This touches on some of the key questions around sleep. What is it? how much do I need? What are the benefits of good sleep hygiene. Join us as we delve into the key concepts of health.
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In this blog, we will explore the realm of sleep and the well-documented advantages it offers. It's essential to emphasize that humans possess remarkable adaptability and resilience. Experiencing one or a few nights of subpar sleep is a common occurrence. The following blog post provides an interpretation of the existing body of sleep literature, bearing in mind that updates to this literature are occurring with increasing frequency.
"If the benefits of sleep were in a pill, everyone would want it!"
Sleep has been present in medical and academic circles on PubMed since before 1810, with the term 'sleep hygiene' (defined as processes and habits that improve and encourage sleeping) introduced in 1948. Since then, the research into sleep has continued with the benefits of good sleep yielding improvement in metabolic immune reactions [1], mental health [2] and cognition (learning) [3]. A lack of sleep is also associated with multiple adverse health conditions, including psychiatric and major inflammatory disorders to the cardiovascular and neurological systems [4]. Further, good quality and quantity of sleep (i.e., More than 7 hours, but less than 8 hours) is linked to a strong reduction for all cause mortality [5].
This blog will discuss the benefits of sleep and how the combat sports athlete can use this recovery superpower to better their sport participation.
Sleep in humans is a subconscious process where an autonomic deep rest-state occurs. In combat sports, a fight draws the most processes from your sympathetic (fight or flight) brain circuits with sleep drawing most of its processing from the restorative parasympathetic (rest and digest) brain circuits [6]. This balance is crucial in general, but especially for 'fight or flight' based athletes in the combat sports.
Sleep is broken down into Rapid Eye Movement (REM) and non-Rapid Eye Movement (NREM) sleep types [7]. These two distinct forms of sleep are required in different ratios for cardiovascular recovery and cognitive and emotional consolidation. These sleep types are separated into two halves (1st half and 2nd half of the 8 hour sleep cycle), with each half forming the two-process model of sleep that was developed in 1979 after first being observed in rats by Borbely et al [8]. These two parts of sleep require different ratios of REM and NREM and are linked to different benefits. The first 4-hour sleep period is linked with cardiovascular health with disruption to this period of sleep results in increased blood pressure and heart rate [9]. This is thought to be connected to a disruption to the central nervous system (CNS) where an increase in sympathetic tone (or fight and flight neural activity) reduces the depth (or stage) of the parasympathetic (rest and digest) period of sleep [11].
In this state of parasympathetic rest, the nerve cells in the brain flow from an on and off state in specific rhythms that emulate mathematical waves. These waves in sleep are identified as Alpha, Beta and Delta waves, with each stage of sleep representing more inhibited (or deeper) thalamocortical activity. The final 4-hour sleep period houses the most REM (rapid eye movement) sleep minutes [8]. REM sleep is an active portion of sleep where under functional MRI the brain activity of REM is similar to the brain activity of the waking period [12]. There is no specific sleep wave for the REM period. During REM sleep dreams are constructed by the brain and is thought be responsible for daily emotional memory consolidation that is required in healthy adult life [12]. Lacking the 2nd half of the sleeping process will render you more irritable whilst impeding emotional memory and processing [8].
In short, we think yes but maybe no.
There are many genes in the human genome that impact sleep. These genes can be subdivided into genes that influence either the NREM or REM sleep stages with specific influence to the distinct REM and NREM sleep neural circuit. In both cases these genes affect the sleep duration (how long), sleep stability (how well) and circadian timing (when).
When looking at these genes, there is some evidence in animal studies (mice) that some subjects are more resilient to the negative effects of sleep deprivation. This suggests the hypothesis that these subjects are more efficient at sleeping. To identify a few, some genetic differences occur in the genetic expression of the ADRB1 and NPSR1 in the human genome [13]. In these subjects a deeper delta wave power during NREM sleep, i.e., sleep that is deeper or with more pressure [14]. These genes whilst making sleep deeper also relieves this pressure quicker to the lighter stages of sleep once the sleep stage quotas are met.
The REM sleep state fluctuates over the human lifetime with key development benefits early in human life [12]. In the infancy years REM sleep is thought to be linked with brain development, learning and sensorimotor integration. Infants develop their capacity for REM sleep in parallel to cortical brain (big brain) development with the most active REM sleep occurring during the teenage years [15]. Later in life, REM sleep encourages the consolidation of spatial location (whereabouts) and integrates daily emotional memory. As humans age, the total duration of REM sleep lessens with some REM periods of sleep replaced by periods of wakefulness [16]. This peaks > 65 years of age as compared to young adults and children [16].
In summary, we know we need the two different sleep types at different ratio's throughout life. When we don't get enough of each type of sleep we know the detrimental affects that they can cause. When we get too much sleep or hypersomnia (also known as over-sleeping) the negative affects in adolescent children are similar to the detrimental affects of too little sleep. The take-away message is; 8 hours of sleep should be the goal.
Sleep is anti-inflammatory, with adequate sleep improving recovery for all individuals.
Sleep is known to reduce metabolic demand of the body by assuming a deep parasympathetic rest and digest state [8]. In this state, recovery processes in the body become more effective and efficient by refolding proteins, improving glucose metabolism (for cellular energy), programmed cell death (apoptosis) [1].
There is a link between higher sleep scores and lower levels of serum (general) inflammation [17, 18]. In combat sports, the management of concussion, whip-lash and neurological over-training should all have sleep hygiene principles as a staple in the recovery phase. We know that regular and good sleep benefits the affected athlete when sleep returns to normal.
Concussion and head impact wise, a key protein used to identify head impact accumulation that is pivotal in the neurodegeneration processes is the 'Tau Protein'. Tau proteins are proteins that primarily exists within the 'grey matta' cells of the brain and provides cellular structure (think of it like as the walls, floors and roofs of a building, with the white cells as the computers and electrical cables in the building) [17]. Tau proteins are released to the surrounding environment outside of the cell (or extra-cellularly) as a normal occurrence that occurs with neural activity (i.e., the more active the nerves are the more normal tau protein is pushed outside of the cell ). It is thought that periods of prolonged neural activity increases the 'pushing' of this process, increasing the likelihood of pathology through this tau protein movement [18]. This tau protein accumulates in the CSF (cerebrospinal fluid), a nutritional fluid that supplies the grey and white 'matta' of the brain and spinal cord. To date, no clear explanation for this normal tau protein migration has been identified, but it is in the extra-cellar migration the tau protein can miss-fold. When this misfolded protein re-enters the cell it causes the in tau-protein in the cell to misfold.
Interestingly, in many recent studies sleep has been seen as an emerging counter to this neuro-inflammatory protein accumulation. This results in the hypothesised prevention of Alzheimer's as the most researched disease type of neurodegeneration. In 2020 Benedict et al, observed the impact a lack of sleep has on the percentage of plasma tau protein [18]. In these young male subjects normal sleep tests identified about 2% of tau protein in their plasma, after a week of sleep deprivation the same members increased the plasma count of tau protein by 15% to 17%. This 15% jump is significant and worthy of future investigation. At this stage, albeit preliminary, it is hypothesised that the cleaning and to some capacity the refolding of these proteins occur in the sleep cycle, with deep parasympathetic sleep improving this refolding rate of the tau-proteins.
Some questions still remain here, as the direction of this relationship is not clear. The science community are unsure if people with a lot of inflammation are kept awake or if a sleep deprivation is pro-inflammatory. That is, does a lack of sleep cause inflammation build-up or does inflammation build up hinder sleep?
In summary, sleep is anti-inflammatory and is linked to specific anti-neurodegeneration through reducing tau protein migration and improving tau protein folding's. Combat athletes may not be damaging brain tissue with sport participation, but the chronic and sustained bouts of poor sleep due to poor sleep-hygiene may be having the driving force behind certain post combat sports participation outcomes.
The process of falling asleep is separate to staying asleep. A way to enhance this process is through achieving a sleep state.
Some tips to achieve this are as follow:
> Maintain a sleep schedule where you wake up and fall asleep at a similar time daily
> Exercise in the morning or 3+ hours before sleep
> Eat 2+ hours before bed
> Reduce light stimulation before bed
> Set room temperature to 20.5 degrees Celsius (2 degrees warmer than sleeping core temperature)
> Observe the sunrise and sunset light rays during the day
If you have any illnesses resulting in poor sleeping, ensure they are being addressed by expert persons. Irregularities sleeping caused by fever, viral infection etc can also result in sleep difficulties. These causes require a different course of treatment.
1. Besedovsky L, Lange T, Haack M. The sleep-immune crosstalk in health and disease. Physiological reviews. 2019 Mar.
2. Freeman D, Sheaves B, Goodwin GM, Yu LM, Nickless A, Harrison PJ, Emsley R, Luik AI, Foster RG, Wadekar V, Hinds C. The effects of improving sleep on mental health (OASIS): a randomised controlled trial with mediation analysis. The Lancet Psychiatry. 2017 Oct.
3. Mason GM, Lokhandwala S, Riggins T, Spencer RM. Sleep and human cognitive development. Sleep Medicine Reviews. 2021 Jun1.
4. Irwin MR, Olmstead R, Carroll JE. Sleep disturbance, sleep duration, and inflammation: a systematic review and meta-analysis of cohort studies and experimental sleep deprivation. Biological psychiatry. 2016 Jul.
5. Cappuccio FP, D'Elia L, Strazzullo P, Miller MA. Sleep duration and all-cause mortality: a systematic review and meta-analysis of prospective studies. Sleep. 2010 May.
6. VaroneckasG, Plauška K, Kauk J. Components of the heart rhythm power spectrum in wakefulness and individual sleep stages. International journal of psychophysiology. 1986 Jul.
7. Chen KS, Xu M, Zhang Z, Chang WC, Gaj T,Schaffer DV, Dan Y. A hypothalamic switch for REM and non-REM sleep. Neuron.2018 Mar.
8. Borbély A. The two‐process model of sleep regulation: Beginnings and outlook. Journal of Sleep Research. 2022 May.
9. Grandner MA, Alfonso-Miller P, Fernandez-Mendoza J,Shetty S, Shenoy S, Combs D. Sleep: important considerations for the prevention of cardiovascular disease. Current Opinion in Cardiology. 2016 Sep.
10. LusardiP, Zoppi A, Preti P, Pesce RM, Piazza E, Fogari R. Effects of insufficient sleep on blood pressure in hypertensive patients: a 24-h study. American journal of hypertension. 1999 Jan.
11. Carey RM, Calhoun DA, Bakris GL, Brook RD, Daugherty SL, Dennison-Himmelfarb CR, Egan BM, Flack JM, Gidding SS, Judd E, Lackland DT. Resistant hypertension: detection, evaluation, and management: a scientific statement from the American Heart Association. Hypertension. 2018 Nov.
12. Blumberg MS, Lesku JA, Libourel PA, Schmidt MH, Rattenborg NC. What is REM sleep?. Current biology. 2020 Jan.
13. Shi G, Yin C, Fan Z, Xing L, Mostovoy Y, Kwok PY, AshbrookLH, Krystal AD, Ptáček LJ, Fu YH. Mutations in metabotropic glutamate receptor1 contribute to natural short sleep trait. Current Biology. 2021 Jan.
14. Shi G, Xing L,Wu D, Bhattacharyya BJ, Jones CR, McMahon T, Chong SC, Chen JA, Coppola G, Geschwind D, Krystal A. A rare mutation of β1-adrenergic receptor affects sleep/wake behaviors. Neuron. 2019 Sep.
15. Knoop MS, de Groot ER, Dudink J. Current ideas about the roles of rapid eye movement and non–rapid eye movement sleep in brain development. Acta Paediatrica. 2021 Jan.
16. Tatineny P, Shafi F, Gohar A, Bhat A. Sleep in the elderly. Missouri Medicine. 2020 Sep.
17. Holth JK, Fritschi SK, Wang C, Pedersen NP, Cirrito JR, Mahan TE, Finn MB, Manis M, Geerling JC, Fuller PM, Lucey BP. The sleep-wake cycle regulates brain interstitial fluid tau in mice and CSF tau in humans. Science. 2019 Feb 22;363(6429):880-4.
18. Benedict C, Blennow K, Zetterberg H, Cedernaes J. Effects of acute sleep loss on diurnal plasma dynamics of CNS health biomarkers in young men. Neurology. 2020 Mar17;94(11):e1181-9.
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This blog post will touch on the importance of a strong and adaptable neck and it’s relationship with the eyes. We will round up with some anecdotes from my clinical experiences.
Based in Sydney Australia, my goal is to provide high quality information about boxing injuries, chiropractic, and academia to the boxing and wider sporting communities.
