Abstract
BACKGROUND: Japan's population is aging rapidly, and the proportion of older adults living alone is increasing. Some older adults relocate owing to aging housing, health issues, or financial difficulties. In certain cases, they move closer to adult children to improve access to support-referred to in Japan as yobiyose. Such relocations can pose psychosocial risks, including social isolation, depression, and reduced quality of life (QoL), particularly when individuals face challenges in adjusting to unfamiliar communities. Although Japan promotes "Aging in Place," many services rely on self-initiated access, which can exclude socially vulnerable older adults. Research on practical support in the early post-relocation phase (i.e., critical time) remains scarce. METHODS: This quasi-experimental study examines the feasibility and effectiveness of the Welcome Project, a community-based intervention targeting older adults living alone who have recently relocated to a large public housing complex in Tokyo. Participants self-select into the intervention or control group. The intervention includes professional accompaniment for greeting neighbours and participation in monthly community gatherings, provided by trained public health nurses and other professionals. Primary and secondary outcomes-subjective QoL (measured by CASP-19), frequency of interpersonal interactions, and attitudes toward the community-are assessed over a three-month period. The program is delivered through CoCo-Kara Station, a multidisciplinary community support hub. DISCUSSION: This study addresses a gap in the evidence by evaluating a critical-time-intervention model to support community adjustment among recently relocated older adults. The program's collaboration with local municipalities, the Urban Renaissance Agency (UR), and community support centres enhances its feasibility and broader practical potential. While the non-randomized design and short follow-up period are limitations, the findings can inform sustainable models of support for older adults at risk of social isolation. TRIAL REGISTRATION: This study was retrospectively registered in the UMIN Clinical Trials Registry (UMIN-CTR) on July 7, 2025 (UMIN000058386).