Electric lighting interferes with the body's circadian clock, researchers say

It's hard to imagine a life without electric lighting: we'd be in the dark, and probably inactive and unproductive, for about half the day. But would we be healthier without it?

A University of Colorado Boulder research team set out to quantify the effects of electric lighting, which became widely available in the 1930s. They monitored eight participants - six men and two women with an average age of 30 - for one week as they went about their normal lives, and a second week as they camped in Colorado's Eagles Nest Wilderness.

The participants wore wrist monitors that recorded the intensity of light they were exposed to, the timing of that light and their activity. The timing of their circadian clocks - the body's internal time-keeper that directs the sleep-wake cycle - was also recorded by measuring melatonin levels, a hormone that is released during the biological nighttime and decreases during daytime.

After the camping trip, during which they experienced only sunlight and a campfire, all the participants' sleep-wake cycles became in sync with sunset and sunrise, in spite of their previous propensity to be night owls or early birds. On average, their biological nighttimes started about two hours earlier than when they were exposed to electrical lights.

The study, published earlier this month in the journal , shows how artificial lighting can affect the body's internal clock - a disruption which researchers are increasingly showing can have grave consequences for our health.

The role the circadian clock plays in disease and genetics is slowly being unravelled and understood. Some of the latest findings show that women who do shift-work have an increased risk of menstrual disruption and subfertility; that the body clock has an intrinsic power to help fight intestinal bacterial infections; and that severe depression could be linked with altered genes that control the circadian clock.