Cardiometabolic Outcomes With Light Exposure During Sleep

Inclusion Criteria: * healthy adults * ages 18-40 years * habitual sleep duration of 6.5-8.5 hours * habitual sleep onset of 9:00 pm-1:00 am Exclusion Criteria: * any sleep disorder as assessed by history and screening questionnaires for obstructive sleep apnea (Berlin) and excessive daytime sleepiness (ESS \>12), and by PSG to exclude sleep apnea (apnea hypopnea index ≥ 15), periodic leg movements (movement arousal index ≥ 15), or REM sleep behavior disorder; * history of a cognitive or neurological disorder; * history of a major psychiatric disorder, including but not limited to mood/anxiety, eating, and alcohol/substance abuse disorders; * depressed mood (Beck Depression Inventory II score ≥ 20); * diabetes or other endocrine disorders; * any gastrointestinal disease requiring dietary adjustment; * blindness or significant vision loss; * any unstable or serious medical conditions; * current or recent (within the past month) of psychoactive, hypnotic, stimulant or analgesic medications; * shift work or other types of self-imposed irregular sleep schedules; * obesity (body mass index \> 30 kg/m2); * history of habitual smoking (6 or more cigarettes per week) or drinking (7 or more alcoholic beverages per week) or caffeine consumption greater than 300 mg per day; * current use of light therapy; * use of any other legal or illicit substance that may affect sleep and/or appetite; * allergy to heparin. * Due to the metabolic stress associated with pregnancy and breastfeeding, patients who were pregnant or breastfeeding were also excluded.