Recruitment and Randomization
RECRUITMENT
A random selection of GPs was gradually contacted during the study period by the study centers by post or email followed by telephone calls or practice visits to provide information and conduct recruitment. Once recruited, the GPs were asked to consecutively approach potentially suitable study participants from their list of older patients and enroll them in the study until an average number of 5 participants per practice (cluster) was reached. The GPs were not aware of their group assignment at the time of patient recruitment. Cluster randomization was conducted at the practice level, in which all participating GPs from a practice were assigned together to either the intervention or control group. The allocation sequence was computer generated and concealed from researchers. Block randomization (block size 4) and stratification by centers were used to ensure equal distribution across the study sites. An experienced biometrician at Hannover Medical School (B.W.) performed randomization after recruitment of the participants.