User:Dane (usurped)/The Introduction

Epidemiology is often regarded as a central part of all types of health practices, whether this is the practice of health examinations, disease treatment, prevention activity, administration, policymaking or research activity. However, in maritime health, the epidemiologic method has not been used very widely and the aim of this module is to encourage to use the epidemiology in maritime health much more.

To understand the basic concepts, prevalence and incidence, their different forms, the relative measures of these in different strata in the populations and the relation to the time perspective in the populations, is the primary goal. Populations are aging, dying, migrating, newborns are coming in and the exposures in the surroundings are continuously changing year by year, not at least in the maritime area. The disease patterns change from mild to severe forms and sometimes with total recovery. This should be considered in the epidemiological studies.

Take a helicopter perspective and imagine how the exposures and the life and health events changes over time and varies in the different social and geographical strata and poses different health problems. In addition, use a close-up perspective to perform the details of the studies. The health events happen and changes in the populations over time with different health problems are the objects of studies.

The events occurring in a study population over time can be seen as a particular part of the humans´ and the natures´ own unconscious experimental population that was chosen as the object of study. Alternatively, the study populations are the consciously chosen populations used for experiments initiated by the humans, intervention studies, prognostic studies or clinical trials in which we consciously introduce supposed health bringing changes.

Epidemiology in practice
Multifactorial disease models with a multitude of causal risk factors and health promoting factors are probably often used for planning of the studies. Probably, because this is not always expressed in the published papers with the results. Nevertheless, is it believable that anybody would initiate a large study without using a disease model, even unconsciously? There is nothing as practical as a good theory! (See Power Point presentation 1, with some theoretical models). Having described the health problems, the presumed theoretical interactions in the causal web of the different determinants in the study population and the aims of the study, we chose the specific type of study population, which is best suited for the aims of the study.

Theory
Theoretical models are useful to point out which types of risk factors or health bringing factors that is relevant to be studied in relation to the health problem and the aim of a study. There is a logical correspondence between the main types of epidemiological studies and the main types of health activities in general practice. The type of study relates to the aims in general of the studies while the study design or research design relates to the procedures and methods to be adhered to in conducting a research project. Within each type of study are used different study designs (Figure 1 and 2).