Insomnia is prevalent (45%) in CHD patients and associated with significantly increased risk for recurrent cardiovascular events. Insomnia has recently been identified as the third most important risk factor for prognosis. However, very few insomnia patients are identified and receive treatment of insomnia today. CBT-I is the first-line treatment for insomnia, but studies on the effects in CHD patients are lacking. This project aims to document the effectiveness of Cognitive Behavioural therapy for insomnia (CBT-I) in an outpatient population with coronary heart disease (CHD). Furthermore, the biological and psychological mechanisms that may mediate the effects of the intervention will be identified. Finally, a health-economic simulation and a qualitative study of the participants experiences with CBT-I will be performed. This prospective, randomized, intervention study will continue until data have been collected for the primary outcome on 66 CHD outpatients with a diagnosis of insomnia assessed by Bergen Insomnia Scale (BIS). Participants will be randomised to a short, nurse-administered, CBT-I delivered in a group format or to sleep hygiene advice. The primary outcome will be remission from BIS-insomnia post-treatment and at 6-months follow-up. Secondary outcomes will be changes in insomnia severity, objective and subjective sleep parameters, daytime symptoms of insomnia, and quality of life. Exploratory outcomes include inflammation, cortisol, HbA1C, and cognitions/metacognitions. The project may document the effectiveness of CBT-I for a large patient-group with potentially favorable long-term effects on important clinical outcomes.

Inclusion criteria (all the following):

• Aged 18-75 years and signed informed consent and expected cooperation according to ICH/GCP and national/local regulations
• Hospitalised with acute myocardial infarction and/or angiography-verified coronary atherosclerosis, or a coronary revascularisation procedure at Drammen Hospital 2021-2024
• A positive score for insomnia measured with Bergen Insomnia Score
• At least 10 of 14 daily diaries completed of the sleep diary during pre-randomization assessment

Exclusion criteria (any of the following):

• Any condition or situation, that in the investigator's opinion could put the subject at significant risk, confound the study results, interfere significantly with the subject participation in the study, or rendering informed consent unfeasible not limited to:
• Moderate or severe cognitive impairment (i.e. recorded in hospital records or a Montreal Cognitive Assessment brief version score < 11), seizure disorders, active suicidal intent or plans, substance or alcohol dependence, psychotic disease, major depressive disorders or bipolar disorders, receiving concurrent psychological treatments, and ongoing night shift work.
• Neurological or musculoskeletal disorders that restrict movement of the dominant arm because of the possible confounding effects on wrist actigraphy recordings.
• A diagnosis of heart failure recorded in the hospital medical records and/or an NT-proBNP >125 pg/mL
• Short life expectancy (<12 months) due to end-organ (i.e COPD 4, CKD 4/5) or malignant diseases
• Not being able to understand Norwegian.
• No other significant sleep disorder, as assessed via the Structured Clinical Interview for Sleep disorders (Kallestad et al., 2022)
• A clinical diagnosis of Obstructive Sleep Apnea (OSA) (not treated with CPAP) recorded in the hospital medical records, under evaluation for OSA, and/or a score ≥5 on the STOP-Bang OSA screening questionnaire