Wierd Discovery: How Leaving The Light On All Night Messes With Sleep

Sleeping with the light on could lead to worse Zzs, a small new study suggests.

Reuters first reported on the study, published in the journal Sleep Medicine, which showed that sleeping with the lights on is linked with waking up more often in the middle of the night and having more shallow sleep. Plus, it seems to affect brain oscillations that are linked with sleep depth.

Ten study participants with healthy sleep patterns underwent two sleep sessions where they were monitored using polysomnography. In one of the sessions, they slept with the lights on, and in the other, they slept with the lights off. Reuters reported that the light came from a fluorescent lamp just a few feet away from the participants.

The South Korean researchers found that when the participants slept with the lights on, they had more shallow, stage 1 sleep and less slow-wave sleep, as well as increases in arousal during sleep. There were also changes to brain oscillations, “especially those implicated in sleep depth and stability,” they wrote in the study.

However, Michael Gorman, a biopsychologist at the University of California, San Diego, who was not involved in the study, told Reuters that the light used in the study was “not like the light from your alarm clock.”

While this study showed the potential impact of lights during sleep, past research has also shown that lights before sleep can take a toll. A perspective article published in the journal Nature earlier this year, written by Harvard sleep medicine professor Charles A. Czeisler, M.D., Ph.D., detailed how artificial light stops sleep-promoting neurons and activates neurons linked with arousal. Czeisler highlighted the association between the rise of electric light and the rise of sleep deficiency.

According to the National Sleep Foundation, an optimal sleep environment is vital to getting a good night’s rest — and that includes keeping a dark bedroom before heading off to slumberland. The National Sleep Foundation provides the following recommendations for minimizing light pre-sleep:

At bedtime, think dark: a dark bedroom contributes to better sleep. Try light blocking curtains, shades or blinds. If you find yourself waking earlier than you’d like, try increasing your exposure to bright light in the evening. It may delay sleep onset but as little as one to two hours of evening bright light exposure may help you sleep longer in the morning. Also, make sure to avoid light if you wake up in the middle of the night to go to the bathroom. Minimize light by using a low illumination night light.