Chronic pain is a common health problem among older adults and their informal caregivers. Chronic pain has negative effects on physical and psychological health status and it is a strong predictor of poor quality of life. In this study, a dyadic face-to-face pain management program will be provided to older adults and informal caregivers to help the dyads equip with pain-related knowledge and pain coping skills. The effectiveness of the dyadic program will be assessed. Participants will be recruited follow snowball sampling and will be randomly allocated to experimental group and control group using 1: 1 radio. The dyadic pain management program will last four weeks, including group discussion, pain-related knowledge and physical exercises. Pain intensity, anxiety, depression, stress, pain self-efficacy and quality of life will be measured in baseline, post-treatment and at one-month follow. Acceptability and satisfaction to the program will be collected.

This study will be held in Caritas District Elderly Centre-Yeun Long (Tin Chak Centre) and Caritas Cheng Shing Fung District Elderly Center (Shamshuipo) in Hong Kong. For sample size, no suitable standard deviation and effect size was found in previous similar study through the literature review, so this study will be a pilot RCT study with a total 60 dyads of sample size. 30 older adults and 30 informal caregivers will be in each group (experimental group and control group). The dyadic pain management program will be held in the community activity center at weekends and will involve three parts: demographic data, outcome measures (baseline, post-treatment and one-month follow-up measures) and pain education.

Potential participants' eligibility will be confirmed by a questionnaire designed according to inclusion criteria and exclusion criteria. An information sheet will be provided to the eligible dyads and informed consent will be signed on the scene. Experimental group will start pain management program when finish the baseline assessment and control group will be given one page of pain management information download from Department of Health. (http://www.elderly.gov.hk/english/common\_health\_problems/bones\_and\_joints/index.html). For optimal communication, two WhatsApp groups will be created consisting of all the caregivers in experimental group and control group respectively.

Outcomes will be measured at three times during the whole intervention, T0 baseline prior to intervention, T1 in week four when the experimental group finish all the program and T2 in week eight with one-month follow-up after the program. Dyads' demographic and caregiving-related questions will be completed prior to beginning the program in T0. Pain related situations, anxiety, depression, stress, quality of life, pain self-efficacy will be measured from older adults and informal caregivers at T0, T1, T2, using a same battery of questionnaires. Dyads' acceptability and satisfaction will be administered immediately after the last session. Data will be collected by a research assistant blinded to the dyads' group assignments.

Participants

This study is a dyadic intervention. Target populations are older adults and informal caregivers with chronic pain. A pair of informal caregiver and older adult will be regarded as a dyad. Dyads will be recruited in the community following the snowball sampling, the eligibility will be accessed based on the following details:

Older adults

Inclusion criteria for older adults:

1. Aged 65 or above;
2. Have an informal caregiver willing to participate this program;
3. Can understand Chinese;
4. Have a history of non-cancer pain in past 6 months;
5. Pain score should be at least 2 measured by Numeric Rating Scale, a 11-point numeric scale ;
6. Have behavioral abilities to do a light exercise and stretch program;
7. Able to attend the whole sessions in community activity center.

Exclusion criteria for older adults:

1. Have serious organic disease or malignant tumor;
2. Have a history of consciousness or mental disorder diagnosed by neurologists or psychiatrists;
3. Have a further medical/surgical treatment in two months or have joined in other pain management program.
4. Experience a drug addiction problem

Informal caregivers Inclusion criteria for informal caregivers

1. Aged 18 or above;
2. As an informal caregiver for one older adult;
3. Can understand Chinese;
4. Have a history of non-cancer pain in past 6 months;
5. Pain score should be at least 2 measured by Numeric Rating Scale, a 11-point numeric scale ;
6. Own a smartphone and can assess the internet;
7. Able to attend the whole sessions in community activity center.

Exclusion criteria for informal caregivers

1. Have serious organic disease or malignant tumor;
2. Have a history of consciousness or mental disorder diagnosed by neurologists or psychiatrists;
3. Have a further medical/surgical treatment in two months or have joined in other pain management program.
4. Experience a drug addiction problem

Outcome measures It is a dyadic intervention so outcomes will be measured from older adults and informal caregivers.

Primary outcome The Brief Pain Inventory-Chinese Version It is a tool to evaluate the intensity, site, quality, relief, interference and causes of pain in patients. Four items for the degree of pain severity, one item for the degree of pain relief and seven items for degree of pain interferes will assess, numbering the different pain sites from 0 to 10. For BPI-C, the Cronbach's α for the pain severity and pain interference items are 0.83-0.89 and 0.90-0.91 and has good acceptable test-retest reliability .

Secondary outcomes:

World Health Organization Quality of Life-Brief It is a self-report questionnaire which assesses 4 domains of quality of life, including physical health, psychological health, social relationships, and environment. Participants will express how much they have experienced in the preceding two weeks on a 5-point Likert scale ranging from 1 (not at all) to 5 (completely). Previous studies showed that WHOQOL-BRIF has good internal consistency and validity.

Depression Anxiety Stress Scale It is a self-administered psychological instrument to evaluate the degree of depression, anxiety and stress involving 21 items. Every part has seven items on a 4-point Likert scale ranging from 0 to 3. The instrument was used in previous studies and had good internal consistency and validity.

Pain Self-efficacy Questionnaire It is a tool to measure the self-efficacy in coping with daily activities with pain . A Chinese version of the PSEQ will be used in this study. Participants will express participants' confidence in performing ten activities experiencing pain on a 7-point Likert scale ranging from 0 (not at all confident) to 6 (completely cinfident). Previous studies illustrated the test-rest reliability coefficient of PSEQ was 0.75 and internal consistency, Cronbach's alpha was 0.95, which was reliable .

Satisfaction and acceptability Participants' satisfaction and acceptability of the dyadic intervention will be assessed at the end of the grogram. Some open-ended questions will be asked, including "What topics, content, or concepts could have been covered in more/less detail?" "As a result of participating in dyadic pain management intervention, did you make some positive changes in your life?" "Would you feel the group discussions interesting and informative? Did the activities and exercises relieve your pain symptom?" These questions were used in previous studies to evaluate the satisfaction and acceptability of intervention program.

Inclusion Criteria:

For Older adults:

1. Aged 65 or above;
2. Have an informal caregiver willing to participate this program;
3. Can understand Chinese;
4. Have a history of non-cancer pain in past 6 months;
5. Pain score should be at least 2 measured by Numeric Rating Scale, a 11-point numeric scale;
6. Have behavioral abilities to do a light exercise and stretch program;
7. Able to attend the whole sessions in community activity center.

For Informal caregivers:

1. Aged 18 or above;
2. As an informal caregiver for one older adult;
3. Can understand Chinese;
4. Have a history of non-cancer pain in past 6 months;
5. Pain score should be at least 2 measured by Numeric Rating Scale, a 11-point numeric scale;
6. Own a smartphone and can assess the internet;
7. Able to attend the whole sessions in community activity center.

Exclusion Criteria:

For Older adults:

1. Have serious organic disease or malignant tumor;
2. Have a history of consciousness or mental disorder diagnosed by neurologists or psychiatrists;
3. Have a further medical/surgical treatment in two months or have joined in other pain management program.
4. Experience a drug addiction problem.

For Informal caregivers:

1. Have serious organic disease or malignant tumor;
2. Have a history of consciousness or mental disorder diagnosed by neurologists or psychiatrists;
3. Have a further medical/surgical treatment in two months or have joined in other pain management program.
4. Experience a drug addiction problem.