The Endocrine Society Indoor lighting in the evening hours has a suppressive effect on the hormone melatonin, or at least the following article suggests so. A groundbreaking study suggests that electrical light between dusk and bedtime has a strong impact on sleep quality, blood pressure and threat for diabetes. It is known that melatonin levels are capable of affecting physiologic processes that are controlled by melatonin signaling like sleepiness, thermoregulation, blood pressure and glucose homeostasis.

The study was conducted on 116 healthy volunteers aged 18-30 years who were exposed to room light or dim light in the eight hours preceding bedtime for five consecutive days. Authors inserted an intravenous catheter into the forearms of volunteers for continuous blood plasma collection every 30-60 minutes. Evaluating the accumulated blood plasma enabled scientists to make melatonin measurements. It was concluded that exposure to room light before bedtime lessens melatonin duration by approximately 90 minutes as compared to dim light exposure. When exposed to room light during the usual hours of sleep, melatonin is seemingly curbed by more than 50 percent.

Joshua Gooley, PhD, of Brigham and Women’s Hospital and Harvard Medical School in Boston, Mass. and lead author of the study, added, “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. Further research is still needed to both substantiate melatonin suppression as a significant risk factor for breast cancer and determine the mechanisms by which melatonin regulates glucose metabolism.”

The hormone melatonin is probably produced at night by the pineal gland in the brain and governs over the sleep-wake cycle. Melatonin also appears to lower blood pressure and body temperature. It was mentioned that majority of the people today are supposedly exposed to electrical lighting during evening hours that inhibits melatonin production.

The study will be published on the March 2011 in the Journal of Clinical Endocrinology and Metabolism (JCEM).