Light is one of the most critical factors that helps to regulate your sleep and wake cycles. But it’s not just sunlight isn’t the only kind of light that affects sleep — a recent study shows how the lighting in your home, and even the choice of lightbulbs you use can also interfere with your body’s ability to wind down for the night.
How exposure to light affects your circadian rhythms
Your circadian rhythms, or internal body clock, help control your natural sleep-wake cycle. These rhythms have been shown to be incredibly sensitive to any kind of light, whether that be natural (solar) or artificial lighting. When and how you expose yourself to light has a big impact on your circadian rhythm and the biological clocks that control many bodily functions, like digestion, hormone regulation and body temperature.
Before the advent of industrialisation, most humans used to wake and sleep in sync with the rising and setting sun, but in modern society, this natural rhythm has been thrown off by artificial lighting in our homes. Humans are also drawn to light because it can boost mood and energy, and artificial lighting in our homes has also allowed us to work, read or entertain ourselves with screens in the evenings.
“It’s something that probably served us well in our evolutionary past when getting as much light as we could was good because it was perfectly timed and it was good information for the [internal] clock,” says Sean Cain, Ph.D., an associate professor of psychology at Monash University in Melbourne, Victoria, Australia. “But now that we’ve got light whenever we want, these drives to consume light are negative for us.”
Light blocks the production of melatonin, which helps you fall asleep, so exposure to light before bed can impact your ability to fall asleep as well as your overall sleep quality, Cain says. In fact, research shows that spending time in a fully lit room before trying to go to sleep can cause your body to delay and shorten melatonin production compared to spending time in a dimly lit room before trying to sleep.
“[Some] people are wondering maybe why they have trouble getting to sleep, but they never think it’s the light,” Cain says. “We’re not used to thinking that light is important.”
The type of lighting in your home matters
Exposing yourself to any kind of artificial light before bed can disrupt your sleep, but some types of light suppress melatonin more powerfully than others. Blue wavelengths, which are present in sunlight, electronic screens and energy-efficient LED lighting, suppresses melatonin for a longer period of time than other types of light, like green or red wavelengths.
A recent study, which Cain co-authored, examined the effects of different types of home lighting on melatonin production and found that homes with energy-efficient lights had almost double the melanopic illuminance, or melatonin suppressing effects, than homes with incandescent lighting. Out of 56 participants examined in the study, nearly half had light bright enough in their homes to suppress melatonin by 50%.
“This switchover [to LED lights] that is beneficial for energy consumption is probably having a negative impact on our health,” Cain says. “I don’t think the general public knows that much about the potential negative effects of light.”
Researchers note, however, that sensitivity to light varies among people and not everyone’s circadian system responds in the same way to the same home light environment. Still, greater exposure to light in the evening is associated with increased wakefulness at bedtime and can have an effect on your quality of sleep.
How to adjust the lighting in your home to improve your sleep
The type of lighting and time of day you’re exposed to light can throw off your circadian rhythm and make it harder to fall asleep. Fortunately, there are ways to control your environment and improve your sleep hygiene. Here are some tips:
Switch to dimmer, warmer lights in the evening. Cain recommends doing this at least three hours before bedtime. Energy-efficient LED bulbs are great for daytime use, but they suppress melatonin production more powerfully than incandescent light.
Turn off screens at least half an hour before bed. Light from laptops, cell phones or tablets can inhibit your ability to wind down for the night.
Expose yourself to as much natural light during the day as possible. This helps reinforce your body’s natural sleep-wake cycle.
If you use night lights or lamps in the evening, switch them over to amber bulbs for warmer light.