We conducted a prospective, multicenter (cities of Leipzig and Halle), randomized, controlled trial with follow-up examination after 18 months. Participants were randomized to an intervention group or to a control group using balanced blockwise randomization stratified by center. Participants and field researchers could not be blinded to group allocation. However, a statistician not involved in the trial (ie, “blinded”) conducted the final statistical analysis and only pseudony- mized data were analyzed. We stored personal data on all participants (including name and address) separately from the trial data (both in lockable cabinets in lockable rooms). All personal data were treated confidentially. The ethics com- mittees of the universities of Halle and Leipzig approved the study protocol. Research was carried out in compliance with the Declaration of Helsinki. All subjects gave their written informed consent for participation in the study. The study is registered in the ClinicalTrials.gov registry (NCT00644826). The study design and methods have been described in detail elsewhere