Effectiveness of Cognitive Stimulation Therapy Group for Residential Home Residents With Dementia and Mild Cognitive Impairment-- A Randomized Controlled Trial

The research aims to investigate the effectiveness CST group for residential home residents with dementia and MCI. Additionally, the underlying mechanism of change of CST group will also be investigated.

Hypotheses.

1. The CST group is effective in improving cognitive abilities, depressive symptoms, engagement, social interaction and quality of life compared to the control group after the intervention.
2. The positive intervention results of the CST group are maintained at the 3-month follow-up
3. Improvement in cognitive ability is predicted by improved engagement in group activities.

Research Design. This study adopts a multicentre randomized control trial research design, involving 110 older people with dementia and MCI recruited from residential homes of SAGE. Using cluster randomization, participants will be openly recruited into activity groups in residential homes for older adults. The activity groups will then be randomly assigned to the intervention or control group in a 1:1 ratio. The intervention group will receive a 14-session CST group, while the control group will receive a calligraphy group. A research staff, who does not involve in the group allocation and group intervention, conduct the intervention outcomes assessment of the participants before and after the intervention and 3-months follow-up. Standardized assessment tools are used to assess the intervention outcomes, including cognitive functions, depression, quality of life, and engagement and social functioning. The ethical considerations of this study will be reviewed and approved by the Research Committee of the City University of Hong Kong. Data collection will begin in January 2026 and be completed in August 2026.

Subject Inclusion Criteria:

1. age 60 years or older;
2. diagnosis of MCI or dementia according to the Diagnostic and Statistical Manual of Mental Disorder (Fifth edition, Text Revision); Participants who do not receive a diagnosis of MCI or dementia will undergo a screening assessment by a researcher using the Chinese Montreal Cognitive Assessment (MoCA)-5 minutes.

Subject Exclusion Criteria Those who are unable to participate independently in group activities, who exhibit disruptive behavior and/or are severely impaired by physical disabilities (e.g. severe hearing and visual impairment) and physical illnesses (e.g. frequent hospital stays) are excluded.

Sample size estimation. The sample size of this study is estimated by using power analysis G*Power 3.1. Recent studies on CST suggest a medium to large effect size on improving cognitive function. This study aims to detect a medium effect size (i.e., Cohen's d = 0.40) with a statistical power of 0.80 for all intervention outcomes and with a dropout rate of 20%, 110 people with dementia will be recruited in this study.

Intervention and Control Group Activities. The participants are randomly assigned to an intervention group or a control group. The intervention group receives the Cognitive Simulation Therapy (CST) group, while the control group receives the calligraphy group.

The CST group provides weekly mental stimulation activities on a specific topic as mentioned above. It consists of a total of 14 sessions with two sessions per week, each lasting approximately 45 minutes and led by an occupational therapist. CST group consists of 14 sessions, with each session focusing on a theme, including: reality orientation, childhood, physical games, food, sound, faces, number games, word association, word games, current events, categorizing objects, using money, being creative, and team games. The stimulating activities are designed to match the abilities and interests of participants.

The Calligraphy group provides weekly calligraphy activities. It consists of a total of 14 sessions with two sessions per week, each lasting approximately 45 minutes and led by a rehabilitation assistant under the supervision of an occupational therapist.

Outcomes Assessment Tools The primary intervention outcome of this study is the improvement of cognitive ability as measured by the Chinese Alzheimer's Disease Assessment Scale-Cognitive Subscale (ADAS-Cog) and the Chinese Montreal Cognitive Assessment (MoCA), which have been used as outcome assessment in previous studies of Chinese older adults with MCI.

The secondary intervention outcomes of this study are the improvement in depressive symptoms, engagement, social interaction and quality of life which are assessed by the following standardized scales.

• The Chinese Cornell Scale for Depression in Dementia (CSDD) is a 19-item scale for assessing the mood changes in older adults with dementia and MCI rated by the caregivers.
• The Chinese Quality of Life-Alzheimer's disease (QoL-AD) is a 13item scale for assessing the QoL in older adults with dementia and MCI. In this study, QoL-AD is completed by both older adults with dementia and MCI as well as their caregivers independently to give self-rated and caregiver-rated QoL.
• The Engagement of a person with dementia scale (EPWDS) is a 10-item scale to assess five areas of engagement in in older adults with dementia and MCI, including affect, visual, verbal, behavioural and social, rated by the caregivers.
• The Chinese Social Functioning in Dementia scale (SF-DEM) is a 20-item scale for assessing social interactions with family, friends, and the community in older adults with dementia and MCI. In the present study, the SF-DEM is completed by both older adults with dementia and MCI as well as their caregivers independently to give self-rated and caregiver-rated social functioning.
• The Clinical Sustainability Assessment Tool (CSAT) is a 35-item scale for assessing the sustainability of clinical practices for the intervention group. This scale is rated by management and professional staff of SAGE residential homes.

Data Analyses. The analysis is carried out according to the intent-to-treat principle, whereby the multiple imputation method is used for missing data. The data analyses are performed with SPSS 29.0. Within-group intervention effects will be analyzed for all intervention groups using repeated measures one-way analysis of variance (ANOVA). Between group intervention effects are analyzed using 2 (group) x 2 (time) repeated measures of ANOVA. Within and between group effect sizes are computed using Cohen's d, with values of 0.2, 0.5, and 0.8 considered as small, medium, and large respectively.

Fidelity of intervention. Standardized program manuals for CST group and calligraphy group will be designed by the research team to suit the needs and interests of participants with dementia and MCI. The occupational therapists conducting the CST group have completed training on conducting CST group. In addition, they receive the standardized program manuals, training and regular supervision, as well as a surprise check from the research team when conducting the CST group to ensure that the interventions implemented by the occupational therapists meet the guidelines and skills of the standardized program manuals. The rehabilitation assistant conducting the calligraphy group will receive the standardized program manuals, training and regular supervision by an occupational therapist to ensure that the interventions conducted by rehabilitation assistant meet the guidelines and skills of the standardized program manuals.

Ethical Considerations. The ethical aspects of this study were reviewed and approved by the Research Committee of the City University of Hong Kong [Reference No.: HU-STA-00001945]. Written informed consent will be obtained from all participants and their guardians on the day of the screening before participants start receiving the intervention.