How to Align Your Circadian Rhythm for the Perfect Sleep Schedule

Circadian Rhythm

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Your ability to get good quality sleep hinges on whether your circadian system is properly aligned with your desired day/night cycle.

If your brain and body think it’s still time to be awake when you want to go to bed, guess what? You ain’t goin’ to bed. *sassy finger snapping*

What is Your Circadian Rhythm?

Human beings require daily exposure to bright light to help attune our internal clocks to the rhythm of the Earth.

graph showing the daily rhythms of cortisol, melatonin, growth hormone, potassium, and temperature
As you can see, there are many things in the human body that function on a 24 hour cycle.

We’re going to go over some strategies you can implement to make sure the right signals are being presented at the right time.

I’m not going to get into the nerdy nitty gritty circadian biology stuff here, there’s plenty of that out there already, this guide will focus on the practical application side of things.

Defining Your Sleep Schedule

Before we get into the daily strategies that will help align your circadian rhythm and get you sleeping like a freshly suckled baby, we need to go over some ground rules.

  • Schedule the time: As an adult, you should be getting around 7-9 hours of sleep every 24 hours. Make sure you are giving yourself time for this. You should be able to wake up naturally to a light alarm after 8 hours or so of sleep without the need of an audible alarm.
  • Step it back if you need to: If the thought of not using an alarm clock perturbs you, slowly step back your bedtime until you can comfortably risk sleeping in a bit in the morning. If you need to step it back by an hour, don’t try it all at once, do 10 minutes every 2-3 days.
  • Keep the same bedtime: Go to bed at the same time every day! You need to stay consistent if you want to sleep well within a confined work-life schedule, there’s just no way around this. Social jet-lag is fine and understandable if it’s not happening every weekend, and it isn’t negatively affecting your quality of life.
  • Pay attention to your drowsiness: Even if you think doing everything right, you may need more sleep. I you notice you’re consistently tired during the day (not just after lunch) you may just need to step that bedtime back, or have your dawn simulation turn on a little later. These things can take time to figure out.

Waking up in the Morning

Circadian alignment begins first thing in the morning, so this is where we’ll start.

Use Dawn Simulation for the Best Wake Up

Waking up naturally and as peacefully as possible sure does sound nice, doesn’t it?

We should be waking up with dawn, as the light and temperature slowly increase, our brains bring us out of sleep when they’re ready to.

So if we want to start our day’s off on the right foot, we want to simulate dawn.

The Science Behind Dawn Simulation

  • In this small trial, eight participants were separated into a control or dawn simulation group. The dawn simulation group experienced better perceived sleep quality, significantly higher alertness, improved cognitive performance, and better times in a self-paced cycling exercise. [R]
  • In this study, subjective sleepiness after waking was significantly lower in the DsL group. Better waking was attributed to a quicker decrease in skin temperature, signifying better distal to proximal skin temperature regulation. While the authors state that no significant cortisol secretions were found, the DsL group clearly has higher waking cortisol up to 30 minutes. [R]
  • The use of the artificial dawn resulted in a significant reduction of sleep inertia complaints. The dim light melatonin onset (DLMO) was the same in all groups. [R]
  • In this study, participants were sleep restricted for two nights in a row and put into one of three light experiments. Mood and well-being were significantly enhanced after exposure to morning dawn simulation light compared with the dim light and blue light groups. Salivary cortisol was also higher post wake-up in the dawn simulation group. [R]
  • Seventeen young men were woken up two hours before their normal wake time. In the group that had dawn simulation light (DSL) 30 minutes before being awoken, there was a significantly calmer heart rate gradient upon waking. [R]
  • In this study, the participants who were subjected to changing temperatures similar to the patterns seen in nature, i.e. a gradual decrease as bedtime approached, and a gradual increase as the wake-time approached, experienced better waking sensation and higher urine melatonin on waking. [R]
  • Gradual changes of light and temperature both in the morning are associated with high melatonin levels in the morning and lower drowsiness upon waking. [R]

How to Simulate Dawn Light

As you can see, simulating natural dawn, both with gradual light changes and temperature changes, can make a difference in our circadian biology.

Here are some things you can do:

  • Buy a wake-up light: Philips currently makes the best one, but it’s also the most expensive, there are also plenty of generic cheaper ones if you can’t afford that. I’ve also managed to locate an android app that mimics this somewhat by slowly increasing the brightness of a white screen, and that’s free.

  • Using your wake-up light: You want it to reach full brightness at your desired wake-up time. Setting it for a half hour is enough, although you can experiment with longer. Do not use the audible alarm functions. Being jolted out of your peaceful slumber at a specific time, whether you’re in light, deep, or REM sleep, is completely unnatural and nobody likes doing that anyway.

How to Simulate Dawn Temperature Rise

  • Heating the ambient air: Set your thermostat to slowly increase the temperature over a 2-hour period by at least 5 degrees. If you don’t have this capability, you can also schedule a room heater to do the same thing with an outlet timer, just make sure it’s in a safe place, and you have a smoke detector in the room! Safety first. A programmable radiant oil heater is also a good option.
  • Bedjet: The Bedjet is another option for slowly warming up your microclimate. This is my preferred method as it preserves the natural feel of your mattress, unlike pad-based cooling gadgets.

Get Bright Light Exposure ASAP

After you wake up, you’ll want to get into bright light right away. This is of utmost importance if you have issues falling asleep.

Bright light after waking will phase advance all aspects of your circadian rhythm. Meaning you’ll produce more cortisol after waking, and you’ll produce melatonin sooner in the evening.

  • Get bright morning light exposure: You want about 15-30 minutes of bright light exposure after waking. This is especially important for those of you with any issues falling asleep or waking up. If the sun is out, go outside and go for a walk. If it’s still dark outside because you work a 9-5 in the winter. Spend some time in the morning in front of or near a very bright source of light.
  • Expose yourself to infrared: Your body also requires exposure to infrared before ultraviolet (as the natural sun cycle provides) to properly prepare the body for UV radiation. If you can’t get outside in the morning sun, you can use a heat lamp or two.

  • Build your own light therapy lamp: Traditional light therapy lamps use very bright blue pump LEDs, which will wake you up, but are very unlike natural light. You can make your own light therapy lamp by using GE Sun Filled BR30 style LEDs. This will give off around 10,000 lux at 1 foot, putting it firmly in the light therapy camp, but with a much healthier, fuller light spectrum.
DIY light therapy lamp using five ge sun filled br30 bulbs
This is a DIY light therapy lamp using five GE Sun Filled BR30 LED bulbs. It’ll cost you around $70 to build this.

  • Light therapy on the go: If you drive a lot in the dark winter mornings, or just want to utilize light therapy in a more convenient on the go manner, Luminette is the best option around. They offer glasses, and a new driving compatible light therapy device!

Staying Awake During the Day

Gettin morning exposure to bright light is important, but the rest of your day cannot be spent in darkness either.

The Importance of Circadian Stimulation

Bright light is needed to set the human circadian “clock”. Since every single process in the body relies on this input, so it’s extremely important that you’re sufficiently exposed to light that can accomplish that.

The Lighting and Research Center (LRC) has developed a metric for this, called Circadian Stimulus (CS). You can read more about that here if you’d like.

graph comparing melatonin suppresion against circadian light
This graph made by the LRC is derived from nocturnal melatonin suppression studies, as they are the best available proxy for circadian stimulation in published literature. As you can see, both warm and daylight lux can stimulate the circadian system, with the biggest determinate being the brightness. (Source)

Now, it’s not very difficult to achieve the LRC minimum recommended CS of 0.3, and in my opinion, we should all be striving for a CS of 0.7+ during the day. The lux required to achieve this still pales in comparison to the brightness of even the darkest overcast day.

This is a bit harder to achieve and almost guarantees you’ll need to add a bit more light to wherever you spend a lot of time during the day.

Luminous Output Calculator

Using the calculator above, make sure your office lighting is hitting 100 fc. My personal office is actually over this, and I could comfortably go higher. This ensures a high CS without needing to do much calculations.

Get More Bright Sunlight Exposure

Daytime is all about bright sunlight. The more bright light exposure you have, the better your sleep will be. From waking up, to falling asleep, to staying asleep, bright light is the answer!

  • Spend as much time outside as you can: Regardless of how much light you bring into your indoor space, it will never match the raw power of the sun. Get outside as early and as often as you can, the more you do, the better your sleep will be.
  • Spend time near a window: At work or at home, try to get your office space as close to a window as you can, south facing windows are best. If this isn’t possible, then east is second best, as bright light in the morning is far more important than in the evening. Obviously avoid glare and any other uncomfortable issues that can arise.
  • Replicate sunlight where it’s needed: If you’re trapped indoors all day long, whether that’s at home or in your work cubicle, you need to make sure you’re getting bright enough light in your eyes to thoroughly activate the circadian response. My guide on How to Replicate Full Spectrum Sunlight Indoors is definitely worth a read if you think you might benefit from this.
  • Ditch the sunglasses: Suffice it to say that your eyes are perfectly adapted to UV exposure from the sun, and blocking sunlight will only lead to unintended and unknown biological side effects. Sunglasses can be potentially efficacious if you spend a considerable amount of time on snow or water, but otherwise, you’re not doing yourself any favors.
  • Wear a tan-through shirt: Get a tan-through shirt to use as an undershirt for work, when you go outside to eat lunch you can take your work shirt off without drawing much attention to yourself. While typical shirts let in 1% UVB, tan-through lets in 50%. The white is pretty see-through, so you may want to get a darker color.
  • Measure your vitamin D intake: UVB exposure is necessary to synthesize vitamin D3 sulfate, a water-soluble form of vitamin D3 that can travel freely throughout the body. You can track your vitamin D exposure with the D Minder app! It’s interesting to see and gives you an idea of what you’re likely getting.

Winding Down in the Evening

Finally, as our day comes to an end, it’s important that we respect this time as it would be in nature, and the message it has for us to slow down.

Limit Late Night Exercise

  • Intense physical activity within one hour of sleep may negatively affect sleep onset latency, total sleep time, and sleep efficiency. [R] [R]
  • Other than that, in general, exercise in the evening doesn’t appear to be associated with negative sleep outcomes or circadian phase delays. [R] [R] [R]

Keep Calories Low

It’s generally recommended to limit larger meals to earlier in the evening for various reasons.

  1. Glucose tolerance is limited following melatonin secretion. [R] [R]
  2. Gastric emptying is slower. [R]
  3. Resting metabolic rate slows. [R]

So ideally, the evening is not the best time to consume a large amount of calories.

However! There are studies and literature on evening meals and snacks not having much of a negative impact on healthy individuals.

  • When shifting the evening meal from 5 hours before bed to 1 hour before bed in 20 healthy adults, no disruption in sleep quality was found. [R]
  • Nighttime snack consumption does not appear to be detrimental, and may even be useful in some cases. [R]

That being said, it’s probably best to keep large meals 2-3 hours away from bedtime, but if you’re hungry before bed, you may find sleep comes easier and deeper if you indulge in a little snack, I know it does for me.

Lower the Temperature

This one is pretty simple, the temperature of your environment should gradually decrease as your bedtime approaches.

Just set your thermostat to drop by 5 degrees two hours or so before you’ll be nodding off.

  • Gradual changes of light and temperature both in the evening are associated with high melatonin levels in the morning and lower drowsiness upon waking. [R]

Warm Dim Evening Lighting is Important

As a general rule, it’s important that we keep our lighting dim and warm before bed.

  • In this study using a 4000K light source and around 50 participants, lux levels of just 10 were enough to suppress melatonin by 50% in some. While others did not reach 50% suppression until light levels reached 400 lux. [R]
  • In a study comparing red light exposure with bright white light, red light still phase shifted some people, with two participants shifting just as much as the bright light group. [R]
  • Circadian responses to 555 nm green light are too strong to account for just a melanopsin response, meaning that cone receptors contribute to circadian entrainment. [R]

Now, you’ll often see red and orange/amber lights recommended here. I personally find the spectrum from lights like this to feel very unnatural and unpleasant, and quite frankly, it’s unnecessary. They’re also typically much too bright and every single low wattage LED light bulb I’ve found has insanely high levels of flicker, which I’m not very comfortable with.

I’ve personally tested several of these light bulbs (you can find the test data here), and I’ve come to the conclusion that a C7 incandescent night light is where the party’s at, the slumber party that is.

Now before you ask… yes, incandescent lights give off some short wavelength light, but what’s important is this amount is so small that it has no meaningful chance of disrupting your melatonin secretion at night.

So here’s all the light you’ll need to get all cozy before bed:

  • Incandescent C7 Bulbs: These bulbs give off a really dim, warm (2200K) full spectrum light that will have you snoozing in no time. The 7w 50 lm bulbs are great for living rooms, kitchens, and bedrooms, while you might prefer the 4w 15 lm bulbs for bathrooms and smaller bedrooms. You’ll likely need an adapter to use these in standard light sockets.

  • Hooga Reading Light: The lights above aren’t bright enough to read by, so if you plan on doing any of that, you’ll need something else.

Mitigating Blue Light From Electronics

If you have any trouble sleeping at all, I recommend complete abstinence from electronics two hours before bed.

However, if you’re going to use them anyway, it should be done responsibly.

Below are some strategies for mitigating blue light from electronic devices:

  • Turn on night mode: Whatever your device, be it a Windows PC, MacBook, iPhone, or Android, it should be set to night mode two hours before you plan to go to bed. Below are some examples of what this does to the light output on your devices.
  • Darken your web pages: You can drastically cut down on blue light and the overall brightness emitted from your computer by installing Dark Reader on your web browser. This website has its own night mode, as you will have hopefully seen.
  • Block rouge LED light: Blue LED indicator lights should be made illegal, who’s with me?! Bring pure darkness back into your life by extinguishing all the annoying bright lights in it.
  • Download Lunar: If you own a MacBook, you owe it to yourself to get Lunar on it. Lunar gives you far more control over dimming, including the ability to auto dim external monitors in sync with your laptop.
  • Download IRIS: IRIS is an application that allows for better dimming control on Windows machines, which I consider essential. If you own a webcam, you can let IRIS use that for auto dimming, even if your computer doesn’t support such a thing.
  • Buy some blue blockers: It’s nice to have a pair of blue blockers for travel, late nights, or even at home if you have rather unhealthy roommates. The mainstream blue blockers are all really overpriced, so I recommend staying away from basically all of them. You can grab a pair for style points if you wish, of course.

  • Use amber screen filters: If you like to read at night with an electronic device, you might find it useful to attach an amber screen filter to it to mitigate the more energetic blue light. And remember to use it as dimly lit as comfortably possible!

Keeping Your Bedroom Dark

As you go to sleep, it’s important to keep your bedroom dark at night.

Natural night is extremely dark, and you don’t want any man-made light causing your body any confusion about what time of day it is.

  • Blackout your room: Make sure your room is blackout dark at night, you shouldn’t be able to see your hands move in front of your face. This is necessary above and beyond eye masks because even your skin has photoreceptors that can detect light. Use a combination of blackout shades and blackout curtains if you have to, the darker the better. When setting up curtains, use a wraparound rod. You can also use a draft stopper to block light from under the door.

Wear a sleep mask if necessary: If it’s still not dark enough in your sleeping environment consider using a sleeping mask, this may be necessary during travel or if you can’t get your room 100% dark. When it comes to sleep masks, I’ve found Manta makes the best one.

TLDR: Action Steps

This section is for those of you who either don’t have time to connect all the dots above, or just want a quick list of things that can be done to optimize your biology.

  1. Wake up around the same time every day with a dawn simulating light alarm clock.
  2. Expose yourself to bright light within 15 minutes of waking up for at least 10 minutes.
  3. Get all day bright light exposure, create your own light setups if necessary.
  4. In the evening, keep your exercise and meals light.
  5. Keep evening lighting very dim and warm, two hours before bed.
  6. Blackout your bedroom to keep artificial light from disrupting your circadian rhythm and sleep.

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