ABSTRACT
This quote comes from the website of the WHO, the World Health Organization. It gives a definition of chronic disease and an impression of the importance of chronic diseases in health care.
This chapter is dedicated to dynamic prediction models in chronic disease. Such models are important for treatment choice and patient counseling and can also be helpful in understanding the time course of the disease. In a simplified model of chronic disease different stages of the disease can be defined S0,S1, ..,Sk where S0 = “No disease,” Sk−1 = “End-stage disease” and Sk = “Death.” This could be seen as a special case of a multi-state model, where the states can be ordered according to the severity of the disease coming with worsening prognosis. In the simplest (and most pessimistic) situation a patient progresses through the consecutive stages to die eventually. Actually, this might not be true for two reasons. The first, positive, reason is that the patient might respond to treatment which will bring her/him back to a less severe stage or even to S0 = “No disease.” The second, negative, reason is that the patient progresses so quickly that intermediate stages are not observed.
