Exposure to room light before bedtime may impact sleep quality, BP

WASHINGTON - Exposure to electrical 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, according to a new study.

Melatonin is a hormone produced at night by the pineal gland in the brain. 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.

This study sought to understand whether exposure to room light in the late evening might inhibit melatonin production.

The researchers evaluated 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.

An intravenous catheter was inserted into the forearms of study participants for continuous collection of blood plasma every 30-60 minutes for melatonin measurements.

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 study appeared in the March 2011 issue of JCEM. (ANI)