Lights At Night Increase Risks For Disease
Melatonin is a hormone that has many functions. Produced at night by the pineal gland, it regulates the sleep-wake cycle, body temperature, blood pressure, and glucose tolerance; lack of melatonin can create serious medical problems.
A study conducted by Brigham and Women's Hospital and Harvard Medical School looked at the effects of electric lighting between dusk and bedtime on the suppression of melatonin. Subjects were 116 healthy volunteers, aged 18-30 years, who were exposed to dim lighting or to room lighting for 8 hours preceding bed time on 5 consecutive days. Periodic blood draws measured melatonin production for each subject during the 8 hours.
The results showed that those exposed to room lighting before bedtime had shortened melatonin production by 90 minutes compared to those who were in dim light. Additionally, when exposed to room light during normal sleep hours, the sleep suppressed melatonin was reduced by 50 percent.
"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 Joshua Gooley, PhD, lead author of the study.
"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."
Still, you'd be wiser to use dim lighting in the evening. You'll sleep better and save on electricity!