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Light exposure before bed suppressed melatonin levels
Gooley JJ. J Clin Endocrinol Metab. 2011;doi:10.1210/jc.2010-2098.
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Room light exposure before bedtime strongly suppressed melatonin levels, and may impact physiologic processes regulated by melatonin signaling, such as sleepiness, blood pressure, glucose homeostasis and thermoregulation, researchers have found.
The researchers evaluated 116 healthy participants, aged 18 to 30 years, who were enrolled in one of two studies. The volunteers were exposed to either room light (<200 lux) or dim light (<3 lux) for 8 hours before bedtime for 5 consecutive days. Blood plasma was collected via IV catheter continuously every 30 to 60 minutes during sleep to measure the melatonin levels.
Participants who were exposed to the room light before bedtime demonstrated a shortened melatonin duration by about 90 minutes compared with the dim light. In addition, participants who were exposed to room light during usual sleep hours showed that melatonin was suppressed by more than 50%.
“On a daily basis, millions of people choose to keep the lights on prior to bedtime and during the usual hours of sleep.
“Given that chronic light suppression of melatonin has been hypothesized to increase relative risk for some types of cancer, and that melatonin receptor genes have been linked to type 2 diabetes, our findings could have important health implications for shift workers who are exposed to indoor light at night over the course of many years,” Joshua Gooley, PhD, of Brigham and Women’s Hospital and Harvard Medical School, said in a press release.
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