Cardiovascular diseases among Danish seafarers

Background
Seafarers’ work environment and conditions are substantially different compared to most land-based occupations. This includes long workdays, monotonous work, night shifts, separation from family and friends for longer periods and psychosocial problems, such as insufficient separation between work and spare time. All these different work conditions might increase the risk of cardiovascular diseases. Cardiovascular diseases are a major health problem worldwide, and especially within seafaring, as an acute cardiovascular event aboard might have fatal consequences, since the crucial medical care can be far away. This means that a seafarer having a life-threatening cardiovascular event may have to wait for hours or even days to get the proper medical treatment. Since cardiovascular diseases can have fatal consequences for seafarers, it is extremely important to investigate the risk of cardiovascular diseases in order to create targeted health interventions.

Purpose and research questions
The main purpose of the PhD project is to investigate if there is an association between being a seafarer and the risk of cardiovascular diseases. This is done by examining:
1) Changes in incidence and mortality among Danish seafarers over a 30-year period compared to the employed population in Denmark.
2) The association between the seafarer’s position aboard and the risk of cardiovascular diseases among Danish seafarers.
3) The association between type of vessel and the risk of cardiovascular diseases among Danish seafarers.
4) If the Danish seafarers have a better or worse prognosis of survival compared to other occupations.

Methods
It is a register-based study including all seafarers with a Danish civil registration number, and it covers the period from 1986 to 2016. Data used for analyses will be drawn from the data register BLUE (established at CMSS, SDU) and The Danish Maritime Authority. BLUE provides data from the National Patient Register, which holds information about hospitalisations, and the Cause of Death Register, while data from The Danish Maritime Authority includes information about the seafarers, such as dates for signing on and off, type of vessel and job position aboard. The main statistical analyses to answer the research questions will be survival analyses, while other analyses also will be included. The survival analyses will consist of Cox regression and Kaplan-Meier graphs and analyses, whereas other statistical analyses will be e.g. Poisson and logistic regression. The outcome is hospitalisations and mortality due to cardiovascular diseases. To get a more accurate picture of the risk of cardiovascular diseases, all analyses will be adjusted for relevant factors, such as gender, age, income, social status, etc. Possible factors affecting the association will be identified through literature studies, and DAGs (directed acyclic graphs) will be used to identify the factors that should be included in the analyses.

Time schedule
June 2021 - June 2024

PhD student
The project is carried out by PhD student Anna Uhd Bøge. 

Supervisors
Senior researcher Kimmo Herttua, Centre of Maritime Health and Society, SDU (main supervisor)
Professor Rune Lindahl-Jacobsen, Unit for Epidemiology, Biostatistics and Biodemography, SDU (co-supervisor)
Associate professor Linda Juel Ahrenfeldt, Unit for Epidemiology, Biostatistics and Biodemography, SDU (co-supervisor)