The Science Behind Dawn Simulation

Dawn simulation is possibly one of the easiest ways to improve the quality of your mornings and align your circadian rhythm.

But what exactly is it? And how is it best done?

Let’s take a deep dive into the literature to see precisely what the benefits and best practices are!

Dawn Simulation is…Natural!

If you’ve ever been camping, you probably know the feeling of waking up naturally after the sun has risen, and the birds are chirping away.

You didn’t have work or any responsibilities so you didn’t set an alarm, you simply woke up once your body and the environment decided you should.

cartoon girl waking up to dawn sunlight

You also probably recall not feeling excessively groggy or having difficulty waking.

This is because, in the wild, we naturally experience dawn through our closed eyelids before waking up.

Shouldn’t we be mimicking this process for the best waking experience?

How Dawn Light Wakes You Up

One of the most notable benefits of using a sunrise alarm clock is its ability to significantly decrease sleep inertia.

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Sleep inertia is that dreaded feeling of grogginess and confusion that follows waking. This is what tricks many of us into falling back asleep instead of getting out of bed.

It does this in part, by raising our levels of cortisol while we’re still sleeping, which would naturally occur during the later part of our sleep if we were outside.

You see, cortisol is one of the major hormones that follows a 24-hour rhythm, peaking in the morning just slightly after we wake up.

This morning rise in cortisol has been termed the cortisol awakening response (CAR).

graph displaying cortisol levels throughout the day

It’s well known that bright light in the morning is capable of significantly increasing this response.

What is less well-known is that we can shift the CAR peak closer to our wake time, by simulating dawn sunlight!

This means that when you finally wake up, you’ll actually feel awake.

What a lovely idea!

Effects of Dawn Simulation on Cortisol

Only a few studies have looked at cortisol levels following dawn light, so let’s take a look at them:

The first study that I know of that looked into dawn simulations’ effects on waking cortisol took place in 2004.

This study involved 12 subjects who used either dawn simulation for 30 minutes or a control alarm clock.

So while the study wasn’t blinded or placebo-controlled, it was controlled.

What the researchers saw was a significant increase in cortisol at 15 and 30 minutes post-waking in the dawn simulation group.

post waking cortisol levels graph
Cortisol concentration levels between both groups

It should also be noted that the arousal scores of the dawn group were much higher as well:

In 2010 another study was completed that looked at cortisol, sleep inertia, and skin temperature.

This study involved 16 subjects who once again used 30 minutes of dawn simulation light before an audible alarm, followed by 30 minutes of 300 lux light.

While the control group in this study simply received 30 minutes of 300 lux light following their alarm.

The authors were unable to find a significant difference in cortisol levels between these two groups, however.

Since we know that morning light increases cortisol, this could be due to the post-waking light in the control group overpowering any significant increase the dawn simulation group gained in waking cortisol.

However, even though any changes in cortisol were erased, the dawn simulation group still saw a significant improvement in sleepiness and subjective activity post-waking.

dawn vs control group sleepiness graph
subjective sleepiness scores
subjective activity graph between control and dawn light group
subjective activity scores

One last study completed in 2014 looked at cortisol differences in 18 subjects who either received dawn light or a dim light control.

This study was designed to measure neural cardiovascular changes following abrupt wake-ups versus a more gradual dawn wake-up, but they also measured cortisol 30 minutes after waking in both groups.

They found cortisol to be significantly higher in the dawn simulation group, similar to Thorn’s 2010 paper above.

The stress response to waking was also significantly decreased in the dawn light group which translated to a decrease in heart rate upon waking as well as an improved HRV upon waking.

heart rate and cortisol graph

Effects of Dawn Simulation on Sleep Inertia and Performance

Since one of the biggest benefits of using a sunrise alarm clock is better wake-ups, let’s go over some more research on this particular endpoint.

This first study was completed in 2010 and involved 23 subjects and two separate experiments.

The first experiment split the participants into three groups:

  1. 30 minutes of dawn light peaking at 50 lux
  2. 30 minutes of dawn light peaking at 250 lux
  3. 0 lux control

The researchers found that sleep inertia and mood were significantly better in both the 50 and 250-lux groups, but not the control

sleep inertia durations in control, 50 and 250 lux groups
subject mood levels between control, 50 lux, and 250 lux groups

In the second experiment, participants were allowed to select their preferred lux level, ranging from 20-400 lux.

The average lux chosen by participants was 265 lux which is interesting to note, as generally speaking most studies employ 250 lux light.

Another study completed in 2010 involved over 100 children who spent one week waking up with dawn simulation, and one week without.

During the dawn wake-up week, children felt more alert at awakening, got up easier, and reported higher alertness during the second lesson at school. Evening types benefited more than morning types.

A study from 2014 involved 8 subjects who all self-reported as late chronotypes and experienced large amounts of sleep inertia.

Two sunrise alarm clocks peaking at no more than 300 lux were placed on either side of the beds of participants.

Ratings of alertness and perceived sleep quality were higher, and cognitive performance, reaction time, and athletic performance were all higher in the dawn light group.

Another 2014 study done on 56 adolescents found that just 20 minutes of dawn light was enough to improve cognitive ability even several hours after waking.

Other than sleep quality and sleep inertia, can dawn simulation directly impact the circadian rhythm of humans?

Phase Advancing the Circadian Rhythm

The human circadian phase averages out to around 24.2 hours.

Thus, we require daily signals in the form of environmental light to set our circadian rhythm to a proper 24-hour cycle.

Well, it turns out that dawn simulation alone is capable of doing this!

In 2010 a rather large trial took place (relatively speaking) with over 100 subjects split into 5 groups.

We’re going to focus on two of the groups:

  1. 93 minutes of dawn light peaking at 250 lux
  2. 30 minutes of 10,000 lux light within 10 minutes of waking

Researchers were surprised to find that dawn light peaking at just 250 lux seemed to be just as effective at phase shifting the participants as 10,000 lux after waking was.

This could be due to the timing of the phase response curve to light. Which is most sensitive in the 2-hour window before awakening.

A greater amount of bright light exposure is required to achieve a similar effect as the morning progresses and sensitivity declines.

graph showing melatonin shift in bright light vs dawn groups

Winter Depression and Seasonal Affective Disorder

Sunrise alarm clocks have also been studied for their ability to lessen the symptoms of winter depression.

And it turns out they’re quite good at it!

The best part about these studies is that there are quite a few of them and they employ placebo controls and various durations and brightness levels.

This allows us to get a better idea of what we might want to emulate for the best waking experience.

The first studies I could find using dawn simulation to study the effects of winter depression began in 1992, the year I was born!

This first study was a 4-week randomized crossover trial in which 9 participants spent 1 week using a 2.5-hour dawn and 1 week using a 10-minute dawn.

Both dawns had a peak illuminance of 275 lux.

Decreases in depression were similar in both groups, however, in the gradual 2.5-hour dawn group, 7 out of the 9 participants complained of early awakening, whereas in the 10-minute dawn group, only 1 out of the 9 complained of having this issue.

Another study used a crossover design in which participants were split into two groups:

  1. Bright light therapy for two hours after waking at 1700 lux
  2. Two-hour dawn peaking at 1700 lux

In the dawn simulation group, all of the subjects experienced mild awakening with half of them labeling it as severe.

dawn simulation study results early awakening

It would appear as though two hours of 1700x lux is a bit too much!

This is a small study, but the researchers concluded that while the dawn was effective in reducing depression it didn’t work as well as the bright light therapy.

A slightly larger study was done in 1993, this one using 16 participants split into two groups:

  1. A slow 45-minute halogen sunrise peaking at 100 lux.
  2. A quick 4-second rise to 100 lux

The slow dawn group saw much better results than the quick dawn, while 4 participants found the quick dawn itself to be uncomfortably abrupt.

results from rapid vs slow dawn simulation study
Results from the study

Another study completed in 1993 recruited a total of 22 participants and split them into two groups:

  1. 1 week of a 2-hour dawn simulation peaking at 250 lux.
  2. 1 week of a 30-minute dawn simulation peaking at 0.2 lux.

Both the Hamilton depression scores and the seasonal affective disorder subscale scores were significantly lower in the 2-hour dawn group than in the 30-minute placebo group.

dawn simulation study results

One out of the 13 participants in the 2-hour dawn group reported hypomania.

In 1994, another interesting placebo control trial was completed with 19 participants.

The participants were split up into two groups:

  1. 1 week of a white 1.5-hr dawn simulation peaking at 250 lux.
  2. 1 week of a red, 1.5-hr dawn signal peaking at 2 lux.

This study employed red light as its placebo control.

The bright white dawn had a significantly better effect on reducing depression scores via the Hamilton Rating Scale for Depression.

A few of the white dawn subjects did experience early awakenings here as well.

winter depression study results

A study from 2001 consisted of 95 subjects split into three groups:

  1. Bright light therapy 10,000 lux for 30 min
  2. Dawn simulation 1.5-hour dawn signal peaking at 250 lux
  3. Dim red light 1.5-hour dawn signal peaking at 0.5 lux

The three groups were studied for a total of 6 weeks.

Unexpectedly, in this study, dawn simulation was more effective than both the placebo and the bright light group in causing remission of seasonal affective disorder.

graph showing response rates to various interventions

Another 2006 study enrolled 99 adults and once again compared bright light therapy to dawn simulation (among other interventions).

The dawn simulation was 3.5 hours long and peaked at 250 lux, while the bright light therapy was set to 10,000 lux and took place for 30 minutes after waking.

The study intervention period was 3 weeks.

depression and seasonal effetive score table from 2006 study

Bright light therapy was a bit more effective than the dawn simulation in this study, but it should be noted that they were both effective.

One final study I could find from 2015 once again compared dawn simulation with bright light therapy.

This study enrolled 40 participants with seasonal affective disorder and split them into two groups:

  1. 1 week of bright light at 4,300 lux for 30-45min shortly after awakening.
  2. 1 week of 30-minute dawn simulation peaking at 100 lux before alarm beep, with the dawn simulator placed closer to the open eyes for a further 15 minutes at 250 lux.
dawn simulation vs bright light therapy preferences chart

Overall, the bright light therapy seemed to work a bit better, but they were both fairly effective.

It was noted that those who preferred bright light therapy tended to have worse depression, and saw more benefit from the bright light treatment than the dawn light.

Of those that preferred the dawn light therapy, time savings, and naturalness were the biggest factors.

Conclusion and Takeaways

Here’s what we know about dawn simulation:

  • It significantly reduces sleep inertia complaints and improves sleepiness, cognition, reaction time, and perceived sleep quality.
  • Even in the absence of morning light after waking, dawn light can shift circadian timing, making it valuable to anyone with insomnia, delayed sleep phase disorders, or anyone looking to optimize their circadian rhythm.
  • It can be just as effective as much brighter light therapy following waking, making it a very useful adjunct to those with depression or seasonal affective disorder.

Here’s how to use dawn light:

  • Most studies run their dawn simulation for 30 minutes prior to waking followed by an audible alarm, however, studies include an audible alarm only because they need consistent timing.
  • Studies used dawn light for 10 minutes all the way up to 90 minutes. And various participants found these times preferable. So start with 30 minutes, but explore increasing or decreasing this timing to find your preferred setting.
  • It’s worth noting that while some people seemed to get better results from longer dawn periods i.e. 90 minutes, other people experienced severe early awakenings from this same timing. You’ll have to experiment to find your Goldilocks zone.
  • Dawn simulators used in studies usually peak at around 250-300 lux at the head. This can be achieved by placing your lamp at head level around 1.5 – 2 feet away from your pillow.
  • We will be scientifically reviewing several of the leading sunrise alarm products soon in order to get this data at various distances, so keep an eye out for that!

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  1. Do you have any recommended products in this area?

    Or do you recommend a way to automate some of your other recommended lighting solutions so that they function as a wake-up light?

    Thank you for everything!

    1. Hi Taylor! Unfortunately, I haven’t yet embarked on my quest to test and review sunrise alarm clocks, but I really want to so hopefully I’ll do that before December ends.

      For now, it’s hard for me to recommend something simply because I don’t have objective data and experience with them all. But I’ve personally really liked the Philips HF3650 as it starts off very dim and red, and has a lot of settings for varying the sunrise time.

      There are cheaper ones you can try out though! The other option is using smart lights, however many of them don’t get very dim, I’m still testing a lot of those so hopefully I’ll find some that will work great for this purpose!

      Stay tuned! The dawn simulation knowledge and recommendations will hopefully get a lot better here soon.