers’ lifestyle is important for productivity also, since results from broader area showed that healthy lifestyle of employees is important correlate of their vitality at work [49].

5 Conclusion

Data indicated higher sleep deprivation, more unhealthy diet, and higher levels of heavy smoking in the shipping environment than at home. On the other hand, prevalence of alcohol use and physical exercise is more unfavourable at home than in the shipping environment. Further, sleep deprivation, unhealthy diet, lack of physical exercise, and smoking are shown as negative correlates of various measures of physical and mental health. Finally, stress on board was associated with sleep deprivation and unhealthy diet, and with lower levels of physical and mental health.

Conflict of interest

The authors have no conflict of interest to report.

Footnotes

Acknowledgments

The authors thank all seafarers who participated in this study. Furthermore, we are grateful to all organisations and individuals who helped us with advertisement and/or conducting of our study.

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