Here is the design of a clinical trial:

Official Title: Impact of a Cognitive Intervention Enriched With Leisure Activities on Cognition, Daily Life Functioning and Brain Structure and Function in Persons With Subjective Cognitive Decline: The ENGAGE Program

Included conditions:
- Subjective Cognitive Decline

Study Armgroups:
- {'label': 'ENGAGE SPANISH/MUSIC', 'type': 'EXPERIMENTAL', 'description': 'Cognitive strategies to improve attention and memory skills and application in selected leisure activities (music or Spanish lessons, and videogames) over 4 months.', 'interventionNames': ['Behavioral: ENGAGE SPANISH/MUSIC']}
- {'label': 'ENGAGE DISCOVERY', 'type': 'ACTIVE_COMPARATOR', 'description': 'Educational program about brain and healthy aging complemented by learning of new information with videogames, documentaries and group discussions over 4 months.', 'interventionNames': ['Behavioral: ENGAGE DISCOVERY']}

Interventions:
- {'type': 'BEHAVIORAL', 'name': 'ENGAGE SPANISH/MUSIC', 'description': 'Cognitive strategies to improve attention and memory skills (21 hours), leisure activities (music lessons or Spanish lessons) (27 hours), selected videogames to practice variable attention strategies (4 hours in class + about 10 hours at home). Total of 24 2-hour in class sessions over 4 months. The training will be delivered to small groups of 5 to 8 participants by a trained therapist for formal sessions and a professional music or Spanish teacher for leisure sessions.', 'armGroupLabels': ['ENGAGE SPANISH/MUSIC']}
- {'type': 'BEHAVIORAL', 'name': 'ENGAGE DISCOVERY', 'description': 'Educational content about brain and healthy aging (21 hours), leisure activities (watching documentaries followed by group discussion and debate) (27 hours), selected non-stimulating videogames (4 hours in class + about 10 hours at home). Total of 24 2-hour in class sessions over 4 months. The training will be delivered to small groups of 5 to 8 participants by the same trained therapist as in the ENGAGE arm.', 'armGroupLabels': ['ENGAGE DISCOVERY']}

Primary Outcomes:
- {'measure': 'Changes in episodic memory (composite score)', 'description': "A composite score will be computed by averaging z-scores from the delayed recall of the Rey Auditory Verbal Learning Test (RAVLT) and the delayed recall of the face-name association task (an associative memory test adapted from Simona Brambati's task for the Consortium pour l'Identification precoce de la Maladie d'Alzheimer (CIMA-Q) study currently running in Quebec).", 'timeFrame': 'PRE (within 12 weeks before intervention starts) + POST-1 (within 8 weeks after the end of intervention) + POST-2 (2 years from PRE, +/- 3 months)'}

Please estimate the sample size based on the assumption: 
The power analysis was conducted using G*power, considering an 18% attrition rate, and based on the pilot findings with the MEMO program.
Sample size
          The trial will recruit 144 participants. The sample size was estimated from a power analysis with G*power based on pilot findings collected with the MEMO program [10, 12], using word recall and face-name associations tasks. The MEMO program is included as part of the formal training in this intervention in addition to stimulating leisure activities and attentional training. Therefore, it is reasonable to expect that the effect should be at least as large as the one observed when using MEMO alone. The pilot data indicated a medium effect size for the group-by-time interaction when examining face-name association and a large effect size when examining word recall (see AdditionalÂ fileÂ 2: Appendix 2). It shows that the sample size would be sufficient to detect an interaction given a similar effect size considering the same attrition rate that we obtained in this prior study (18%). Half of the sample will be recruited in Montreal and the other half will be recruited in Toronto.