Room lights may affect sleep, hurt health

BOSTON, Jan. 13 (UPI) -- Bedtime electrical lighting may affect sleep quality and health -- including blood pressure and glucose levels -- a U.S. researcher cautions.

Lead author Joshua Gooley of Brigham and Women's Hospital and Harvard Medical School in Boston says indoor lighting may suppress melatonin -- a physiology-regulating hormone made at night in the brain's pineal gland.

The study, published in the Journal of Clinical Endocrinology & Metabolism, found exposure to room light vs. dim light in the hours before bedtime shortened melatonin duration by about 90 minutes. Room light during sleep hours suppressed melatonin by more than 50 percent.

"On a daily basis, millions of people choose to keep the lights on prior to bedtime and during the usual hours of sleep," Gooley says in a statement. "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."

Gooley and colleagues monitored blood plasma melatonin in 116 healthy volunteers ages 18-30 exposed to room light or dim light.