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All living things have what’s known as a circadian rhythm – an approximate 24-hour cycle in physiological processes, including sleep. Your circadian rhythm is controlled by your internal body clock and can be affected by external factors such as light and temperature. A study conducted by researchers at Brigham and Women's Hospital in Boston sheds new light on the effects of night-time light exposure on your internal body clock.

Numerous studies have suggested that light influences levels of melatonin, a hormone produced in the brain at night, and resets the body’s internal clock, and that light exposure before bed suppresses melatonin production and reduces sleep quality. For this inpatient study, participants were exposed to either continuous or intermittent nighttime bright light for 9 or 10 days, while researchers looked the relationship between melatonin suppression and circadian rhythm resetting.

Intermittent light exposure was associated with substantial circadian rhythm shifts but significantly less melatonin suppression. Results of this study suggest circadian phase resetting and melatonin suppression are independent responses to exposure to light at night.