Understanding the Role of the Locus Coeruleus in Insomnia

This research project aims to better understand the neurobiological mechanistic underpinnings of insomnia disorder. The main question is whether cortical hyperarousal in individuals with insomnia disorder, measured by electroencephalograhic (EEG) infraslow oscillation coupling of sigma power during non-rapid eye movement (NREM) sleep and theta power during rapid eye movement (REM) sleep, is related to locus coeruleus activity.

This trial is a double-blinded, placebo-controlled, randomised controlled cross over trial of dexmedetomidine or placebo in adults with insomnia disorder. Participants will be recruited using social media, bulletin boards and patient referrals from the Woolcock Institute of Medical Research clinics. Participants will be asked to complete an online pre-screening webpage (RedCap) to check for eligibility, and provided with the Participant Information Sheet (PIS) and asked for contact details for an in-person screening visit. The participants will have the study explained in detail during the screening visit followed by written informed consent. The participant will then undergo a medical screening for diagnosis of insomnia disorder and the medical officer will sign the consent form. Thereafter, the participant will complete baseline questionnaires and be randomised to either dexmedetomidine or placebo for the 2 sleep laboratory visits. Participants will then be instructed to maintain their regular sleep-wake patterns for seven days before the first sleep laboratory visit (Visit 1). During Visit 1, participants will undergo a number of assessments (pre-sleep locus coeruleus activity measured using pupillometry, electroencephalography (EEG), functional near-infrared spectroscopy (fNIRS) before and during sleep and questionnaires about subjective hyperarousal. Participants will receive either dexmedetomidine or placebo. Following Visit 1, participants will have a 14-day washout, before Visit 2, which will repeat the procedures of Visit 1, but participants will receive the alternate condition (placebo or dexmedetomidine). The study will be coordinated from the Woolcock Institute of Medical Research, Sydney, Macquarie University, NSW, 2113, Australia.