Morning and Evening Blue-Enriched Light Exposure Alters Metabolic Function in Normal Weight Adults
Schematic representation of the experimental protocol for morning (A) and evening (B) light exposure. Participants arrived in the early evening of Day 1 (not shown) and began dim light < 20 lux (light grey shading) on Day 2 during 16 hours of wake and < 3 lux (dark grey shading) during 8 hours of sleep. Fixed isocaloric meals were given 1, 5, and 11 hours after wake. On both Days 2 and 3, questionnaires (VASH and KSS) were collected hourly during wake and blood was drawn (black circles) at 30-minute intervals 0.5–4.5 hours after wake for morning light exposure participants (A) and 10.5–14.5 hours after wake for evening light exposure participants (B). Participants were exposed to 3 hours of blue-enriched light (hashed shading on Day 3) starting 0.5 hours after wake for morning light exposure participants (A) and starting 10.5 hours after wake for evening light exposure participants (B) compared to dim light (Day 2). Participants were discharged on Day 4 (not shown). Abbreviations: VASH–visual analogue scale for hunger, KSS–Karolinska Sleepiness Scale.