Table 1 Characteristics of the study population and the working environment

Age

Gender (female)

 ≥ 7th grade - technical school

 Gymnasium education

 Vocational training

 University college and university

 Officers

 Non-officers

Living with a partner (yes)

Children under six years old (yes)

 Company 1

 Company 2

 Terminal

 Ferry ship

Number of workdays per week

 Day and evening

 Day, evening and night

Sleeping at the workplace/on board (yes)

 0–4 h per week. Low intensity

 ≥ 2 h per week. High intensity

Smoking (yes)

Sleeping troubles (0 (low)-25–50–75-100 (high))

Job demands (0 (low)-25–50–75-100 (high))

Work-family conflict (0 (low)-25–50–75-100 (high))

Support from supervisor (0 (low)-25–50–75-100 (high))

SOFI Lack of energy (0 (very low)–6 (very high))

SOFI Physical exertion (0 (very low)–6 (very high))

SOFI Physical discomfort (0 (very low)–6 (very high))

SOFI Lack of motivation (0 (very low) – 6 (very high))

SOFI Sleepiness (0 (very low)– 6 (very high))