NEWSLETTER #183: The Perils of Blue Light at Night 📱
Happy weekend humanOS friends! This week, we took a look at some research examining the impact of short-wavelength light exposure at night. Seems like an appropriate topic, since Daylight Saving Time is about to conclude here in the US, right?
This is a dilemma that the majority of us can relate to. People spend countless hours interacting with digital devices, and that has only increased over the past decade or so. A Pew Research Center survey from this year found that 31% of American adults report that they are online “almost constantly” - up from 21% in 2015. This is sort of inevitable, due to the nature of modern work and our social lives, but it comes with a price: the screens of these devices - including computers, tablets, and smartphones - all emit significant amounts of short-wavelength light.
This type of light is good during the day, because it tends to boost alertness, but abundant research shows that it disrupts sleep and circadian alignment in the evening. For instance, when participants in a sleep lab were given unrestricted access to an iPad for five days, they went to bed later, their melatonin levels were suppressed by more than 50%, and the timing of their circadian rhythm onset was 48 minutes later on average, compared to when they were limited to only printed reading materials.
Fortunately, there are some things that you can do about it, even if quitting your smartphone is a total non-starter. Some research suggests that using glasses with special lenses that filter out high-energy short-wavelength light can help mitigate the deleterious effects of such light on sleep and circadian rhythms.
This Week's Research Highlights
🧠 People who were exposed to dim light while sleeping experience altered brain function.
Researchers in South Korea recruited 20 healthy male subjects and had them spend two nights in a sleep lab in darkness, followed by a third night under very dim light. After each night, the men were tested on their working memory, and the researchers conducted fMRI scans to assess brain activation during the cognitive testing. After a single night of sleeping under dim light (10 lux), the men showed decreased brain activation as well as poorer performance on the cognitive test, compared to when participants slept in complete darkness.
😴 Exposure to blue light before bedtime results in poorer sleep quality.
Researchers in Japan exposed 11 healthy young men to three conditions for one hour before bedtime: 1) incandescent light, 2) blue-light, or 3) blue light but with blue light-blocking glasses on. There was not a significant difference in total sleep time between the conditions, but exposure to blue light resulted in a significant decrease in the ratio of deep sleep (47 minutes, 18.4% of sleep), compared to both incandescent light (61 minutes, 26% of sleep) and to blue light while wearing blue-blocking glasses (69 minutes, 29.3% of sleep). Getting adequate deep sleep has been shown to be particularly important for memory and cognition - if you wanna learn more about how to achieve greater amounts of deep sleep, check out our interview with Kristine Wilckens.
👓 Glasses designed to block short-wavelength light may protect against many of the sleep-disrupting effects of blue light.
So, we just saw in the preceding study that blue light exposure seems to impair sleep quality, but subjects who wore blue light filtering lenses while exposed to the light were shielded from this effect. To further explore the impact of blue-blockers on multiple aspects of sleep, researchers in Houston had participants wear blue-blocking glasses for about four hours each night, while continuing with their usual nighttime routine (including the use of mobile phones, tablets, and other light-emitting devices). The subjects also wore activity monitors to objectively measure movement, light exposure, and sleep, and saliva samples were collected to measure melatonin. After two weeks, they showed a 58% increase in their nighttime melatonin levels. They also went to sleep 27 minutes earlier, on average, and got 24 minutes more sleep per night.
Random Trivia & Weird News
🤔 Recent surveys of Americans and Britons found that Americans are consistently more confident in their ability to defeat various species of animals in unarmed combat, compared to their trans-Atlantic counterparts. Just as one illustration of this boundless (and somewhat alarming) optimism, 8% of US respondents said they believed they could successfully take on an elephant or a lion.
Podcasts We Loved This Week
• David Nutt: Psychedelics and recreational drugs. Via Peter Attia.
• Meghan O’Rourke: America’s chronic disease epidemic and what it reveals about our healthcare, culture, and society. Via The Ezra Klein Show.
Products We Are Enjoying
Blue Light Blocking Computer Glasses
These glasses are super inexpensive, come in lots of colors and styles, and are pretty much perfect if you have a job that involves looking at a computer screen in the wee hours (or if you just like to play on the phone/tablet at night). But what makes them really useful is that they filter UV and some blue light, but they look mostly clear, without any weird orange tint. Plus they don’t look weird, like some blue-blockers, so you’re more likely to wear them. 🤓
humanOS Catalog Feature of the Week
Thanks for reading, and I will see y'all next week!