2026 Volume 40 Issue 3 Pages 167-177
Lip closure strength is essential for maintaining oral function and tends to decline with age, potentially leading to dysphagia and a reduced quality of life in older adults. This study examined the effectiveness of a simple“bubble rinsing”exercise in improving lip closure strength using a crossover trial design. Participants included 36 community-dwelling older adults（mean age：77.3 years）and 35 residents of long-term care facilities（mean age：89.6 years）, all aged 65 years or older and living in Tokyo. The intervention consisted of performing a simulated vigorous oral rinsing motion without water（“bubble rinsing”）for one minute, twice daily, over an 8-week period. Each participant group was randomly assigned to begin with either the intervention or control phase（no exercise）, followed by a 4-week washout period, then crossed over to the alternate phase. Lip closure strength was measured at baseline and at 4-week intervals. A mixed-effects model was used to examine the effects of sequence, period, and treatment. In the community-dwelling group, the intervention produced a significantly greater improvement in lip closure strength compared to the control phase（mean difference：5.3 N, p＜0.001）. Similarly, in the institutionalized group, lip closure strength increased by 3.1 N after the intervention, also showing a significant improvement over the control condition（p＜0.001）. A significant main effect of the intervention was observed in both groups. These findings suggest that bubble rinsing is an effective and low-burden exercise for improving lip closure strength in older adults and may help preserve oral function and prevent oral frailty in aging populations.
