Association Between Hydrogen-Rich Water Consumption and Lower Extremity Function in Older Adults Participating in Community Salons: A Prospective Observational Study

Abstract Background Falls among older adults are a leading cause of fractures, loss of independence, and need for long-term care. Community salons in Japan promote social participation and health activities among older adults. Hydrogen-rich water is widely used as a health product, but evidence in community settings remains limited. Methods We conducted a prospective observational study among 48 community-dwelling older adults attending community salons in Hiroshima City, Japan. Hydrogen-rich water was offered by the salon operators as part of routine activities; the research team did not assign participants to consume it. Participants were categorized at baseline according to their usual hydrogen-rich water consumption at the salons (consumers vs non-consumers) and followed for six months. The primary outcome was the 30-second chair stand test (CS-30). Secondary outcomes included the Timed Up and Go test (TUG), usual gait speed, one-leg stance time, and grip strength. Within-group changes and between-group differences in change scores were compared. Results All 48 participants completed follow-up, and no serious adverse events were reported during the study period. The consumers group showed a greater improvement in CS-30 over six months (baseline 12.96 (SD 3.21) to follow-up 14.52 (SD 3.59); change 1.57 (SD 2.41)) compared with the non-consumers group (12.52 (SD 3.00) to 12.22 (SD 3.54); change −0.30 (SD 1.55)), with a significant between-group difference in change scores (p=0.003). The consumers group also showed a greater increase in usual gait speed (0.91 (SD 0.24) to 0.98 (SD 0.26); change 0.07 (SD 0.08)) than the non-consumers group (0.94 (SD 0.24) to 0.97 (SD 0.22); change 0.03 (SD 0.05); p=0.008). No significant between-group differences were observed for TUG (p=0.57), one-leg stance time (p=0.13), or grip strength (p=0.10). Conclusion In community-dwelling older adults participating in community salons, routine hydrogen-rich water consumption was associated with improved lower extremity function as measured by CS-30 and gait speed. Because exposure was not randomized, residual confounding cannot be excluded, and causal inference is limited. Larger studies with stronger designs are warranted.