What is Impacting your Sleep

In the previous article we discussed the mechanisms and the impact that stress can have on your sleep. In the next couple of articles we will discuss what the key stressors in your life are and how they impacting your sleep.

 

  • Mental & Emotional:

Mental and emotional stress is the most common stressor, so it makes sense to start here. This is a common issue when trying to get to sleep, especially if you are a ‘Worrier’ or you are a A-Type personality who is always on the go and unable to sit still.  I like to call this group “tired and wired”. When they lie down at night their minds are wired with endless thoughts with an inability to shut these down (this used to be me…) making it extremely difficult to get to sleep.

But did you know, this is more than just the cognitive load keeping you awake, there is an associated hormonal response. Towards the end of our previous post we discussed the stress related increase in cortisol and how it is preventing the secretion of your sleep hormone melatonin (the inverse relationship discussed in stressed out about sleep)

Strategies to overcome emotional and mental stress:

Implement a 1 hour cut off of all technology before sleep. Instead replace the time on your mobile device with a down regulation technique. Some examples include:

  • Mindfulness Practice: I use Headspace a guided practice
  • Breathing Practice: My favorite downregulation technique: Breath in for 4 sec – Hold 7 sec – Exhale for 8 sec and repeat as many cycles as needed
  • Mediation Practice: Find a technique that works for you
  • Light exercise: Yoga / Mobility / Walking
  • Exposure to Nature & Grounding: Get outside away from light where possible
  • Read a book: Leasure reading, Non cognitive or stimulating
  • Cold Shower the effect on decreasing body temperature increases the parasympathetic nervous system encouraging you to relax.

 

  1. Exercise:

Sleep is the best performance hack for physical performance, so don’t compromise your sleep for training. However the timing of this training does matter.

Exercise can cause a potent circadian shift, almost to an equivalent level of bright lights.

Strategies to use exercise to encourage sleep:

Including some form of light exercise (eg. 10-45 min) prior to breakfast to really help to kick start your day. A tip is to keep it relatively short and not too intense as you may wish to avoid amplifying the natural elevation in cortisol that occurs in the morning. Something like yoga, mobility, walk, recovery session are perfect options, for an added benefit try linking this session with exposure to natural light (sun) to improve awakeness. Simply put get outside early and move. Where possible try leave your longers volume based sessions for the early afternoon. Sessions (up to 2.5 hours long) between 2:00-6:00 pm at 50-80% VO2max can drastically improve sleep. The most positive 

effects have been seen within a 4-8hr window prior to bedtime. If you have a short 30 min high intensity session (85–90% of max HR to exhaustion) save this for 3-4 hrs before bed as it can actually result in better sleep, increased sleep efficiency and lower sleep latency.

Obviously lifestyle demands and work schedules don’t allow us to truly match up our training to ideal times, instead most people will squeeze in their training wherever possible. However, hopefully by arming you with this knowledge, it can help guide your training schedule to optimise your sleep quality. 

 

 

  1. Fueling your Sleep (Nutrition & Snacking):

 Increased body mass index (BMI) has been linked to short sleep duration. In one study, the researchers sought to identify why this effect of BMI and sleep occurred. The results indicated that shorter sleep duration decreased Leptin (the appetite suppressing hormone secreted by adipose/fat tissue) and increased Ghrelin (appetite stimulating hormone secreted from the stomach). These results provide evidence that sleep quality has a part to play with increased BMI. So lack of sleep can be increasing your hunger and be increasing your BMI, so your change in body weight may not be fully due to a lack of willpower but triggered by a hormonal responses.

Let’s get to know our hormonal responses:

Note: This is a little more technical for the science geeks like me, who want to understand the physiological mechanisms at play.

In the evening, leptin is released from your fat stores, well that is if your circadian rhythm is not dysregulated. This hormone is important as it controls any late night food cravings you may experience. Anything that throws your circadian rhythm off eg. exposure to blue light or an excessively big meal (spiking that insulin response) can limit your bodies ability to produce leptin. Another key hormone; adiponectin also tends to rise during this time and assists with fatty-acid metabolism and breakdown. 

High levels of insulin have been shown to dampen adiponectin production. Constantly high circulating levels of insulin from a high calorie evening meal or lack of activity in the late afternoon or early evening, can suppress your night time fatty acid utilisation. Then around 10 pm a protein called agouti peaks, it appears to act in similar fashion to ghrelin and can stimulate your appetite. That is unless leptin is there to mitigate the effects and keep hunger at bay. Constant snacking from sunset to bedtime promotes an elevated blood glucose response and inturn high insulin levels which causes a subsequent suppression in leptin and inability to counteract the effects of agouti protein.

Normally at midnight, your melatonin peaks and that’s when leptin is able to enter an area of the brain called the hypothalamus, or  the ‘god-father’ of the endocrine system. The hypothalamus is a key regulator of all metabolic processes and therefore has a role in weight-control or fat-loss. Leptin can interact with the hypothalamus, as a result of this interaction signals are sent from the hypothalamus to the thyroid and an increase in thyroid hormones is observed. The increase in thyroid hormone activity induces a change in your mitochondria (intracellular powerhouses) to produce heat, this is important as our body’s core temperature drops throughout the night. In a healthy individual this would mobilise and burn fat stores to maintain a set point of warmth.

 

Why are we fat?

You are probably starting to see the vicious cycle of poor sleep; there is fat gain and night time cravings. It all seemingly stems from hormonal responses, and once you understand these physiological mechanisms it becomes a lot easier to combat and overcome.

In this discussion gut health can not be forgotten, as obviously poor gut health can be a key contributor to stress. An, interesting fact we now know is that 90% of your feel good neurotransmitter, serotonin is produced in the gut.  This is just another reason to prioritise your gut health. The Pineal Gland is located near center of the brain and is also known as the ‘third eye’ due to the organs ability to sense light. It was named due to the shape and size of the gland as it resemble a Pine Nut and secretes melatonin. However, it has now been discovered that 400 x more melatonin is produced in the gut. Even if your pineal gland is removed, your body is still able to maintain the same levels of melatonin. So it is key to ensure you have optimal gut bacterial balance and should avoid damaging your gut in any way to ensure optimal sleep.

Strategies based on the timing of eating to improve sleep quality:

When looking at the evidence, further research is required but my interpretation and what I practice personally is to ditch the carbohydrates, or at least minimise them especially your highly processed carbohydrates (i.e. your high sugar high GI foods). Shift your diet towards higher fat which will nourish and stabilise your hormones resulting in less spikes and crashes in insulin and energy which will inturn improve circadian rhythm and your sleep and help keep your cravings at bay. (for more information around high fat diet all last month was focused around this area with 8 blog posts to help you gain a greater understanding)

I need to snack options!

As mentioned we want to limit snacks especially on carbohydrates in the evening. Incidentally, if you need something there are many great options, such as coconut oil, MCT oil, nut butters, seeds and nuts. Even fructose from a source such as raw honey in moderation will not actually spike insulin significantly and would be an acceptable evening calorie source.

 

Summary

Hopefully loaded with new information about lifestyle stressors will allow you to become more aware of the factors in your life that will be impacting your sleep. Being able to identify what is a key stressor in your life is critical to improving sleep and will allow you to select and implement the right strategy. There will always be an individual approach and may require some trial and error until you find the strategy that works best for you.

 

Key takeaways:

  • Develop Evening Routine that removes technology 1hr before bed that involves a downegulation technique in replacement
  • Develop Morning Routine light movement 10-45min (Yoga, Mobility, walk) with sun exposure
  • Schedule Longer Training Sessions (up to 2.5 hours long) between 2:00-6:00 pm at 50-80% VO2max
  • No Snacking Before Bed to maintain hormone balance but if required select High Fat sources eg coconut oil, MCT oil, nut butters, raw honey, seeds and nuts

References:

Banno, M., Harada, Y., Taniguchi, M., & Tobita, R. (2018). Exercise can improve sleep quality : a systematic review and meta-analysis. PeerJ. https://doi.org/10.7717/peerj.5172

Chen, C., Fichna, J., Bashashati, M., Li, Y., & Storr, M. (2011). Distribution , function and physiological role of melatonin in the lower gut. World Journal of Gastroenterology, 17(34), 3888–3898. https://doi.org/10.3748/wjg.v17.i34.3888

Connor, H. O., & Chow, C. (2007). High-glycemic-index carbohydrate meals shorten sleep onset 1 – 3. American Journal of Clinical Nutrition ·, (March), 2–7. https://doi.org/10.1093/ajcn/85.2.426

Halson, S. L. (2014). Sleep in Elite Athletes and Nutritional Interventions to Enhance Sleep. Sports Medicine, 44, 13–23. https://doi.org/10.1007/s40279-014-0147-0

Hu, W., Li, J., Colwell, C. S., & Zhou, Q. (2011). Decreased REM Sleep and Altered Circadian Sleep Regulation in Mice Lacking Vasoactive Intestinal Polypeptide. Sleep.

Kadowaki, T., Yamauchi, T., Kubota, N., Hara, K., Ueki, K., & Tobe, K. (2006). Review series Adiponectin and adiponectin receptors in insulin resistance , diabetes , and the metabolic syndrome. The Journal of Clinical Investigation, 116(7). https://doi.org/10.1172/JCI29126.1784

Markaki, A., Kyriazis, J., Stylianou, K., Fragkiadakis, G. A., Perakis, K., Margioris, A. N., … Daphnis, E. (2012). The role of serum magnesium and calcium on the association between adiponectin levels and all-cause mortality in end-stage renal disease patients. PloS One, 7(12), e52350. https://doi.org/10.1371/journal.pone.0052350

Mikic, A., & Pietrolungo, C. E. (2016). Effects of Diet on Sleep Quality 1,2. American Society for Nutrition. https://doi.org/10.3945/an.116.012336.SOL

Peuhkuri, K., Sihvola, N., & Korpela, R. (2012). Diet promotes sleep duration and quality. Nutrition Research, 2. https://doi.org/10.1016/j.nutres.2012.03.009

Premkumar, M., Sable, T., Dhanwal, D., & Dewan, R. (2013). Circadian Levels of Serum Melatonin and Cortisol in relation to Changes in Mood , Sleep , and Neurocognitive Performance , Spanning a Year of Residence in Antarctica. Neuroscience Journal, 2013.

Prinz, P. (2004). Sleep, Appetite, and Obesity—What Is the Link ? PLoS Medcine, 1(3). https://doi.org/10.1371/journal.pmed.0010061

Robey, E., Dawson, B., Halson, S., Gregson, W., Goodman, C., & Eastwood, P. (2014). Sleep quantity and quality in elite youth soccer players: A pilot study. European Journal of Sport Science, 14(5), 410–417. https://doi.org/10.1080/17461391.2013.843024

Robey, E., Dawson, B., Halson, S., Gregson, W., King, S., Goodman, C., & Eastwood, P. (2013). Effect of Evening Postexercise Cold Water Immersion on Subsequent Sleep. Medicine & Science in Sports & Exercise, 1394–1402. https://doi.org/10.1249/MSS.0b013e318287f321

Robey, E., Dawson, B., Halson, S., Gregson, W., King, S., Goodman, C., & Eastwood, P. (2013). Effect of evening postexercise cold water immersion on subsequent sleep. Medicine and Science in Sports and Exercise, 45(7), 1394–1402. https://doi.org/10.1249/MSS.0b013e318287f321

Steiger, A. (2003). Sleep and endocrinology. Journal of Internal Medicine 2003;, 13–22.

Taheri, S., Lin, L., Austin, D., Young, T., & Mignot, E. (2004). Short Sleep Duration Is Associated with Reduced Leptin , Elevated Ghrelin , and Increased Body Mass Index. PLoS Medcine, 1(3). https://doi.org/10.1371/journal.pmed.0010062

 

Stressed out about Sleep

Stressed out?

Stress is wreaking havoc on your sleep!

Sleep

Sleep is a complex physiological process involving the restoration and renewal of the body. I feel from my many conversations with people and clients that the concept of sleep and good sleep is commonly misunderstood. Many view sleep as a passive shutdown process, however, while we sleep our bodies are actually active. During sleep our bodies are cleaning up cellular garbage, repairing your body, processing of experiences and the consolidation of memories. Your sleep is dictated by what we call our circadian rhythm, it is basically a 24-hour internal clock that is running in the background of your brain and cycles between sleepiness and alertness at regular intervals. It is a mechanism that can be greatly altered due to a number of lifestyle factors. Anything that dysregulates your circadian rhythm will in turn be detrimental towards sleep quality.

 

What is stress and how does it affect your sleep?

If we are going to discuss good sleep and how to achieve it, one of the first things we will need to cover is stress and the major effect that the various forms of stress can have on your sleep.

Stress can be considered anything that places additional load on the human body. Stress is commonly discussed in the context of mental and emotional stressors, for example, “I am stressed out with my massive workload” or “ I am feeling very worried about my mothers health”. However, we also need to acknowledge other factors such as diet, injury, alcohol that can add additional stress. These are factors that are typically not identified or discussed but are all equally associated as stressors on our bodies.

 

Adrenal Fatigue Bell Curve:

In the early phase, when your body is exposed to chronic stress you may find it hard to fall asleep and often will wake up early before your alarm. On the other side of the bell curve, on that slippery downward slope, when you are severely and chronically stressed, you may fall asleep as soon as your head hits the pillow and wake up feeling groggy (bit like a good hangover feeling) and want to sleep past your alarm. This is because the body is now in a deep state of chronic adrenal dysregulation and your cortisol and melatonin are not functioning well, and as a result your circadian rhythm is muddled up. While I have discussed adrenal function and fatigue in a previous post there is one important concept I would like you to remember with regards to the effect of stress on sleep. The concept is: cortisol has an inverse relationship with melatonin (sleep hormone). Therefore when cortisol is high your melatonin is low and when low this will decrease ability to get to sleep and most of all quality of sleep (as seen in this diagram below)

Stress can be derived from four main factors:

  1. Lifestyle: Negative habits such as going to bed late or something as simple as not drinking enough water.
  2. Metabolism: Your current diet & digestion
  3. Environmental: Electromagnetic radiation from devices (mobile phones, laptops, ipads)
  4. Mental & Emotional: Excessive mental and emotional load.

 

All of these have a similar effect on your body and induce the upregulation of your stress hormone cortisol. I have discussed  cortisol and it impact when dysregulated in previous posts.

It is vital to be able to regulate your stressors to allow the body to regain a natural sleep cycle. To do this you must first identify your lifestyle stressors. These will vary greatly from person to person. In the context of this article it is difficult to offer you a detailed approach, as an individualised approach is needed for each person. As general rule of thumb if you are dealing with stress your need to find a way that will allow you to down regulate the stress in your life, or preferably remove the stressors all together.

 

What you need to keep in mind is that there is an endless number of stressors that may be affecting your sleep In the last article we discussed the environmental stressors from technology. In the next article we will aim to dive deeper into other key stressors, including mental, emotional and lifestyle factors. As we discuss them what you will notice is that there is a lot of overlap across them.

Sleep & Technology: How is it Effecting your Sleep?

In this next series of articles, we will be discussing some of the key factors that are affecting your sleep quality. My goal is to highlight factors that you may not be aware of and discuss their importance. This will then be followed by giving you actionable strategies to correct them and overall aim to improve the quality and maybe the quantity of sleep you are getting.

In this article we will be focusing on technology (phones, laptops, ipads- basically anything with a screen) and how it is affecting your sleep and offer you strategies to combat the screen time effects.

Now in the ‘good old days’ prior to the use of artificial lighting, the sun was the major source of lighting. So people would spend their evenings in (relative) darkness. Today, our modern electronic devices, and appliances have seamlessly integrated into our daily and night-time lives. Many of us will happily state that we are reliant on these devices, so much so that they are always with us, even when we sleep. Now across the world our evenings are artificially illuminated, the benefit is that it offers us the ability to dictate our own sleep cycles and the negative is that we neglect our primal circadian rhythms. With limitless light we often now find ourselves working long into the night/morning to meet a deadlines or we just get hooked on the new Netflix series.

Children in the United States are spending more than 53 hours/ week on technological devices! Often in this time frame they are using multiple devices at one time! The research that is investigating the effect of technology and sleep has indicated that this prolonged screen time could be one of the most significant factors in the increasing number of sleep problems, particularly the delayed sleep phase within the youth population.

 

Problem 1:

When it comes to light, blue light is key culprate for keeping you wide awake at night. Blue light suppresses your melatonin production (sleep hormone). Blue light has been shown to be great in heightening reaction time and alertness as it stimulates your mitochondria (cellular powerhouses). However, research has also suggested that it can cause cell dysfunction and this may contribute to cellular aging, age-related pathologies, and tumorigenesis.

Newer artificial lights lack many of the sun’s frequencies that our bodies and brains need. Artificial lights, have eliminated most of the infrared, red, and violet light found in natural sunlight, and are amplifying the blue light beyond anything we have evolved to handle. Most LEDs and compact fluorescents emit about 5 times the blue light we are used to. This is due to the fact that this form of  lighting being considered easy for the human eyes to see and it is extremely efficient in comparison to warmer lighting.

Interesly it was recently shown that there is a gender difference in light sensitivity. Men are more responsive and effected by the blue-enriched light in the late evenings, even with very low light levels (40 lux) compared to females. Therefore, it would appear that females are not impacted as seriously as males.  So men should be especially aware of this! However this research is still in the early days, but something to consider nonetheless.

 

Problem 2:

The great majority of the population today are attached to their devices, in particular mobile devices. We are never far from them even when sleeping. Harmless right? Sadly this is not the case, as it can cause sleep deprivation, depression and even emit radiation.

 

How?

Beyond the effects of blue light, our devices emit EMFs (Electromagnetic Fields), wireless energy waves that surround electronic devices. Specifically, these are artificial EMFs since they’re created by human technology. According to the World Health Organisation, EMFs have an effect on us since our bodies have their own electric and biochemical responses so much so they categorised as radiofrequency electromagnetic fields that are carcinogenic to humans (Group 2B).

EMFs present even more potential harm to our youth as they poses thinner skulls, allowing for greater penetration of cell phone radiation, enabling it to get as deep as their midbrain where tumors are more fatal. Plus children during growth have quick cell reproduction which means they are more receptive to progressive cell growth, good or bad. Beyond this children will be faced with greater longer term exposure as most adults over 50 years lived in a time without cell phones and/or were not exposed to them as children. To put in perspective a Swedish study concluded individuals who started using mobiles as teenagers, and have done so for at least 10 years, were 4.9 times more likely to develop astrocytoma (a form of cancer in the brain), compared to controls (people who had not been as readily exposed to mobile phones in their youth).

 

Problem 3:

I would be remiss if I did not state the potential effects that technology has to promote your pleasure and stress sensors. With our 24/7 world we can not escape stressful emails and messages that can bombard us just as we are set to down regulate and go to sleep. Even with blocking blue light an action packed Netflix series or movie can over stimulate your system preventing you from falling asleep. All of these factors can play a significant role in up-regulating your stress hormone cortisol which has an adverse relationship with the sleep hormone melatonin. This means melatonin is getting down regulated (reduced), leaving your body wired and unable to sleep.

 

Strategies/ Solutions:

I am not saying that you have to go full primal on me and use no technology and rise and fall with daylight. I am just suggesting we approach our sleep with great importance, prioritising it over technology and use our technology intelligently. Remember even if you don’t think these things are affecting you as you fall asleep, remember falling asleep doesn’t necessarily mean good quality sleep

 

Potential Strategies:

  • Create a evening/night-time routine
  • Apply Bluelight filters to all technology from sundown, most smartphones have this ability or download an app like F.Lux (I personal leave on 24/7)
  • Wear blueblocking glasses in evening especially when on devices (these have orange lenses)
  • Remove all technology one hour before bed, Instead: Read a physical book (non stimulating), do some low level mobility, talk to a loved one or mediate
  • Remove all devices or turn them on to airplane mode while sleeping and place them as far away from you as possible.
  • Cover any lights within the room eg Charging LED lights or TV etc.
  • Purchase a EMT monitoring devices so check levels within your room and house, you may be surprised the amount your devices are emitting.

References:

Health, N. I. of. (1979). Click in any of these pages to return to EMF and other environmental topics. National Institute of Health, (3), 5–8.

Hardell, L., & Carlberg, M. (2009). Mobile phones , cordless phones and the risk for brain tumours. International Journal of Oncology, 5–17. https://doi.org/10.3892/ijo

National Institute of Environmental Health Sciences. (2002). Electric and Magnetic Fields Associated with the Use of Electric Power. National Institutes of Health, (June). Retrieved from https://www.niehs.nih.gov/health/materials/electric_and_magnetic_fields_associated_with_the_use_of_electric_power_questions_and_answers_english_508.pdf

Ziskin, M. C. (2002). Electromagnetic hypersensitivity-a COMAR technical information statement. Engineering in Medicine and Biology Magazine, IEEE (Vol. 21). https://doi.org/10.1109/MEMB.2002.1044194

Sleep Month: How is your Sleep?

Sleep is the most important factor that underpins everything, if you are not sleeping you are sacrificing your health, well-being, longevity and performance (both work and sporting).

Being good at sleep is not like being good at sport or business, you don’t win any awards for being a great sleeper! Sleep is something that is traditionally private, until it being bad at it begins to seep into other areas of your life, such as when your health begins to decline or your focus starts wavering while at work.

Some will use lack of sleep as a badge of honor, stating that they can train, work, and be more productive with all the spare time gained from not sleeping. We all know these people that claim the amount of hours of sleep that they don’t have time for and that they function optimally with minimal sleep. In fact there is even a  “sleepless elite,” like Barack Obama, Dean Karnazes, Martha Stewart, and Marissa Mayer. Who claim to sleep only four or five hours a night. However, I would argue 99.99 percent of the time, they are lying to themselves. They are instead functioning at a suboptimal level and the cost of this is their health. Sure there is variance in optimal amount of sleep needed from person to person, but it is by no means this drastic.

The average night’s sleep today equates to approximately 6.9 hrs whereas in 1910 the average was 9 hrs! That is a substantial decline in a short period of time and we are paying for it!

Close to home in Australia a study published in March this year calculated the financial and nonfinancial costs associated with inadequate sleep for the year of  2016–2017 (US dollars). “The estimated total financial cost of $17.88 billion represents 1.55% of Australian gross domestic product. The estimated nonfinancial cost of $27.33 billion represents 4.6% of the total Australian burden of disease for the year.”

Chernobyl

If you cast your mind back to the disaster at: Three Mile Island, Chernobyl, The gas leak at Bhopal, The Zeebrugge ferry accident, The Exxon Valdez oil spill. When you do a little research, you’ll find that these and many other major industrial disasters have been directly linked to sleep deprivation. Therefore, the financial cost associated with lack of sleep has great potential to be significantly higher.

With the ‘24/7’ society there is no ‘off’ switch and with the increasing night time use of TV, internet and mobile phones this means adequate amounts of uninterrupted sleep is becoming increasingly compromised. With this paradigm shift to 24/7 society, we have more shift workers who are required to service the needs of our society. I am sure everyone knows someone that works night shift. This roster exposes them to significant circadian disruption which is likely to add to the growing financial cost of sleep deprivation seen at the workplace. Quite a scary thing to think about when a lot of the shift workers are those that work in healthcare. To put this in perspective 100,000 deaths occur each year in US hospitals due to medical errors and sleep deprivation.

 

University student sleeping in lecture hall

Sleep loss is happening across the population spectrum from children, students to adults. We are all affected. The table below from a 2004 study in America highlights children of various age groups and clearly identifies their lack of sleep, with many not even achieving the desired number of sleep hours. A study done with Auckland University students in New Zealand showed that a large number (39.4%) of university students where suffering from significant sleep deprivation symptoms. What was interesting and shocking from this study was that students were presenting with clinically significant levels of depression (~17.3% of students) and anxiety (~19.7% of students).

Sleep across a 24hr period (2004 America Study): 

Age Group Suggested (hrs) Average sleep (hrs)
Infants 14-15 12.7
Toddlers 12-14 11.7
Preschool 11-13 10.4
School aged Children 10-11 9.5

(Note: All sleep times are averages.)

 

Summary 

Hopefully this has started to highlight to you the impact of sleep and its importance. As I mentioned at the beginning, sleep underpins everything and if you are lacking in that department you are functioning at a suboptimal level and accelerating the aging process.

Stay tuned for the rest of the month of August as we provide you with the tricks and tools to hack your sleep and get you back to performing at your best.

 

References:

Adams, R., Appleton, S., Taylor, A., & Antic, N. (2016). Report to the Sleep Health Foundation 2016 Sleep Health Survey of Australian Adults The Adelaide Institute for Sleep Health.

Aurora, R. N., Collop, N. A., Jacobowitz, O., Thomas, S. M., Quan, S. F., & Aronsky, A. J. (2015). Quality Measures for the Care of Adult Patients with, 11(3).

Ferrie, J. E., Kumari, M., Salo, P., Singh-manoux, A., & Kivima, M. (2018). Sleep epidemiology — a rapidly growing field, (October 2011), 1431–1437. https://doi.org/10.1093/ije/dyr203

Hillman, D., Mitchell, S., Streatfeild, J., Burns, C., Bruck, D., & Pezzullo, L. (2018). The economic cost of inadequate sleep, (July), 1–13. https://doi.org/10.1093/sleep/zsy083

Report, M. W. (2011). National Sleep Awareness Week Unhealthy Sleep-Related Behaviors, 60(8), 2005–2008.

Samaranayake, C. B., Arroll, B., & Fernando, A. T. (2014). THE NEW ZEALAND, 127(1399), 13–22.

Smaldone, A., Honig, J. C., & Byrne, M. W. (2007). Sleepless in America : Inadequate Sleep and Relationships to Health and Well-being of Our Nation ’ s Children, 119(February), 29–37. https://doi.org/10.1542/peds.2006-2089F