Additional Effects of 1-Hz rTMS Combined With Tai Chi Chuan on Dual-Task Performance Among Older Adults With Sleep Disorders and MCI: An fNIRS-Based Randomized Controlled Trial.

The short version

This sham-controlled randomized trial with 103 analyzed older adults tested whether adding a form of non-invasive brain stimulation, 1-Hz repetitive transcranial magnetic stimulation (rTMS), to Tai Chi Chuan improves the ability to walk and think at the same time. Participants aged 60-75 had a diagnosed sleep disorder and mild cognitive impairment (MCI, noticeable memory decline without dementia). Doing two tasks at once, known as dual-tasking, depends on sharing limited attention between movement and thinking, and the authors note that poor sleep and MCI can both weaken this attention control. Everyone practiced Yang-style 24-form Tai Chi Chuan for 60 minutes, five mornings a week for 6 weeks. In the evenings, half also received real rTMS, magnetic pulses at 1 Hz delivered for 20 minutes over the right dorsolateral prefrontal cortex (a front-of-brain area involved in attention and planning), guided by each person's MRI scan; the other half received sham stimulation with a look-alike coil. To measure performance, participants walked on a treadmill while subtracting 7 from numbers between 200 and 300, and a head-worn fNIRS cap recorded blood-oxygen changes in the frontal brain. After 6 weeks, the real-rTMS group improved more in subtraction accuracy while walking (P = 0.005; baseline accuracy was about 79.6% versus 77.8%) and scored higher afterward (P < 0.001). They also made more correct subtraction responses afterward (P = 0.001), although the change in total responses did not differ between groups. Their balance (Brief-BESTest) improved more (P = 0.021), and sleep quality scores (PSQI) fell more (P < 0.001). Brain imaging showed larger increases in activity in the left prefrontal cortex and frontal pole during dual-tasking (both P = 0.003) and stronger links between premotor and frontal regions (P = 0.001 or lower). Bigger activity and connectivity changes went along with bigger accuracy and balance gains (correlations r = 0.30 to 0.48). Adverse events were not reported. The authors conclude that rTMS added to Tai Chi improved dual-task performance and may act through frontal and premotor networks. They list limitations: no Tai Chi-only or rTMS-only comparison group, possible leftover expectation effects, unexamined stimulation settings, and imaging limited to the front of the brain. Safety was not described, the participants came from one community in China, and the paper reports mostly P values rather than effect sizes or confidence intervals, so the size of the benefit is hard to judge.

Key findings

• In a 6-week sham-controlled trial of 103 adults aged 60-75 with sleep disorders and mild cognitive impairment (MCI, memory decline without dementia), adding 1-Hz magnetic brain stimulation (rTMS) to Tai Chi Chuan improved accuracy of subtracting 7 while walking on a treadmill more than sham stimulation did (P = 0.005).
• The stimulation group also improved more on a balance test (Brief-BESTest, P = 0.021) and a sleep-quality questionnaire (PSQI, P < 0.001).
• Brain imaging with fNIRS (a light-based measure of blood oxygen) showed larger activation in the left dorsolateral prefrontal cortex and frontal pole during dual-tasking (both P = 0.003) and stronger frontal and premotor connectivity, which correlated with the performance gains (r = 0.30 to 0.48).
• Both groups did Tai Chi, so the study cannot show what Tai Chi or rTMS does alone; adverse events and effect sizes were not reported, and participants came from one community in China.

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