Effect of eight-form Tai Chi combined with olfactory stimulation on working memory in older adults with mild cognitive impairment

Background Tai Chi integrates multisensory stimuli, including olfactory cues, to enhance cognitive functions such as working memory. This study evaluated the effects of eight-form Tai Chi combined with olfactory stimulation on working memory in older adults with mild cognitive impairment (MCI). Methods This study used a 2 (time) × 3 (group) mixed design. Of 267 screened patients with MCI, 93 were deemed eligible and randomly assigned to one of three groups: Tai Chi group (TCG), Tai Chi combined with olfactory stimulation group (TCOG), or control group (CG). The TCG and TCOG participated in three weekly 60 min sessions for 26 weeks. The TCOG was exposed to four fragrances. Primary outcomes were the N-back task and the digit span test (DST). Secondary outcomes included the MoCA, MMSE, CSIT, GDS, SAS, and PSQI. Results Post-intervention, both intervention groups outperformed the CG in 0-back accuracy (TCG: +0.118, 95% CI: 0.048–0.188, p < 0.001; TCOG: +0.118, 95% CI: 0.048–0.187, p < 0.001) and total DST scores (TCG: +1.321, 95% CI: 0.250–2.393, p = 0.009; TCOG: +1.535, 95% CI: 0.602–2.467, p < 0.001). They also exhibited significant improvements in MoCA (TCG: +3.07, 95% CI: 0.89–5.25, p = 0.002; TCOG: +3.42, 95% CI: 1.22–5.62, p = 0.001) and CSIT scores (TCG: +3.29, 95% CI: 1.56–5.01, p < 0.001; TCOG: +3.86, 95% CI: 2.28–5.44, p < 0.001) compared with the CG. Furthermore, the TCOG showed superior gains over the TCG in 1-back accuracy (+0.156, 95% CI: 0.044–0.269, p = 0.003), forward digit span (+0.613, 95% CI: 0.156–1.070, p = 0.004), and backward digit span (+0.921, 95% CI: 0.117–1.726, p = 0.018). It likewise showed significantly greater reductions in GDS (−1.46, 95% CI: −2.78 to −0.15, p = 0.024) and PSQI scores (−2.04, 95% CI: −3.89 to −0.19, p = 0.008) compared with the other groups, with the TCOG versus TCG in PSQI being significant (−1.47, 95% CI: −2.98 to −0.04, p = 0.020). Conclusion Tai Chi improved working memory and global cognition in older adults with MCI. Combining Tai Chi with olfactory stimulation yielded additional benefits, demonstrating superior efficacy in alleviating depressive symptoms and enhancing sleep quality. Clinical trial registration https://www.chictr.org.cn/index.html , Chinese Clinical Trial Registry (ChiCTR2400083424).