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Lights Out Dusk to Bedtime Lowers Chances of Diabetes, Insomnia

Posted: Sunday, January 23, 2011

Turning down the lights from dusk to bedtime could induce sleep, lower blood pressure, curbing diabetes risk.

Scientists say electrical lights can suppress melatonin, an important hormone for sleep, glucose and blood pressure regulation that is produced in the pineal area of the brain.

"On a daily basis, millions of people choose to keep the lights on prior to bedtime and during the usual hours of sleep," said Joshua Gooley, PhD, of Brigham and Women's Hospital and Harvard Medical School in Boston, Mass. and lead author of the study. "Our study shows that this exposure to indoor light has a strong suppressive effect on the hormone melatonin. This could, in turn, have effects on sleep quality and the body's ability to regulate body temperature, blood pressure and glucose levels."

Turning out the lights at bedtime could also be important for reducing the chances of cancer say the researchers. For the study, scientists enlisted 116 healthy volunteers aged 18-30 years, exposing them to room light or dim light in the eight hours preceding bedtime, five days in a row.

The researchers measured melatonin levels in the blood every 30 to 60 minutes by way of an intravenous catheter inserted into the arms of the study participants, finding that lights in the room reduced melatonin levels an average of 90 minutes. 

Lights left on in the room during sleep suppressed melatonin levels by 50 percent. Dr. Gooley explains the findings may have important implications for shift workers who may be exposed to indoor light during night time hours for years.

The new findings suggest turning down indoor lighting at night, and keeping the room dark during sleep could reduce insomnia, keep blood pressure in check and lower the chances of developing diabetes. Melatonin has been studied for its role in treating cancer, poor sleep and hypertension, making the findings of interest for future research.  

Source:, J. Clin. Endocrinol. Metab.doi:doi:10.1210/jc.2010-2098

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