Heart rate was higher and heart rate variability lower (higher sympathovagal balance) during sleep in the room light versus the dim light condition. In the room light condition, participants spent proportionately more time in stage N2 and less in slow wave and rapid eye movement sleep. Melatonin levels were similar in both conditions. Measures of insulin resistance (morning homeostatic model assessment of insulin resistance, 30-min insulin area under the curve from a 2-h oral glucose tolerance test) were higher in the room light versus dim light condition. The dim light condition ( n = 10) included two consecutive nights of sleep in dim light. The room light condition ( n = 10) included one night of sleep in dim light (<3 lx) followed by one night of sleep with overhead room lighting (100 lx). A total of 20 young adults participated in this parallel-group study design. This study tested the hypothesis that acute exposure to light during nighttime sleep adversely affects next-morning glucose homeostasis and whether this effect occurs via reduced sleep quality, melatonin suppression, or sympathetic nervous system (SNS) activation during sleep.

Download endnote northwesern memorial