Light exposure at night may not only disrupt sleep but also adversely impact metabolic function, according to a study.
"Our preliminary findings show that a single night of light exposure during sleep acutely impacts measures of insulin resistance," said Ivy Cheung Mason, a postdoctoral fellow at Northwestern University Feinberg School of Medicine in the US.
"Light exposure overnight during sleep has been shown to disrupt sleep, but these data indicate that it may also have the potential to influence metabolism," said Mason.
Twenty healthy adults aged 18 to 40 were randomised into Dark-Dark (DD) or Dark-Light (DL) groups and run in parallel for a three day and two night stay.
Participants had eight hours of sleep opportunity each night starting at habitual bedtime determined from one week of actigraphy with sleep diary.
The DL group slept in the darkness less than 3 lux light on Night 1 and slept in overhead room light of 100 lux on Night 2, while the DD group slept in the dark less than 3 lux of light on both Nights 1 and 2.
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Overnight polysomnography and hourly blood sampling for melatonin were collected on both nights.
Oral glucose tolerance tests were performed on both mornings following sleep in the dark or 100 lux of light.
Changes from Day/Night 1 to Day/Night 2 were examined between DD and DL groups.
Homeostatic model assessment of insulin resistance change values were significantly higher in the morning following sleep in the light (DL group) compared to sleep in the dark (DD group). This effect was primarily due to increased insulin levels for DL compared to DD group.
Results show that a single night of light exposure during sleep acutely impacts measures of insulin resistance.
Insulin resistance is the diminished ability of cells to respond to insulin action transporting glucose out of the bloodstream and precedes the development of type 2 diabetes.
"These results are important given the increasingly widespread use of artificial light exposure, particularly at night," said Mason.
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