Impact of Suvorexant on Sympathetic Nerve Activity and Baroreflex Function in Chronic Insomnia

Inclusion Criteria:

• Minimum 3 months of clinically diagnosed insomnia
• Body mass index ≤35 kg/m2
• Insomnia Severity Index (ISI) > 7 arbitrary units (i.e., mild-to-severe insomnia)
• Pre-menopausal women must have regular menstrual cycles (~26-30 day cycles) and willbe scheduled for microneurography 2-7 days after menstruation to consistently testduring the early follicular phase (or low-hormone phase in women on contraceptives)

Exclusion Criteria:

• Current or prior treatment of Suvorexant.
• Obstructive sleep apnea defined as an apnea-hypopnea index > 30 using an FDA approvedhome sleep apnea screening devices as used in routine clinical practice.
• Participants without evidence of clinically significant obstructive sleep apnea on thescreening test will undergo an overnight in-laboratory polysomnography to confirmabsence of sleep apnea (apnea-hypopnea index of ≥ 30 episodes per hour) and to excludeother sleep disorders (e.g. periodic limb movement arousal index of ≥ 5 episodes perhour)
• Circadian rhythm sleep disorders
• History of meeting DSM-V criteria of major psychiatric disorder
• Have been clinically-diagnosed with diabetes, cardiovascular disease, or any otherunstable or serious medical condition.
• Current, or use within past month, of psychoactive (other than stable treatment withantidepressant or antianxiety), hypnotic, stimulant or analgesic medication (exceptoccasional non-narcotic analgesics)
• Shift work or other types of self-imposed irregular sleep schedules
• Habitual smoking (6 or more cigarettes per week)
• Habitual alcohol consumption (more than 2 alcoholic drinks per day)
• Breastfeeding or pregnancy