Background: The growing number of older people with dementia increases demand on informal caregivers who lack information and skills, leading to a high psychological burden in care provision. The proposed smartphone app-based intervention will provide a convenient and feasible solution for reducing depression, stress, and anxiety among dementia carers in Vietnam. This study aims to: (1) understanding the information and skills required by informal carers to populate the content of the intervention and (2) test the clinical feasibility of the intervention and feasibility of a fully- power randomized controlled trial.

Methods: The setting of this study is the geriatrics department in Gia Dinh People's hospital in Ho Chi Minh City. The eligible participants are the informal caregivers of patients with dementia living in the community, who use smartphones. Phase 1 will involve 20 interviews, conducted with 20 dementia carers to determine what information and skills they need most. These findings will be used to design the content of the intervention, which will comprise 8 weekly, online, psycho-educational, group sessions hosted on the Zalo app. Phase 2: using a pilot randomized control trial design, 60 participants will be assigned to the intervention or control group by the block randomization method with a ratio of 1:1. The participants will complete questionnaires at baseline, post-intervention and 3 month post-intervention. Outcome measures include DASS21 (Depression, anxiety and stress 21), dementia understanding, perceived social support, and caregiver's perceived burden. The primary outcome is the feasibility of the intervention and a future fully-power randomized controlled trial including acceptability and perceived effectiveness of the intervention and the rate of recruitment, retention, and completion of assessments.

The study has two phases: the co-design of the content of the intervention (phase 1) and the randomized controlled trial phase (phase 2). The setting and the participants' eligibility criteria are the same for the two phases.

Phase 1 Design: a qualitative study will be conducted on 20 caregivers of patients with dementia to identify what information they most require.

Method: 20 face-to-face interviews will be held and guided by a trained geriatrician, in a private room in the geriatrics department. The open-ended questions are used, including "what difficulties are the participant facing in taking care of the patient with dementia?", "what information do the participant need most?". Each participant will be free to share thoughts. The interviews will be audio-recorded and fully transcribed.

Data analysis: The investigator will use inductive thematic content analysis. The eight most common issues in which the carers need providing information will be determined to shape for the intervention in phase 2.

Phase 2 Study design A parallel-group randomized controlled pilot trial will be used with equal randomization of 1:1 to test the feasibility and the acceptability of the smartphone app-based intervention. Sixty dementia carers, who meet the eligible criteria and are provided written informed consent, will be enrolled in the study and will be allocated to the intervention or usual care group.

Randomization The eligible participants will be assigned to the intervention or control group by an independent statistician, using the block randomization method (blocks of 4).

Intervention The participants in the intervention group will be added to a chat room in the Zalo app, created and managed by one investigator, which is named The Dementia Caregiver Support group. Weekly, the investigator will post one of the eight topics identified in Phase 1. Before posting the information, the investigator will ask the participants what topic they would like to read and discuss the week after by voting the answer. The posted information will be based on evidence-based resources and consulted by geriatricians, the neurologist, and the psychologist who specialize in dementia. Immediately after posting the topic, one investigator will call the participants to ensure the participants read and understand the post. The chat group monitor will also collect the questions or comments from the carers who are encouraged to share feelings or experiences with relevant questions. Then the investigator will post the answers after consulting with the experts.

Usual care: The participants in the control group will be introduced to the website Alzheimer.org to search for eligible information Procedure The characteristics of the participants (age, gender, educational level, relationship to the care recipient, time of care, etc.) and other assessments will be collected by an independent investigator, who will be blinded through the study.

Measures The participants will perform the Depression, anxiety and stress scale 21 (DASS21) questionnaire via phone call interviews. DASS21 scale contains 21 items, evaluating 3 subscales including depression, anxiety, and stress states over the past week. Higher scores indicate more severity of emotional states. Dementia understanding of the participants will be evaluated at baseline and post-intervention by a questionnaire, originating from the Northern Ireland Life and Time Survey, which was translated into Vietnamese. This questionnaire contains 7 items, for example, "dementia is a normal part of aging" or "dementia can be cured". The response options will be completed with yes/no choices. Four or fewer correct answers will be coded as low understanding, five correct answers medium understanding, and six or more answers as high understanding.

Perceived social support will be assessed using the Multidimensional Scale of Perceived Social Support (MSPSS), comprising 12 self-report items assessing the perceived support from family, friends, or significant others (eg, "There is a person who is around me when I am in need). Each item is scored from 1 (very strongly disagree) to 7 (very strongly agree), based on a 7-point Likert scale. Higher scores indicate higher degrees of perceived social support. This scale will be translated and adapted into Vietnamese.

The caregiver's perceived burden will be evaluated usingthe Zarit 4-item burden interview. Each item is scored from 0 to 4, and higher scores indicate higher levels of burden.

Outcome measurements will be assessed face-to-face at baseline and via phone calls at immediate post-intervention and 3-month follow-up post-intervention.

Inclusion Criteria:

• Being the primary caregivers of patients with dementia for at least the past 6 months and will continue to be for the next 6 months of the intervention. Dementia patients are those who have been diagnosed with dementia for at least 6 months and are living in the community.
• Being able to read and understand Vietnamese (at least primary education), and willing to participate in the study.
• Having a smartphone that has the Zalo app or willing to have this Zalo app be installed (there will be short training of using Zalo for new users)
• Aged ≥ 18 years

Exclusion Criteria:

• Having any acute diseases or cognitive impairment (screening by Mini-Cog),
• Having vision or hearing impairment

Share the results of the study

10 months

In Phase 1, participants participated solely in qualitative interviews to describe their experiences and did not receive any intervention. As no intervention or experimental procedures were administered, there was no potential for harm or adverse events in this phase.

The investigator who interview the participants will be blinded during the study.