Short-term, nudge-based strategies to promote physical activity in community-dwelling older adults: a pilot randomized crossover trial

Objective: Physical activity is essential for healthy aging. This pilot study preliminarily examined whether a short-term nudge-based behavioral intervention could influence objectively measured physical activity patterns and ensure psychological safety in community-dwelling older adults. Methods: A randomized, 2-period crossover trial was conducted with 23 community-dwelling older adults (final n = 22). Participants were assigned to intervention-control or control-intervention sequences (2 weeks each, with a 1-week washout). The intervention included mailed leaflets and follow-up telephone messages based on the MINDSPACE framework. Physical activity (LPA, SB, MVPA) was assessed using triaxial accelerometers, and depressive symptoms (GDS-15) were monitored as an exploratory safety outcome. Results: No significant carryover effects were observed. Crossover analysis indicated a significant increase in light-intensity physical activity (LPA) during the intervention period compared with the control period (35.1 min/day, p = 0.036, Cohen’s d = 0.96). However, no significant Time × Group interaction was observed in the supplementary RM-ANOVA. No significant changes were observed in sedentary behavior, moderate-to-vigorous physical activity, or depressive symptoms, which remained stable and low throughout the study. Conclusion: This pilot study provides preliminary evidence that a short-term, nudge-based intervention may induce a potential shift toward increased LPA, potentially reflecting behavioral reorganization. The intervention did not adversely affect mood, supporting its psychological safety. Future fully powered trials are required to confirm these exploratory findings.