Kaare Christensen, Danish epidemiologist and biostatistician at the University of Southern Denmark, visited the group of Molecular Epidemiology to discuss collaboration within the ZonMW Open Competition project investigating the socio-genetic pathways of human ageing rate and longevity. The research group of this project headed by Eline Slagboom including Niels van Berg, Pasquale Putter, Mar Rodriguez-Girondo and Marian Beekman discussed potential research questions that can be answered especially by the group of Kaare Christensen in Odense by the use of the valuable Danish register data. His visit to Leiden accelerated the collaboration between the two research groups.