Abstract
<title>Abstract</title> <p>Background Chronic short sleep worsens cognitive performance and emotional wellbeing, so sleeping more is likely to help. However, many existing interventions are largely educational or advice-based and are not explicitly grounded in behavioural theory or tailored to individual needs. Our personalized intervention for short sleepers -- grounded in the Health Action Process Approach and behavior change techniques, delivered using motivational interviewing -- aims to boost their sleep and cognitive-affective functioning. Methods This single-blind, two-arm randomized controlled trial has a one-week baseline, three-week intervention and a one-month follow-up. We will recruit 210 adults in Hong Kong and randomly assign them to an active control group (n = 70; sleep hygiene only) or an intervention group (n = 150; sleep hygiene plus sleep extension). After baseline monitoring, all participants will receive a week of personalized sleep hygiene guidance. All participants will be asked to maintain sleep hygiene. The intervention group will be asked to sleep for 90 minutes more per night for two weeks, followed by a one-month maintenance period for both groups. Outcome measures include: (a) daily actigraphy and ecological momentary assessment of sleep and cognitive-affective functions; (b) pre- and post-intervention laboratory assessment of sleep architecture and cognitive-affective functions, including vigilance, working memory, planning, and electroencephalography-recorded emotional regulation, and (c) pre- and post-survey responses about sleep, emotional wellbeing, and psychological characteristics (e.g., self-efficacy, motivation). We will analyze these data with multilevel structural equation modeling under both intention-to-treat and as-treated principles. Discussion This study determines whether adding a structured sleep extension component to sleep education further boosts sleep duration and cognitive-affective functions. By combining ecological assessment with laboratory measures, this theory-driven, personalized intervention aims to build a multi-level evidence chain linking behavioral interventions to sleep and cognitive-affective outcomes, hence informing the development of more personalized and scalable sleep health programs. Trial registration : Chinese Clinical Trial Registry, ChiCTR2600116669. Retrospectively registered on January 13, 2026.</p>