For Better Sleep, Don't Be Afraid Of The Dark

For a better night's sleep, maybe you don't need to count sheep or buy an expensive mattress. Maybe you just need to spend some time in the dark.

Researchers in Boston say exposure to electric light between dusk and bedtime strongly suppresses melatonin levels and may impact physiologic processes regulated by melatonin signaling, such as sleepiness, thermoregulation, blood pressure and glucose homeostasis.

Melatonin is a hormone produced at night by the pineal gland in the brain. It's useful when your body produces more of it.

Health benefits

In addition to its role in regulating the sleep-wake cycle, melatonin has been shown to lower blood pressure and body temperature and has also been explored as a treatment option for insomnia, hypertension and cancer.

In modern society, people routinely switch on the lights as soon as it gets dark out. As a result they are exposed to electrical lighting during evening hours as they continue to work or take part in recreational and social activities. The study sought to understand whether exposure to room light in the late evening may inhibit melatonin production and, as a result, make it harder to get a good night's sleep.

"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."

In this study, researchers evaluated 116 healthy volunteers who were between the ages of  18 and 30, and who were exposed to room light or dim light in the eight hours preceding bedtime for five consecutive days. An intravenous catheter was inserted into the forearms of study participants for continuous collection of blood plasma every 30-60 minutes for melatonin measurements.

Significant reduction

Results showed exposure to room light before bedtime shortened melatonin duration by about 90 minutes when compared to dim light exposure. Furthermore, exposure to room light during the usual hours of sleep suppressed melatonin by greater than 50 percent. The researchers say there's more at stake in just getting more shut-eye. More efficient melatonin production can have beneficial health consequences.

"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," said Gooley. "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."