Unravelling disease activity in IBD ; a key to personalized medicin: Epidemiological patterns, modifiable risk factors, and treatment implications

Inflammatory bowel disease (IBD) is a chronic condition of the gastrointestinal tract and is characterized by recurring periods of disease activity and remission. The aim of this thesis was to further analyse the disease course (part 1), to search for modifiable risk factors (part 2) and to investigate the consequences of both chronic disease activity and its inherent treatment. In the first part, it was shown that a large amount of patients experiences a quiescent disease course. However, it appears hard to predict the disease course in individual patients. These findings underline the need for personalized treatment strategies. In the second part, no association was observed between ambient air quality and disease activity, but an association with psychosocial factors, such as stress and life events, and malnutrition was present in the studies. Negative changes in these factors appear to precede disease activity and are therefore potential targets for personalized interventions. In the third part, it was observed that the cancer risk in a part of IBD patients was increased. This was mainly due to the use of aggressive drugs. Considering colorectal cancer, which is a possible consequence of chronic disease activity, only a slightly increased risk in a small subset of patients was observed.