Can Morning Sunlight Bring Your Body Clock Forward?

The fourteenth variable that I will be manipulating across a two week period to examine its impact on sleep is light exposure. I will see if being obtaining at least 30 minutes of morning sunlight will have a substantial impact on my timing of sleep. 

I will discuss what my data shows, how easy or difficult I found this strategy to implement, and what previous research says. These three factors will be combined for an overall score and grade on how effective morning sunlight is at helping me get to sleep earlier.

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HOW COULD MORNING SUNLIGHT IMPROVE SLEEP?

If you look at my sleep in my temperature experiment, I was sleeping pretty well, but I was going to bed quite late, with an average time to bed of 12:05am. I said that 11:30pm-7:30am is probably my ideal time to be in bed, based on my internal body clock or circadian rhythm.

I’ve always been a bit of a night owl, and sleeping later is actually better for me than trying to force myself to go to bed too early. However, sometimes I have dreams of being able to get up and go to the gym before I go to work. I have, therefore, also studied different ways of how to effectively go to bed earlier and still sleep well.

The best way to do this, based on chronobiology research, is through the timing and duration of our light exposure. By getting even 30 minutes of morning sunlight shortly after awakening in the morning, this might really help me to start to feel sleepy earlier in the evening so that I can bring my bedtime forward without extending how long it takes me to fall asleep.

THE EXPERIMENT

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For the first six days, I tried to avoid getting sunlight as much as possible before noon and wore sunglasses whenever I did go outside in the morning.

For the next 8 days, I went on a cruise up and down the east coast of Australia. I tried to get outside as soon as possible after waking up and made sure that I got at least 30 minutes of sunlight exposure before noon.

Let’s see which strategy led to a better sleep…

THE OUTCOME

 

episode 14 sleep diary

Comparison: No Morning Light vs Morning Sunlight Exposure (at least 30 minutes)

Based on my sleep diary data, the findings were as follows:

  • The number of awakenings:
    1. No morning light – 0.66 per night
    2. Morning sunlight exposure – 1.88 per night
      • less is better
  • Time in bed:
    1. Morning sunlight exposure – 8 hours 29 minutes
    2. No morning light – 7 hours 18 minutes
      • 8 hours is ideal for me
  • Time to bed:
    1. No morning light – 11:29pm
    2. Morning sunlight exposure – 10:21pm
      • 11:30pm is ideal for me
  • Total sleep time:
    1. Morning sunlight exposure – 7 hours 47 minutes
    2. No morning light – 6 hours 50 minutes
      • 7 hours 30 minutes is ideal for me
  • Sleep onset latency:
    1. Morning sunlight exposure – 13.75 minutes
    2. No morning light – 20 minutes
      • quicker is better
  • Wake after sleep onset:
    1. No morning light – 7.5 minutes
    2. Morning sunlight exposure – 28.13 minutes
      • less is better
  • Rise time:
    1. Morning sunlight exposure – 6:50 am
    2. No morning light – 6:47 am
      • 7:30am is ideal for me
  • Sleep quality:
    1. No morning light – 4.5/5
    2. Morning sunlight exposure – 3.75/5
      • higher is better
  • Sleep efficiency:
    1. No morning light – 93.72%
    2. Morning sunlight exposure – 91.77%
      • higher is better

AND THE WINNER IS…

With a count of 5 points to 4 points, avoiding morning sunlight for me led to fewer awakenings during the night, less time awake during the night, and a better sleep quality and sleep efficiency. The poorer sleep on the second week could have had something to do with being on a cruise ship, however, rather than the morning sunlight.

What getting the morning sunlight exposure really did seem to help with was going to bed a lot earlier, as I went to bed at 10:21pm on average the second week, 68 minutes earlier than the second week. Even with this, I still managed to fall asleep 6 minutes faster than I did the first week!

 

IS SEEKING MORNING SUNLIGHT A GOOD SLEEP STRATEGY?

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IS IT EFFECTIVE?

Yes. Even though my sleep quality and sleep efficiency were worse, I put this down to trying to sleep on a cruise ship rather than the negative impacts of getting early morning sunlight. It seemed to help me feel energetic during the day, concentrate better, and fall asleep a lot earlier at night time.

I, therefore, give the effectiveness of this strategy a 17/25.

CAN IT BE APPLIED?

Yes. I often recommend for my clients to try and get 20 minutes of sunlight in the morning if they are wanting to fall asleep earlier.

It can be hard on weekdays, and harder in winter too, but most people can find some time, either whilst eating breakfast, walking the dogs or on their commute. It becomes a lot easier on the weekends and in the warmer months.

If it is too hard to find the time, blue-light glasses such as re-timer glasses can also be put on for 20 minutes as soon as people wake up for an easy to apply (but more expensive) alternative.

I, therefore, give the applicability of this strategy a 16/25. 

IS IT SCIENTIFIC?

Wright Jr. and colleagues (2013) have shown that reduced daytime sunlight and increased bright screen usage at night contributes to a delayed circadian rhythm and later sleep times.

Crowley and Eastman (2015) showed that a single 30-minute exposure to bright light in the morning was as effective as bringing an individuals body clock forward as getting one hour of bright light spread over a 3.25 hour period. It’s not quite as good as getting 2 hours of light exposure, but it can produce 75% of the advance and requires 90 minutes less time each day, which is much more practical for most people.

Stothard and colleagues (2017) have also found that a weekend camping can bring forward people’s circadian rhythm and sleep timing much more than a typical weekend for people living in a modern environment.

I, therefore, give the science of this strategy a 32/50.

Overall, morning sunlight as a way to sleep better gets a score of 17/25 + 16/25 + 32/50 =

65/100: Credit

 

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WHAT I RECOMMEND

Cruises are nice and relaxing and provide a lot of opportunity for getting some sun and not having to worry about anything, but they still didn’t lead to the best sleep for me.

If you are already sleeping at the right time for your internal body clock, then morning sunlight may not add too much of an additional benefit to you.

If you have a delayed circadian rhythm or find it difficult to get to sleep at the start of the night, getting 30 minutes of sunlight soon after you wake up in the morning could help you to wake up a bit quicker, feel more alert and energetic, and help you to get to sleep earlier and faster at night time.

Thanks for reading! If you would like a personalised sleep report and the five things that you could do to best improve your sleep, please check out our services.

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