Insomnia is a prevalent sleep disorder associated with numerous adverse health outcomes, including fatigue, irritability, and impaired daytime functioning. Despite the availability of effective pharmacological and psychological treatments, relatively few individuals with insomnia seek professional help, highlighting the need for accessible and acceptable non-pharmacological interventions. Sleep hygiene education (SHE) has the potential to address this gap due to its simplicity, low cost, and ease of self-administration. Building on our previously registered pilot-testing protocol, this study aims to examine the effectiveness of a theory-based SHE program integrated with behavior change techniques in a larger community population. Furthermore, it remains unclear whether theory-based SHE is inferior to gold-standard interventions such as cognitive behavioral therapy for insomnia (CBT-I) delivered via digital applications. Therefore, this study will also compare the effectiveness of theory-based SHE with a CBT-I app using a three-arm randomized controlled trial design.

Insomnia is a prevalent sleep disorder associated with substantial adverse health consequences, including fatigue, irritability, and impaired daytime functioning. Although effective pharmacological (e.g., hypnotics) and psychological treatments (e.g., cognitive behavioral therapy for insomnia, CBT-I) are available, both local and international surveys indicate that fewer than 50% of individuals with insomnia seek treatment. This treatment gap underscores the need for effective non-pharmacological interventions that are both accessible and acceptable.

Sleep hygiene education (SHE) represents a potentially suitable approach to address this unmet need. SHE is an educational intervention encompassing a range of lifestyle and environmental recommendations to optimize sleep quality and duration. These include maintaining a regular sleep-wake schedule, avoiding substances such as caffeine, nicotine, and alcohol, limiting daytime napping and stimulating activities before bedtime, optimizing the sleep environment, and adopting appropriate dietary and exercise habits etc. Given its simplicity, low cost, accessibility, and ease of delivery and adoption, SHE holds promise as a non-pharmacological strategy for insomnia management.

Despite these advantages, SHE is not typically recommended as a stand-alone treatment for individuals with sleep problems, as it is often perceived to be less effective than CBT-I or mindfulness-based interventions, with consistently small effect sizes reported. However, these findings should be interpreted with caution. In many previous studies, SHE has primarily been used as a passive control condition to account for nonspecific treatment effects, thereby underexploiting its active therapeutic potential. Moving SHE beyond a simple advice-giving modality to a structured, theory-informed approach may optimize its effectiveness by ensuring its content is informative and promising. Integrating SHE with established behavior change techniques may better equip individuals with the skills needed to initiate and sustain meaningful behavioral change.

Building on our previously registered pilot-testing protocol, this study aims to evaluate the effectiveness of a theory-based SHE program integrated with behavior change techniques in a larger community sample. In addition, it remains unclear whether theory-based SHE is inferior to gold-standard interventions such as digitally delivered CBT-I. This study will also examine whether a theory-based SHE program is a cost-effective approach for reducing insomnia severity in adults with insomnia disorder compared with a CBT-I app and a no-intervention control. To address these objectives, a three-arm randomized controlled trial will be conducted to compare the relative effectiveness of these interventions.

Inclusion Criteria:

• Hong Kong residents
• Ethnic Chinese aged 18-65 years with the ability to communicate in Cantonese or Putonghua
• Who fulfil the DSM-5 diagnostic criteria for insomnia disorder according to a validated diagnostic tool, the Brief Insomnia Questionnaire
• Scored at least 10 points in the Insomnia Severity Index
• Willing to give informed consent

Exclusion Criteria:

• Any current diagnosis fulfilling the DSM-IV criteria of a major depressive disorder, generalized anxiety disorders, post-traumatic stress disorder, panic disorder, substance use disorders, or schizophrenia as screened using the Chinese version of the Structured Clinical Interview for DSM-IV
• Other sleep disorders, including circadian rhythm disorder, narcolepsy, obstructive sleep apnoea (OSA), and restless leg syndrome (RLS)/periodic leg movement disorder (PLMD) as determined based on cut-off scores (≥ 7 on narcolepsy; ≥ 8 on circadian rhythm disorder; ≥ 15 on OSA; ≥ 7 on RLS/PLMD) using SLEEP-50. If in doubt, subjects will be referred to our team psychiatrist (KF Chung) for further assessment
• Any current medical conditions or side-effects of medication that are contributing significantly to the subject's insomnia
• Taking medications or currently participating in other psychotherapies for insomnia or other psychiatric disorders
• Impaired cognitive functioning (<22 points in HK-MoCA) or with difficulty in giving consent or understanding instructions
• Pregnant
• Shift work