2.4. Study Design
The study was a cluster-randomized, single-blind, and parallel controlled trial that consisted of a 3-month treatment period and another 3-month follow-up. According to the cluster size and location of the community centers, each community center was randomly allocated to either the control or the intervention group. Participants in the same community centers were allocated to the same treatment, so that they were masked to the treatment allocation. The random assignment of community centers to treatment groups was performed with Minim software (version 1.5; London Hospital Medical College) [