Further stages in his career were at the Technical University of Munich, the University of Regensburg and the Department of Health Policy and Management & Department of Family Medicine at the University of California in Los Angeles. His current focus of research is on the impact of physical activity on psychiatric, cardiometabolic and cancerous diseases, as well as the effects on pulmonary diseases and cancer of taking cannabis. At the Centre for Dental, Oral and Maxillo-Facial Surgery he is investigating causal determinants of periodontitis and is developing data-assisted decision support systems in the treatment of periodontitis.