Like many medical studies, the Berlin Aging Study II (BASE-II) is based on a non-random "gconvenience sample" of self-recruited participants. To study processes of selectivity in BASE-II, we used a questionnaire to compare BASE-II with a large, representative reference study, the German...

The Berlin Aging Study II (BASE-II) is a multidisciplinary study that allows for the investigation of how a multitude of health status factors as well as many other social and economic outcomes interplay. The sample consists of 1,600 participants aged 60 to 80, and 600 participants aged 20 to...