Sleep Tracking: The Brain and Circadian Rhythm's Role in Sleep

Abstract

Everybody sleeps, but not everybody has good quality sleep. Sleep is essential for the brain, but how do our daily choices impact sleep? In this science project, you will experiment and explore factors that influence your nighttime sleep schedule. 

Summary

Areas of Science

Human Biology & Health

Difficulty

Method

Scientific Method

Time Required

Very Long (1+ months)

Prerequisites

None

Material Availability

Readily available

Cost

Very Low (under $20)

Safety

Adult supervision is required to discuss and approve sleep interventions. 

Credits

Laura Ohl, PhD, Science Buddies Alumni

Science Buddies is committed to creating content authored by scientists and educators. Learn more about our process and how we use AI.

https://www.youtube.com/watch?v=w2meaXDflFQ

Objective

To learn about the circadian rhythm and what impacts it by tracking your sleep and testing how daily choices influence your sleep.

Introduction

Neurons are everywhere in your body, allowing you to walk, write, think, digest food, read, and breathe. They have such an essential role in the body that we often forget that they control every aspect of our being. In our bodies, the highest density of neurons is in our brain, which is part of our central nervous system. For our nervous system to function well, it needs a break, just like you do after a long day of play. So, when does the nervous system get to take a break? During sleep! How does the body know when it's time for sleep? The circadian rhythm is our body’s internal clock that differentiates between when we should be asleep and when we should be awake in a daily cycle. Interestingly, new research has shown that our bodies don’t run on a 24-hour schedule, so correction with the presence or absence of light can help correct this misalignment with our circadian rhythm. That is why getting outside during the day is essential to help regulate and correct our nervous system's timeline for sleep. But what is sleep anyway?

Sleep is a complex biological process of unconsciousness, where our bodies have altered mental capabilities, physical movement, and specific senses. During sleep, the body cycles through different sleep stages associated with distinct brain waves. Brain waves are typically measured with devices called electroencephalogram (EEG). This device measures four different brain waves, and the body cycles through these different brain waves in different stages of sleep. On average, each sleep cycle lasts approximately 90 minutes. One of our brain waves is associated with wakefulness (beta), while the other three (delta, theta, alpha) are associated with different stages of sleep. Delta waves are the slowest waves, indicating our deepest, most restful, and restorative stage of sleep. Theta waves are our second slowest brain waves and represent our subconscious mind. They are also crucial in vivid dreaming during the rapid eye movement (REM) stage of sleep. Lastly, the alpha waves are associated with relaxation and very light sleep. With all this neuroscience brain wave knowledge, how can we use this information to help us track our sleep?

Personal wearable devices used for fitness tracking can't track our brain waves yet. However, there is another way to predict our sleep based on physiological measures. Our nervous system is integrated into and influences every inch of our bodies, including our muscles. During sleep, our brain regulates muscle tone or contractions, allowing them to tense or relax. How much or how little a muscle is contracted is measured with electromyography (EMG) in a sleep lab. Instead of using this complex machinery, we can use scientific knowledge that the brain temporarily paralyzes or prevents us from moving during sleep so we don't get hurt when our brain visualizes our dreams. Therefore, scientists have added an accelerometer to wearable devices to predict you are awake when you are moving and asleep when you are not moving. Although this helps differentiate between being asleep or awake, movement does not tell us what stage of sleep you are in. Most wearable devices also contain a heart rate monitor to determine what stage of sleep you are in. They measure your heart rate variability or the space between each heartbeat. Heart rate variability fluctuates the most between each stage of sleep. Therefore, wearable devices can predict when and how long you are in each sleep stage by measuring these two variables of human biological data (movement and heart rate variation). This biological data can then be correlated with the associated brain waves, as seen in Figure 1.

Image Credit: Laura Ohl, PhD / Science Buddies

Image of sleep tracking data with the associated sleep stages and associated brain waves.

Using biomedical, particularly genetic data, to inform our health care and medical choices is called personalized medicine. Personalized data created with wearable devices can help us track, maximize, and improve our sleep schedules. The only drawback to these devices is that they extrapolate or assume a lot of information using algorithms from a small amount of data like heart rate and acceleration. This makes them less accurate than precise laboratory instruments used in research labs and sleep studies. Sleep disorders, such as insomnia, can lead to many different medical problems. There are even diseases that are increasing in incidence with the aging US population, such as neurodegenerative diseases, which have been shown to have sleep disruptions that precede brain changes for decades before disease onset (link in the bibliography to learn more). Therefore, improving overall sleep quality is of great biological importance to our overall health and risk for these age-dependent diseases. 

Good sleep can make a huge difference in your physical and emotional health. Good sleep hygiene can help improve your sleep. Sleep hygiene is a set of practices that helps you improve your sleep quality, by tailoring your lifestyle and environment to fit your sleep schedule. These practices include a consistent sleep schedule, regular exercise, a wind-down or relaxing routine, and creating an ideal sleep environment (dark, quiet, soothing). You can also avoid things in your environment or schedule to improve your overall sleep quality, such as reducing napping, not eating large meals right before sleep, and limiting blue-light screen usage before bedtime. Although there are general guidelines on improving your overall sleep, sleep can be deeply personal for everyone. What factors do you think would have the most significant impact on your sleep? In this science experiment, you will monitor your regular sleep schedule for one week using a wearable device with sleep tracking. Then, you will test one change or intervention to your sleep schedule to see how it impacts it. 

Terms and Concepts

• Neurons
• Central nervous system
• Circadian rhythm
• Unconscious
• Sleep stages
• Brain waves
• Electroencephalogram
• Beta waves
• Delta waves
• Theta waves
• Rapid eye movement (REM)
• Alpha waves
• Wearable device
• Electromyography
• Paralyzes
• Accelerometer
• Heart rate monitor
• Heart rate variability
• Personalized medicine
• Insomnia
• Neurodegenerative diseases
• Sleep hygiene

Questions

• What is the relationship between neurons and the central nervous system?
• What is the circadian rhythm?
• How many brain waves are there, and which ones are involved in being awake or asleep?
• How do scientists measure brain waves in a research lab?
• How long does a single sleep cycle typically last? 
• In what stage of sleep do you dream?
• What two physiological measures do a personal wearable device measure that allows us to predict sleep stages?
• What is it called when we use personal health data with a physician to make decisions about our medical care?
• What human diseases are associated with sleep disruptions?
• How can you improve your sleep?

Materials and Equipment

• 1 participant for the personalized medicine approach or 10+ participants age 6 or above to compare your sleep to others (See our Sample Size guide on representative sample sizes.)
• Personal wearable device or fitness tracker with sleep tracking (must include heart rate monitoring)
  • We tested out this affordable option, and it worked well!
• Lab notebook or paper

This project follows the Scientific Method. Review the steps before you begin.

Experimental Background

Sleep can vary daily, particularly if you don't have a regular sleep schedule. In this experiment, you will create a regular sleep schedule and monitor your and/or participants' sleep. A regular sleep schedule starts and ends at the same time each day and is consistent with the recommended daily sleep schedule of about 8 hours. To create a baseline sleep schedule, you will maintain a regular sleep schedule for a week by going to sleep and waking up at the same time each day. During sleep, you will use your sleep-tracking personal wearable device to measure the time spent in each stage of sleep (deep, light, awake) and the total time asleep. You will then take the average of your weekly data. 

After the week of a regular sleep schedule, you will add an intervention (examples in the protocol below) during the day to see how it impacts your regular sleep schedule at night. Even with the intervention, you will attempt to keep your approximately 8-hour sleep schedule. Depending on how disruptive the intervention is, this may or may not alter your regular sleep schedule. Record how the intervention impacted your sleep and see which sleep stages are most affected. 

Tracking Your Sleep

1. Before you start your experiment, choose a regular sleep schedule. In your data table, like Table 1, write the target bedtime and wake-up time of your 8-hour sleep schedule. 
2. During sleep, you will use your sleep-tracking personal wearable device to measure the time spent in each stage of sleep (deep, light, awake) and the total time asleep. 
   1. Wear your personal wearable device with heart rate monitoring each night. 
   2. Record the amount of deep sleep, light sleep, awake time, and total time asleep each day for a week.
   3. Calculate the average amount of deep sleep, light sleep, time awake, and total time asleep from the weekly data for your regular sleep schedule. You can do this manually with the instructions below or use an online calculator. 
      1. Convert all of the times to minutes and then back to hours to get the average total number of hours asleep or the average time in each sleep stage per day. Remember, 1 hour = 60 minutes. Here’s an example:
      2. Convert all time to minutes using this formula:
         Time in hours and minutes * (60 minutes/hour)
         • 8h 20 min (day 1)
         • = (480+20 min) 
         • = 500 min 
      3. Add all of the daily sleep times together to get the overall time asleep over the total number of days using this formula:
         Total minutes asleep = Time day 1 + Time day 2 + Time day 3 + Time day 4 + Time day 5 + Time day 6 + Time day 7
         • Time day 1 + Time day 2 
         • = 8h 20 min (day 1) + 9h 0min (day 2)
         • = 500 min + 540 min 
         • = 1040 min for 2 days
      4. Convert the total time back to hours using this formula:
         Total hours asleep = Total time asleep / (60 minutes/hour)
         • 1040 min / (60 min/hour) 
         • = 17.33 hours 
      5. Take the average over the total number of days using this formula:
         Week average = Total hours asleep / number of days slept
         • = 17.333 hours / 2 days 
         • = 8.666 hours
         • = 8 hours and 0.666 hours
      6. Convert time back into hours and minutes using this formula:
         Fraction of time in hours * (60 minutes/hour)
         • = 8 hours and 0.666 hours * (60min/hour)
         • = 8 hours 40 min per day
3. After the week of a regular sleep schedule, choose a single intervention to try to disrupt this sleep schedule. Make sure to check with your parent that the intervention is safe for you.
   1. Examples of recommended sleep interventions:
      • Using a phone screen before bed for 30 minutes
      • A 30-minute afternoon nap during the day
      • 1 drink with caffeine (<100mg caffeine per day) in the morning
      • 20 minutes of exercise before bed 
      • Eating a snack right before bed
4. Observe how the intervention impacts your regular sleep schedule at night, attempting to keep your same 8-hour sleep schedule as before. 
   1. Wear your personal wearable device with heart rate monitoring at night. 
   2. Record the amount of deep sleep, light sleep, awake time, and total time asleep each day for a week.
   3. Calculate the average time for each measure.
5. Calculate the average proportion for each sleep stage compared to the total sleep time. Use the minutes to calculate the proportion of time in each stage. 
   1. Proportion of deep sleep = weekly average deep sleep / total time asleep
   2. Proportion of light sleep = weekly average light sleep / total time asleep
   3. Proportion of time awake = weekly average deep sleep / total time asleep
6. Create a new data table for each participant if multiple participants are being tested. 

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Volunteer #:                                                                      Target bedtime: Age:                                                                                  Target wake-up time:
Sleep Stages	Week 1: Regular sleep (h:min)	Average regular sleep proportion of each stage compared to total sleep time	Week 2: Regular sleep + intervention (h:min)	Average regular sleep  + intervention proportion of each stage compared to total sleep time
Deep Sleep	Day 1: Day 2: Day 3: Day 4: Day 5: Day 6: Day 7: Week average:		Day 1: Day 2: Day 3: Day 4: Day 5: Day 6: Day 7: Week average:
Light Sleep	...		...
Awake (during 8 hour sleep schedule)
Total time asleep

Table 1. A data table is used to monitor an individual's sleep stages

Tracking Your Sleep Compared to Others

1. Before including them in the sleep tracking experiment, ensure all participants can choose a regular sleep schedule and perform the intervention chosen.  
2. Once each participant has been informed of the study recommendations, have them complete the same sleep protocol as you did with the same intervention.
3. Compile the data, similar to Table 2, to see the average time asleep in each stage.

Working with Human Test Subjects

There are special considerations when designing an experiment involving human subjects. Fairs affiliated with Regeneron International Science and Engineering Fair (ISEF) often require an Informed Consent Form (permission sheet) for every participant who is questioned. Consult the rules and regulations of the science fair that you are entering, prior to performing experiments or surveys. Please refer to the Science Buddies documents Projects Involving Human Subjects and Scientific Review Committee for additional important requirements. If you are working with minors, you must get advance permission from the children's parents or guardians (and teachers if you are performing the test while they are in school) to make sure that it is all right for the children to participate in the science fair project. Here are suggested guidelines for obtaining permission for working with minors:

1. Write a clear description of your science fair project, what you are studying, and what you hope to learn. Include how the child will be tested. Include a paragraph where you get a parent's or guardian's and/or teacher's signature.
2. Print out as many copies as you need for each child you will be surveying.
3. Pass out the permission sheet to the children or to the teachers of the children to give to the parents. You must have permission for all the children in order to be able to use them as test subjects.

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Sleep stages	Average regular sleep	Average regular sleep + intervention
Deep sleep (h:min)
Light sleep (h:min)
Awake (during 8 hour sleep schedule) (h:min)
Total time asleep (h:min)

Table 2. A summary data table was used to monitor the average time of all volunteers' sleep stages.

Conclusion

• How challenging was keeping a consistent sleep schedule before adding an intervention? Were you able to maintain a regular sleep schedule with the intervention? 
• Did the intervention increase or decrease your total time asleep? Based on this, can you conclude whether the intervention positively or negatively impacted nighttime sleep?
• How much variability is there between each daily measurement in your regular sleep? What do you think this means for your circadian rhythm? 
• On days you got less total sleep (such as with the intervention), what stage of sleep was reduced the most and least, or were they all proportionally improved or reduced?
• Which brain waves were most impacted by the intervention? Use the sleep stages to infer what brain waves are reduced or increased.
• If you experimented with multiple volunteers, were all volunteers impacted similarly or dissimilarly by the intervention? Why do you think that is?

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Global Goals

The United Nations Sustainable Development Goals (UNSDGs) are a blueprint to achieve a better and more sustainable future for all.

This project explores topics key to Good Health and Well-Being: Ensure healthy lives and promote well-being for all at all ages.

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