The Effects of Tai Chi on Cognition and Instrumental Activities of Daily Living, and Health Related Quality of Life in Older People With Mild Cognitive Impairment .

1. Study design & sample recruitment:

This was a quasi-experimental study which adopted the multi-site non-randomized control group pre- and post-test design. By adopting the multi-site design, better representation of the population could be obtained. This intervention study involved two groups of participant, the experimental and control groups, whereas no randomization would be taken place.

The study was carried out in District Elderly Community Centers (DECCs) in Hong Kong. The DECC has been implemented since 2001 under the support from the Social Warfare Department (SWD) to provide community support services at district level to enable older people to remain in the community and to lead a healthy, respectful and dignified life.The service users are community-dwelling older citizens aged 60 or above living in the locality. Invitation letters were sent to various DECCs for joining the study. Finally, there were four elderly centers willing to participate in the study. The participants were recruited from the four DECCs using convenience sampling.

To avoid the possible diffusion effect that might interfere the research result, all eligible participants in a community center were allocated to either experimental group or control group, who were treated with single intervention, so there would be no discussion among participants who have received different treatment regimes.

The present study had employed a control group to enhance methodological rigor and included a pre-test to assess the equivalence between two groups, so the problem on selection biases could be alleviated. 2. Sample size estimation A medium effect size of 0.5 was set for the study, based on previous research on the effect of Tai Chi on cognitive function. Based on the use of a sample size calculator (https://www2.ccrb.cuhk.edu.hk/stat/Other.htm), a sample of 64 per group was expected to provide 80% power to detect a medium effect size of 0.5, at a significance level of 0.05. Allowing for an attrition rate of 20% in the Tai Chi groups, 80 participants were recruited for each group. 3. Intervention The intervention group received a 16-week Tai Chi program, of 32 sessions (two sessions per week) each one hour long.The capacity was around 20 people per class. A certified Tai Chi master taught the Yang-style simple form of Tai Chi to the participants allocated to the experimental group.There were four sets of movements included in the simplified form; this required less time for the older practitioners, who usually had less exercise endurance, to complete the whole set of movements. Moreover, it was an appropriate form of Tai Chi for older people with MCI because it involved only a few postures, hence it was easier for them to learn and remember. The Tai Chi classes were conducted in the open hall of the community center or a public playground with sufficient space, a flat floor and good lighting.To promote safety, measures include appropriate footwear, appropriate warm-up and cool-down, correct exercise technique and gradual increases in exercise dose will be emphasized in Tai Chi class. Incident report will be done to record and analyses causes for any adverse effect on Tai Chi training.To ensure adherence, the participants were required to sign attendance records. Telephone follow-up was arranged to provide emotional support and reinforce compliance if they were absent from two consecutive lessons. As well, the participants were advised to do daily practice at home to foster better mastery of the Tai Chi movements and build up a regular exercise habit. A guide book was issued to each participant, providing guidance to reinforce correct postures.