What it is:
Clock genes operate on a 24-hour cycle and are found in virtually all cells of the body. A central clock in the brain keeps all the body’s cells synchronized by using ambient light levels in the environment to send either “daytime” or “nighttime” signals downstream to different tissues and organs.
Our “clocks” can be modified, to some extent, by strategic use of timing cues, such as light exposure or meal and exercise timing. Still, it is theorized that somewhere between 20 and 50% of our “chronotype” (unique signature for how much of a “morning” or “evening” person we are) is determined by our genes. If we try to fight this intrinsic timing mechanism significantly, we can experience adverse health consequences. At the mild end of the spectrum, this might include fatigue, trouble concentrating, and mood symptoms. However, under chronic “circadian misalignment”, this might consist of more severe diseases.
Working in synchrony with our internal body clocks is the best way to get the most out of our days and feel our best. This process begins by identifying our most optimal timeframe for wake and sleep. This varies from person to person and isn’t always compatible with external demands from life and work. But it becomes evident on vacation or when we have the option of work flexibility. When there are no external pressures to stay awake later than the point at which we would rather go to bed or wake up with an alarm earlier than when we are ready, we can begin to notice our natural rhythms.
We can dive one step further than this and start to get the most out of our time awake by paying attention to how we feel across the day. For some people, the morning is the best time of day for getting stuck into and making progress on “deep work.” For others, this time comes in the afternoon. These peak performance windows are often dictated by how much time has passed since we woke up. The daytime dip in alertness and mood will arrive earlier for individuals who naturally wake up earlier.
The standard 9-to-5 workday, where one is expected to work with equal motivation and focus throughout this entire period, is virtually impossible from a circadian rhythm perspective. In fact, cultures that support a leisurely lunch break or post-lunch siesta are much more aligned with our internal drive for activity in the morning, an extended mid-day break, and activity once again after the post-lunch dip. Trying to muster up the strength to persevere through natural circadian dips can often result in frustration and a drive towards dependence on caffeine to remain alert.
Instead of trying to make ourselves fit into an arbitrary work window that isn’t necessarily compatible with what our bodies desire, we can optimize conditions when we are “on” to get the most out of that time frame. This allows us to get more done in less time, leaving us more availability for rest, hobbies, and time with family and friends. How we choose to light our environment (or avoid light if we are trying to promote sleep) is extremely important for setting ourselves up for success. Below are some strategic lighting considerations to implement at home, in the office, and while traveling to get the best out of your days.
The purported claims:
Timing and quality of light matters for cognition and mood.
The angle at which the light hits our eyes should be modified based on time of day and need.
Smart lighting can be used at home and while traveling to improve circadian health.
What the science says:
Circadian Timing and Amplitude
Our exposure to light is important for influencing two aspects of our circadian rhythms: timing and amplitude. Circadian timing is where we are in the biological day. Because of this, there has been a movement in the public health and wellness space to focus on the importance of morning sunlight exposure. Exposing ourselves to light upon waking sends a strong signal to our brains (via specialized light-sensing cells in the retina) that it’s the morning. The exposure to daylight (even if there is cloud coverage) allows plenty of blue light to enter the eyes and activate wakefulness and alertness pathways in the brain. Unless we can follow our morning routine in brightly lit spaces with large windows and high-quality daylight-mimicking bulbs, it is virtually impossible to mimic the quality of light that comes from stepping outside.
Just as morning light exposure tells the brain it is morning, so does the transition to dim light conditions at night, which starts a cascade of physiological processes to promote sleep. Working in opposition to the blue-light-stimulating effects of daylight, the absence of blue light allows our brain to trigger the synthesis and release of the hormone melatonin, beginning about 60-90 minutes before we naturally start to feel sleepy.
Working in synchrony with circadian timing is circadian amplitude. That is: how large a difference there is between the daylight we are exposed to during the day, and the darkness we are exposed to at night. We are learning more and more that maximizing this difference is important for not only boosting mood and alertness when we want it, but promoting a stronger drive to sleep at night. Importantly, in a time of excessive exposure to artificial lights at night, sending a strong “daytime” signal via bright lighting during the day may protect against some light exposure at night. One of the worst things we can do for our circadian health is combine too much time indoors in dim light conditions during the day, with too much light exposure at night. Under these circumstances, the brain receives much weaker signals about where we are in the solar day, and we might notice symptoms such as daytime sleepiness, a depressed mood, and trouble concentrating, combined with insomnia at night.
Research at Stanford University has shown that brighter daytime light is associated with fewer awakenings during the night. Interestingly, maximizing daylight exposure between six and seven hours after waking up might be the best time to improve sleep quality that night. This suggests that a lunch break spent outside in the sun might actually promote better sleep health.
Dynamic Lighting
Some researchers have investigated how dynamic lighting, which changes in intensity and warmness/coolness throughout the day, can help workers strike a balance between maximizing alertness and mood without causing eye strain or headaches. Dynamic lighting works by automating a shift from bright and cool-toned lighting first thing in the morning to dimmer and warmer lighting by the time the lunch period arrives. Then, to counter the post-lunch dip in energy, this bright and cool to dimmer and warmer light progresses again until the end of the workday, with a final boost of light right before workers depart for the day and probably want their wits about them during the commute home. See an example below of how this dynamic lighting works.
The best way to implement dynamic lighting in your workplace or home is with programmable smart bulbs that can shift automatically across the day or with simple instructions depending on requirements. Rather than using standard dimmer switches, smart bulbs offer color-changing options as well. One can sync these bulbs with an app or home hub and double up as a great option for home lighting automation when you’re out of town.
The technology is changing rapidly, but as of the time of writing, Philips Hue and Nanoleaf bulbs are some of the more popular, premium offerings that can be connected to a home hub such as Apple HomeKit, Amazon Alexa, or Google Home. These bulbs allow users to create pre-set options for different times of day, as well as additional modes that might be useful for scenarios such as being away from the home or entertaining guests. Refer to the References and Additional Materials section at the end of this article for a couple of simple guides if you’re interested in getting started or expanding your use of smart lighting.
An additional consideration is the lighting fixtures themselves. The angle at which the lighting in your home or workplace hits your eyes is important, depending on the effect you would like it to have. Lighting above eye level (such as overhead fixtures) will generally promote alertness and is best for when we are hoping to remain focused, while lighting below eye level (such as table lamps) is encouraged when we are trying to wind down for the evening.
Some Considerations for Travel
When we are away from home, it can be challenging to follow our usual routines. We might not worry so much if we are on vacation, but when traveling for work, we usually want to feel our best and may also have the effects of jetlag or limited meal options working against us.
The more attention we pay to our lighting and the more benefits we reap from tailoring our workplace or home lighting to meet our unique needs to improve cognition or facilitate rest, the more we might become aware of how unfriendly to circadian rhythms lighting can be in many other places.
When having to work away from the office, prioritize bright, natural lighting from first thing in the morning until the end of the work day. If you can turn on overhead lights without causing eye strain, be sure to do so, as these will further promote alertness. An ideal option is to find a workstation next to a large window and work there if you can.
When the time comes to rest and relax in the evening, utilize dimmable lighting options and consider a color-changing travel light, such as the OLight OBulb Pro. This is a rechargeable, dimmable, color-changing light that can be controlled with your smartphone and is compact enough to easily take with you on overnight stays. In the event that you might not be able to create a dark room at night, be sure to travel with an eye mask to support healthier sleep.
Our take:
Strategic exposure to lighting and darkness is a powerful tool for improving our health, mood, and cognition. Morning light helped us move from a sleepy state into one of alertness. Bright natural light is the preferred option to optimize health, but dynamic indoor lighting might help maximize productivity while preventing eye strain and headaches for individuals who primarily work indoors without much natural lighting. Finally, exposure to dimmer, warmer lighting as we ease towards bedtime will again support our natural melatonin production and relaxation before sleep.
Introducing smart lighting into your home and office may surprise you by just how much you enjoy it. You might notice a boost in mood, workflow, and sleep quality. Opt for portable travel lights with color-changing and dimmable settings to avoid having to use harsh lighting at night when you are on the go.
Will this benefit me?
Biomedical researchers are now realizing that circadian rhythms are at the foundation of every process in the body. Just as in 2016, when the National Institutes of Health mandated that all studies must include both males and females (given the ways that sex hormones can influence different aspects of physiology and pharmacology), there is now a similar push for researchers to consider how time of day impacts experimental outcomes and how they can best control for time of day in their studies.
Humans, along with all other animals, have evolved with the rhythms of the solar day and night for millennia. While the industrial revolution and invention of electric lighting drastically changed the way that humans are able to live, work, and sleep, our brains still very much operate as they did in ancient times when our only sources of light were the sun by day, and campfires, lightning, and the moon by night. Combat the deleterious effects of too much time spent indoors during the day by optimizing your lighting for wakefulness and alertness, and protect yourself from excess light at night by leaning towards warmer, dimmer lighting as you ease to sleep.
Still curious to try it? If you do, here’s what to keep an eye on:
It can be easy to feel stressed when headline after headline tells us how sleep loss and circadian misalignment lead to disease. However, it’s important to remember that the path to health is often found by keeping things simple. The lighting options suggested here may be attractive to anyone looking to optimize their cognition, but even without all the fancy smart bulbs, circadian health can be achieved by spending plenty of time exposed to natural light during the day and keeping things dark at night. If you listen to your body carefully, chances are you already know the kinds of lifestyle behaviors that might help you feel your best. So trust yourself, and before throwing something else at your routine, ask whether you might stand to benefit by simply taking something away.
References and additional materials:
Genetics of chronotype - https://www.nature.com/articles/srep09214
Genetics of chronotype II - https://theconversation.com/morning-or-night-person-it-depends-on-many-more-genes-than-we-thought-110256#:~:text=Men%are%more%likely%than,what%these%genetic%factors%were
Bright light and circadian amplitude - https://www.pnas.org/doi/full/10.1073/pnas.2100094118
Light exposure and sleep fragmentation - https://www.frontiersin.org/journals/sleep/articles/10.3389/frsle.2023.1268379/full
Workplace lighting - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6264480/
Guide to smart lighting - https://www.theverge.com/23156554/smart-bulbs-switch-lighting-guide-how-to
Philips Hue vs Nanoleaf guide - https://www.cnn.com/cnn-underscored/electronics/philips-hue-vs-nanoleaf-essentials
Recommendations for lighting according to circadian biologists - https://pubmed.ncbi.nlm.nih.gov/35298459/
Huberman Lab “Using Light for Health” - https://www.hubermanlab.com/newsletter/using-light-for-health
O-light o-bulb - https://www.olightstore.com/obulb-pro-s-multi-color-light\
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