Effects of a Community-Based Multi-Component Intervention on Subjective Well-Being in Older Adults: The Chofu–Digital–Choju Project in Japan

<b>Background:</b> Subjective well-being (SWB) is an essential indicator of successful aging. Although social connections enhance SWB among older adults, few interventions have integrated community-based approaches with information and communication technology (ICT). This study evaluated the Chofu-Digital-Choju (CDC) project, a multi-component community intervention fostering in-person and online social connections among community-dwelling older adults in urban Japan. <b>Methods:</b> This quasi-experimental study (January 2022 to March 2024) included community-dwelling older adults aged 65-84 years in Chofu City, Tokyo, Japan. The intervention consisted of online classes, community hubs as local third places, and community events. Baseline and follow-up data were collected using self-administered questionnaires. Propensity score matching (1:1) was used to reduce selection bias, and generalized estimating equations were applied to evaluate the intervention effects. The primary outcome was SWB (Cantril Ladder). The secondary outcomes included social isolation, neighborhood relationships, social participation, health literacy, psychological health, physical activity, and ICT use. <b>Results:</b> Among the 1599 participants who completed both surveys, 209 (13.1%) participated in at least one CDC intervention component. After propensity score matching, 195 pairs were analyzed. No significant interaction effect was observed for SWB (β = 0.08, 95% confidence interval [CI]: -0.20, 0.37; <i>p</i> = 0.565). However, a significant interaction effect favored the intervention group for Internet usage frequency (odds ratio = 1.53, 95% CI: 1.08, 2.16; <i>p</i> = 0.016). A significant borderline interaction was also observed in health literacy (β = 0.13, 95% CI: -0.00, 0.26; <i>p</i> = 0.056), which reached significance in covariate-adjusted sensitivity analysis (<i>p</i> = 0.044). Subgroup analyses revealed that community hub participants showed significant interaction effects in health literacy (<i>p</i> = 0.021) and a trend toward reduced depressive symptoms (<i>p</i> = 0.084). <b>Conclusions:</b> The CDC intervention did not improve SWB over 2 years but enhanced Internet use and supported health literacy and depressive symptoms, particularly among hub participants. Community-based, multi-component interventions that integrate online and in-person activities may foster digital inclusion and specific health behaviors. Although SWB did not change in this study, these proximal gains may serve as foundational steps for long-term improvement. The study protocol was preregistered in the UMIN Clinical Trials Registry (UMIN000051393; Registered on 21 June 2023).