WASHINGTON (Dispatches) -- In a new study , researchers have found that being exposed to even a little light during nighttime sleep harms your cardiovascular function and increases your insulin resistance the following morning .
Previous studies indicated that that light exposure during daytime increases heart rate via activation of the sympathetic nervous system, which kicks your heart into high gear and heightens alertness to meet the challenges of the day.
The researchers tested the effect of sleeping with 100 lux (moderate light) compared to 3 lux (dim light) in participants over a single night. They found that moderate light exposure caused the body to go into a higher alert state. In this state, the heart rate increases as well as the force with which the heart contracts and the rate of how fast the blood is conducted to your blood vessels for oxygenated blood flow.
Exposure to artificial light at night during sleep is common, either from indoor light emitting devices or from sources outside the home, particularly in large urban areas. A significant proportion of individuals (up to 40%) sleep with a bedside lamp on or with a light on in the bedroom and/or keep the television on.