The JITAI approach holds considerable promise for addressing current challenges in mHealth, including the limitations in supporting real-time monitoring, timely intervention, and poor adherence. However, research on JITAIs in the field of behavioural sleep medicine is still in its infancy. Leveraging existing pilot data, this project will entail a micro-randomised trial (MRT) designed to optimise the JITAI components and a randomised controlled trial (RCT) to examine the efficacy of the optimised JITAI on sleep and circadian functions. Specifically, research has indicated that contextually tailored suggestions are more effective in promoting health behaviors compared to generic messages. This study will include personalised, in-the-moment actionable suggestions based on the Transdiagnostic Intervention for Sleep and Circadian Dysfunction (TranS-C) to evaluate their efficacy in contrast to generic messages and no notifications.

The proposed project will have three phases. Phase I will be the technological advancement of the JITAI app, GoodShleep. Based on research findings, additional intervention engagement strategies will be added to improve adherence, including personalisation (i.e., personalised feedback and intervention content), gamification (i.e., goal setting and rewards for a completed mission), and reminders (i.e., push notifications). The refined app will be beta-tested by the research team and five individuals experiencing sleep or circadian problems to ensure the app's functionality and usability. Issues that may arise during Phase I will be resolved prior to commencing Phase II.

Phase II will be an MRT aiming to optimise the advanced GoodShleep alongside wearable devices and ecological momentary assessment (EMA). A total of 77 participants with sleep or circadian problems will participate in the JITAI through the advanced GoodShleep, which will comprise (1) an 8-week, smartphone-based JITAI on TranS-C; (2) EMA prompted by push notifications to detect sleep-wake regularity and mood status; and (3) 24-hour real-time wearables assessing sleep and activity. Participants will be randomly assigned to receive contextually personalised suggestions, generic messages, and no notifications based on our micro-randomised algorithm.

Phase III will involve an RCT to evaluate the optimised JITAI app, GoodShleep + in both short- (immediately after intervention) and medium-term (12 weeks after intervention). Eighty participants with sleep and circadian problems will be randomised into the optimised JITAI (GoodShleep+) and the care-as-usual (CAU) group in a 1:1 allocation ratio. The JITAI (GoodShleep) will be adjusted and finalised based on the findings from Phase II to transform into the optimised JITAI (GoodShleep+). The GoodShleep+ group will receive an 8-week, smartphone-based GoodShleep+ based on TranS-C. The CAU group will not receive the GoodShleep+ but will have access to usual care based on their needs and preferences. The CAU group will receive GoodShleep+ after completing all the assessments. Major assessments will be conducted at baseline, immediate post-intervention and 12-week follow-up. Participants' sleep conditions will be evaluated using the brief consensus sleep diary and wearables. Activity levels will be measured using wearables at multiple time points. Mood status will be assessed using selected items from PANAS-SF. Participants' weekly sleep and circadian functions will be monitored using Patient-Reported Outcomes Measurement Information System (PROMIS) Sleep Disturbance (SD) and Sleep-Related Impairment (SRI). Other outcomes will include sleep quality, anxiety and depression symptoms, sleep-related cognitions, overall daytime sleepiness, fatigue, quality of life and functional impairment. Intervention acceptability and intervention adherence will also be assessed.

The current registration is only for Phase I and II of the current research project.

Inclusion Criteria:

• Adults aged 18 to 65 years living in Hong Kong
• Chinese language fluency and literacy
• Experiencing ≥1 sleep or circadian problems for 3 months based on the Sleep and Circadian Problems Interview, an adapted version of the Insomnia Interview Schedule (i.e., time needed to fall asleep ≥30 minutes for ≥3 nights per week, wake after sleep onset ≥30 minutes for ≥3 nights per week, <6-hour sleep per night or ≥9-hour sleep per night per 24hour period for ≥3 nights per week, variability in the sleepweek schedule ≥2.78 hours within a week, and falling asleep after 2:00 AM on ≥3 nights per week)
• One or more PROMIS-Sleep Disturbance (PROMIS-SD) item scores ≥4 after reverse scoring
• Having adequate opportunity and circumstances for sleep to occur
• Installing the JITAI app in an Internet-enabled mobile device (iOS or Android operating system)
• Are willing to provide informed consent and comply with the trial protocol

Exclusion Criteria:

• Involving in any psychological treatment for sleep disturbances in the past 6 months
• Self-report of a significant untreated severe mental illness (e.g., bipolar disorder, psychotic disorder)
• Presence of medical or cognitive disorder(s), or side effects of medication that contribute significantly to sleep or circadian problems or make participation challenging based on the team's clinical judgement
• Working night shift (>2 nights per week) in the past 3 weeks (i.e., regularly scheduled work from 12AM to 6AM)
• Pregnancy or breastfeeding
• Having a medical or psychiatric condition where sleep restriction is deemed unsuitable due to potential worsening of the condition.

Other Criteria:

• Individuals who have sleep apnoea or periodic limb movement disorder commonly experience co-occurring insomnia will be included in the study due to the potential benefits they may derive from TranS-C
• To allow for greater generalisability, this study will not exclude those with mental disorders whose conditions are stable based on the research team's judgement
• If serious suicidal risk (i.e., Patient Health Questionnaire Item 9 score >2) is identified, the participant will be referred to the PA (a clinical psychologist) for further assessment and professional mental health services, if needed
• Medication use and changes will be recorded.

The participants and outcomes assessor will also be blinded during the micro-randomization.