Tai Chi exercise improves sleep quality in older adults with mild insomnia by enhancing slow-wave activity during deep sleep: a 12-week randomized controlled trial

Background Sleep quality declines with age in older adults, and pharmacological interventions have multiple limitations. As a safe and accessible mind-body exercise, Tai Chi has preliminary evidence supporting its sleep-improving effects, but objective mechanistic studies based on sleep electroencephalography (EEG) remain scarce. Objective: This study aimed to clarify the effect of Tai Chi intervention on improving sleep quality in older adults and reveal its core mechanism through regulating sleep EEG characteristics, using a combination of questionnaires and sleep EEG monitoring. Methods A randomized controlled trial design was adopted, enrolling 67 older adults aged 65–75 years with mild sleep disturbance, who were randomly divided into the Tai Chi group (n=33) and the control group (n=34). The Tai Chi group received 12 weeks of standardized 24-form Tai Chi training (5 times per week, 60 minutes per session), while the control group maintained daily activities without regular exercise. Subjective sleep quality was assessed using the Pittsburgh Sleep Quality Index (PSQI) and sleep diaries. Meanwhile, polysomnography (PSG) was used to collect sleep EEG data, analyzing sleep structure (proportion of each sleep stage) and EEG activity characteristics (slow-wave power, sleep spindle density). Results After intervention, the total PSQI score and sleep onset latency in the Tai Chi group were significantly reduced, and sleep efficiency was significantly enhanced ( P 0.001). PSG results showed that the proportion of deep sleep stage (N3) in the Tai Chi group increased by 23.1%, delta wave power (0.5-4Hz) was significantly enhanced ( P 0.01), and sleep spindle density (N2 stage) increased by 6.0% ( P = 0.07, marginally significant), while no significant changes were observed in sleep indicators of the control group. Correlation analysis revealed that the reduction in total PSQI score was significantly negatively correlated with the increase in N3 stage proportion (r=-0.464, P = 0.0065) and the enhancement of delta wave power (r=-0.382, P = 0.028) in the Tai Chi group. Conclusion Twelve-week Tai Chi exercise intervention can significantly improve subjective and objective sleep quality in older adults. Its core mechanism is related to enhancing slow-wave activity during deep sleep and optimizing N2 stage sleep spindle density, providing objective EEG evidence for the non-pharmacological intervention of Tai Chi in sleep disorders of older adults.