Small Monetary Incentives for Digital Cognitive Training Adherence in Community-Dwelling Older Adults

Participants receive digital cognitive training only, with no monetary incentive. They are asked to complete daily cognitive training tasks using the mobile app for about 15-20 minutes per day during the 12-week intervention period. Training completion is recorded automatically by the app.

Participants complete daily cognitive training tasks via a mobile application ("Memory Fitness Coach," developed by Changsha Wuwangwo Education Technology Co., Ltd.) for approximately 15-20 minutes per day. The tasks target attention, memory, executive function, and processing speed. Task difficulty is automatically adjusted to maintain an accuracy level of approximately 80%. Training is performed at home using the participant's own smartphone. All participants, including those in the control group, receive this intervention during Weeks 2-13.

Participants receive digital cognitive training plus a daily monetary incentive of up to 0.2 CNY. After completing all prescribed daily training tasks, they earn a reward proportional to their accuracy (e.g., 0.2 CNY × accuracy). Rewards are credited daily to the app account and can be withdrawn at any time.

Participants complete daily cognitive training tasks via a mobile application ("Memory Fitness Coach," developed by Changsha Wuwangwo Education Technology Co., Ltd.) for approximately 15-20 minutes per day. The tasks target attention, memory, executive function, and processing speed. Task difficulty is automatically adjusted to maintain an accuracy level of approximately 80%. Training is performed at home using the participant's own smartphone. All participants, including those in the control group, receive this intervention during Weeks 2-13.

Participants in this arm receive the same digital cognitive training as the control group, plus a daily monetary reward of up to 0.2 CNY after completing the daily cognitive training session. The actual reward is proportional to accuracy (e.g., 0.2 CNY × accuracy). Rewards are credited daily to the app account and can be withdrawn at any time. This incentive is provided only during the 12-week intervention period (Weeks 2-13).

Participants receive digital cognitive training plus a daily monetary incentive of up to 0.5 CNY. After completing all prescribed daily training tasks, they earn a reward proportional to their accuracy (e.g., 0.5 CNY × accuracy). Rewards are credited daily to the app account and can be withdrawn at any time.

Participants complete daily cognitive training tasks via a mobile application ("Memory Fitness Coach," developed by Changsha Wuwangwo Education Technology Co., Ltd.) for approximately 15-20 minutes per day. The tasks target attention, memory, executive function, and processing speed. Task difficulty is automatically adjusted to maintain an accuracy level of approximately 80%. Training is performed at home using the participant's own smartphone. All participants, including those in the control group, receive this intervention during Weeks 2-13.

Participants in this arm receive the same digital cognitive training as the control group, plus a daily monetary reward of up to 0.5 CNY after completing the daily cognitive training session. The actual reward is proportional to accuracy (e.g., 0.5 CNY × accuracy). Rewards are credited daily to the app account and can be withdrawn at any time. This incentive is provided only during the 12-week intervention period (Weeks 2-13).

Participants receive digital cognitive training plus a daily monetary incentive of up to 1 CNY. After completing all prescribed daily training tasks, they earn a reward proportional to their accuracy (e.g., 1 CNY × accuracy). Rewards are credited daily to the app account and can be withdrawn at any time.

Participants complete daily cognitive training tasks via a mobile application ("Memory Fitness Coach," developed by Changsha Wuwangwo Education Technology Co., Ltd.) for approximately 15-20 minutes per day. The tasks target attention, memory, executive function, and processing speed. Task difficulty is automatically adjusted to maintain an accuracy level of approximately 80%. Training is performed at home using the participant's own smartphone. All participants, including those in the control group, receive this intervention during Weeks 2-13.

Participants in this arm receive the same digital cognitive training as the control group, plus a daily monetary reward of up to 1 CNY after completing the daily cognitive training session. The actual reward is proportional to accuracy (e.g., 1 CNY × accuracy). Rewards are credited daily to the app account and can be withdrawn at any time. This incentive is provided only during the 12-week intervention period (Weeks 2-13).

The primary outcome is the completion rate of digital cognitive training during the 12-week intervention period (Weeks 2-13, 84 days). Completion rate is defined as the number of days on which all prescribed training tasks were completed divided by 84 days, multiplied by 100%. Participants who withdraw or do not train on a given day are counted as non-adherent, with the denominator remaining 84 days. The primary comparison is between the combined incentive groups and the control group.

Completion rate calculated separately for the run-in period (Week 1, 7 days), intervention period (Weeks 2-13, 84 days), and follow-up period (Weeks 14-17, 28 days). For each stage, completion rate = number of days with all prescribed tasks completed / total days in that stage × 100%.

Participation rate calculated separately for the run-in, intervention, and follow-up periods. Participation rate = number of days with APP login and at least 1 completed training task / total days in that stage × 100%. This distinguishes "starting training" from "completing all tasks".

Average number of training tasks completed per day during the run-in, intervention, and follow-up periods, recorded automatically by the APP. This reflects training dose.

Weekly average number of daily training tasks from Week 1 to Week 17, analyzed using a linear mixed model to assess changes over time and differences between groups. Used to evaluate whether incentive effects decay and how training behavior changes after incentive withdrawal.

Change in MoCA total score from baseline to post-intervention (Week 14). MoCA score ranges from 0 to 30, with higher scores indicating better cognitive function. Administered on-site by trained researchers using a standardized protocol.

Change in DiaMem score from baseline to post-intervention (Week 14). DiaMem score is the mean of three tests (one on-site and two home-based), ranging from 0 to 100. Higher scores indicate better cognitive function.

Proportion of participants in each group with an intervention-period completion rate ≥80%. Numerator: number of participants with completion rate ≥80%; denominator: number of randomized participants who did not withdraw informed consent.

Proportion of older adults in the target community who actively contacted the researcher, underwent preliminary screening, signed informed consent, and successfully downloaded the cognitive training APP. Numerator: number of such participants; denominator: total number of age-eligible (≥60 years) smartphone-using older adults in the community during the same period.

Proportion of participants who passed the 1-week run-in and could independently complete at least 2 days of cognitive training. Numerator: number of such participants; denominator: all participants who signed informed consent and downloaded the APP.

Proportion of participants who completed the 12-week intervention and received the final assessment. Completion of the 12-week intervention is defined as completing at least 1 day of training in each of the 12 weeks. Numerator: number completing and assessed; denominator: total randomized participants.

Total time in minutes spent by researchers on training, answering questions, active contact, and data verification for each participant from enrollment to the end of the intervention period. Used for cost estimation.

Number and proportion of participants experiencing adverse events during the study period. Serious adverse events will be reported promptly to the ethics committee.

User experience with the digital cognitive training app will be assessed at the post-intervention assessment (Week 14) using the Short Version of the User Experience Questionnaire (UEQ-S). The UEQ-S contains 8 items rated on a 7-point semantic differential scale and yields two subscale scores, pragmatic quality and hedonic quality, as well as an overall user experience score. Higher scores indicate more positive user experience. The UEQ-S will be used as an indicator of participant acceptance of and user experience with the training app. Open-ended feedback on the training program and incentive scheme may be collected separately.