Illness, disease, and sickness absence: an empirical test of differences between concepts of ill health

Objectives: In studies of public health and morbidity different concepts of ill health are often seen as interchangeable alternatives. With the help of extensive population information this research intends to show how different concepts and measurements produce very different pictures of health and ill health. The concept trilogy of illness,'' disease,'' and sickness'' is used to capture different aspects of ill health. Design: Cross sectional data were obtained through comprehensive interview surveys 1988 - 2001 and registers of sickness absence. Because of lack of data some years had to be excluded. Settings: Swedish population. Participants: Annual data for around 3500 employed and self employed persons. Main results: Most people have some sort of illness or complaint. Fewer could be registered with a disease. Even fewer had been on sick leave. The overlap was fairly low. There also was an obvious discrepancy between reporting having a disease and a subject's rating of general health. It was shown that the different concepts showed different trends over time. Conclusions: The discrepancies between the concepts imply that you have to be very careful when using public health data to illustrate different aspects of morbidity. The comparatively low degree of overlap between them shows that they represent different realities. There is a need to do further empirical research about how different aspects of morbidity are interrelated. Their lack of interrelation seems to be an important research area worth developing further.