Too Much Light: Ruining Not Just Your Sleep But Your Health Too

Falling asleep with the TV on or a dim night-light in your room may seem soothing. But these seemingly innocent light sources could also form barriers between you and healthy sleep.

Falling asleep with the TV on may ward off the bogeyman, but research suggests that, over time, too much light at night could interfere with healthy sleep, possibly increasing your risk of sleep disorders and other health problems. According to emerging research, sleep disorders and nighttime lighting may be making us fatter, more depressed, and more likely to develop cancer.

You’re not alone if you find yourself falling asleep to the glow of the TV or a computer screen. But, says insomnia researcher Colleen Carney, PhD, associate professor of psychology at Ryerson University in Toronto, her patients’ reluctance to turn off these light sources in order to get a better night’s sleep gave her an idea that research later confirmed: The need for the TV, a spouse, or a light source to feel comfortable falling asleep may be rooted in a fear of the dark.

Carney and her team looked at the nighttime and daytime startle responses of close to 90 undergraduates. Those who said they had trouble sleeping were also more likely to startle in response to loud noises in the dark. Since the researchers excluded people who had post-traumatic stress disorder (PTSD), a condition in which individuals are already hyperalert, they concluded that the results suggest that people who say they sleep poorly might have a low-grade fear of the dark. And, Carney says, the best way to get over that fear is to gradually spend more time in the dark until falling asleep in the dark gets easier.

Light’s Effect on Sleep/Wake Cycles

Our body’s basic rhythms, including our sleep/wake cycles, are tied to light exposure, argues sleep researcher Christopher Drake, PhD, of the Henry Ford Hospital in Detroit. Drake has published research in Chronobiology International that explores changes in these rhythms in shift workers who are faced with the challenge of sleeping during the brightness of day and working in the poorly lit night.

Ordinarily your body produces the soporific (sleep-inducing) hormone melatonin as a preparation for sleep. But, says Drake, “light actually suppresses melatonin.” Melatonin suppression caused by light is at the heart of much of the research linking nighttime light to sleep disorders and poor health. The effect of even a brief amount of light is long-lasting. Bright light late in the evening — around midnight — can push your sleep/wake cycle back by half an hour or so, making you sleepy later in the evening the following night. On the other hand, bright light early in the morning, when you first wake up, advances your cycle, bringing on sleepiness earlier. For people whose light exposure and sleep habits are chaotic, the end result is a disordered sleep/wake cycle and related poor health outcomes.

The connection between nighttime lighting, sleep disorders, and health risks is so strong that the American Medical Association recently issued a statement emphasizing the risk and calling for the development of nighttime lighting technologies that would not interfere with the body’s basic rhythms. The World Health Organization already recognizes shift work as a risk factor for developing breast or prostate cancer, specifically because of the way in which light at night negatively affects all the body’s cycles, including sleep and wake cycles.

If overcoming your fear of the dark isn’t reason enough to turn out the lights, consider the impact of sleep disorders and poor sleep on your health. You’re risking:

Depression. Sleep disorders are strongly linked with the risk for depression and the experience of depression. Research published in the journal Molecular Psychiatry shows that even dim lighting at night — the equivalent of a night-light — can increase physiological changes that lead to depression in rodents. “In hamsters, dim light at night provoked depression-like behaviors and changes in the brain. This could be occurring through disrupted circadian rhythms or suppression of melatonin,” says researcher Tracy Bedrosian, a PhD candidate in the department of neuroscience at The Ohio State University in Columbus. The good news is that the symptoms reversed themselves when normal lighting conditions were restored.

Cancer. Light at night (known to researchers as LAN) is a significant risk factor for developing breast cancer, according to researchers who reviewed data from 1,679 women and published their findings in Chronobiology International.

Reproductive health. Publishing in Epidemiology, researchers report that rotating shift work, which leads to increased exposure to light at night, appeared to disrupt the menstrual cycles of female workers. The research involved 71,077 women who participated in the Nurses’ Health Study II. About one in five participants worked a nontraditional shift for at least a month in the two years before the study. The more time spent on shift work, the more irregular the cycles became. Researchers theorize that the disordered exposure to light and chaotic wake/sleep cycles could interfere with fertility over time.

Obesity. According to research published in the Proceedings of the National Academy of Sciences, even dim light at night may be reorganizing other physical rhythms, such as eating schedules. Researchers exposed mice to dim light at night over eight weeks and found that the mice gained more weight than those not experiencing nighttime lighting. And, say the researchers, at least in mice, this gain appeared to be due to disordered eating. In contrast, mice exposed to light at night, but with food limited to scheduled eating times, did not gain excess weight.

How to Face the Dark

Whether you leave a light on purposely or accidentally because you often drift off to sleep while watching TV, here are steps you can take to limit the way that light may be affecting your sleep:

Seek light when you wake up. Bright light — ideally sunlight — when you wake up will help your body set its internal clock, especially if you keep a consistent wake time.

Turn off all screens. TV, computer, smartphone, tablet, reading device — turn them all off when you go to bed. Better yet, turn them off at least an hour before. Even their seemingly innocent glow interferes with sleep, possibly because they shine directly into your eyes.

Face your fear of the dark. If you suspect that you have a darkness phobia, you can overcome it, often with the help of just about any self-help book on conquering phobia through exposure, says Carney. If you’re still feeling anxious at the thought of falling asleep without the TV on or a comforting light, seek help from a therapist trained in cognitive behavioral therapy, a therapeutic approach that has been shown to work well for both sleep disorders and phobias.

Limit light while sleeping. In addition to turning off all the lights under your control, you might need to put up light-blocking shades or curtains to keep ambient light, such as your neighbor’s porch light, out of your room. You might even try wearing a sleep mask over your eyes.

Pick red or orange night light. Bedrosian points out that the depressive effects of night-lights in hamsters would occur in humans with lights about four times brighter, so outlet night-lights should be fine for you. However, if you’re still concerned, red/orange light does not affect the circadian system in the same way as white/blue light, so using colored light might be an effective option, she says. The American Medical Association recommends dim red night lighting.

Don’t turn on lights at night. If you have to get up from sleep to use the bathroom or for other reasons, do not turn on bright lights. Instead, use a flashlight or plan ahead and place red/orange night-lights in appropriate places in your home.

Learn shift work sleep strategies. About one in five people works a schedule other than the traditional 9 to 5, according to the Bureau of Labor Statistics. People who work at night and have to sleep during the day face additional light-control challenges. Their best bet, says Drake, is to seek out brightly lit environments in the wee hours (midnight until about 3 a.m.) and then block out bright light (such as the rising sun) on their way home to sleep. Wear sunglasses or goggles to achieve this, and create a totally dark, quiet sleep environment at home.

Our modern world is so well-lit that it might seem hard to dim the lights in preparation for sleep and then seek near-total darkness for sleep. But according to emerging research, your best bet for healthy sleep is to do just that.

By Madeline R. Vann