Artificial light interrupts circadian ‘body clock’ cycle
Dear Doctors: We live in Northern California, and every time we have high winds, the electric company shuts off power because of the fire danger. We use candles and lanterns to light the house, and my husband thinks that he sleeps better on those nights. Do you think there’s a connection?
Dear Reader: Like most creatures, we’re keyed to the daily cycle of light and dark.
Research shows it plays out at the cellular and even molecular level as well.
This circadian cycle, often referred to as the body clock, guides metabolic and biological processes.
A number of these — including the regulation of body temperature, hormone secretion and alertness — play key roles in preparing the body to switch from wakefulness to sleep.
Studies have shown exposure to even small amounts of artificial light can delay the body’s sleep prep.
This means that the very first campfire humans lit to push back the night disrupted the sensitive mechanisms of the circadian cycle. As firelight gave way to candlelight, then to gas light and electric light, that disturbance grew more pronounced.
That’s because spending time in bright light slows production of melatonin, the hormone whose nighttime spike helps make us sleepy. The advent of blue light in all of the screens we use also wreaks havoc on sleep quantity and quality.
In a small study at the University of Colorado at Boulder, eight people camped in a wilderness area free of artificial light. They left all portable light sources behind and lived solely by natural daylight.
Lab tests showed that, after only a week, their daily melatonin rhythms and sleep schedules were syncing to the ebb and flow of light.
The takeaway? Due to reduced exposure to sunlight in our largely indoor lives and the near-constant presence of electric lights, human circadian physiology has been altered.
Another study found a wide range in tolerance to artificial light. For some, the dim glow of just a few candles caused the same drop and delay in melatonin production that others experienced only in the presence of sustained bright light.
So, yes, it’s entirely possible your husband’s sleep improves when his days and evenings are free from screens and electric lights.
This is important because insufficient and poor sleep are linked to serious health conditions including high blood pressure, depression, obesity and heart disease.
Spending more time in daylight and dimming the lights — and screens — after dark can add up to better sleep.
Eve Glazier, M.D., MBA, is an internist and associate professor of medicine at UCLA Health. Elizabeth Ko, M.D., is an internist and assistant professor of medicine at UCLA Health.