Vol. 3 Sleep: The beloved… or not so beloved habit
✅ Get some sleep… sleep cures everything! An old classic piece of folk wisdom!
❌ Others, of course, prefer short sleep because… one day we’ll sleep for good anyway.
🧐 Let’s go learn some basic things about sleep together and summarize a few facts.
😴🌃🛌 Sleep is defined as a rapidly reversible physiological state of reduced alertness, mobility and metabolism. It is observed in all animals, indicating very deep roots in the evolutionary chain. The human body spends roughly 1/3 of life in a state of sleep.
🧑💼🔬 Sleep is broadly classified as REM (rapid eye movement) and non-REM based on findings from three tests: electroencephalography, electromyography, and electrooculography. Non-REM sleep is further divided into three stages: N1, N2, and N3. Correspondingly, REM sleep (also referred to as stage R of sleep) has two phases: the phasic and the tonic.
📙💬 Stage N1 is usually the first during the transition into sleep, corresponds to the lightest sleep, and is brief. In contrast, stage N2 is the longest in duration. Stage N3 is referred to as deep sleep. REM sleep is associated with an increased presence of dreams. Phasic REM is characterized by intense eye movements, while intervals of tonic REM are observed between the phasic episodes.
👷👨👩👧👦📅 Sleep architecture changes throughout life in terms of total duration, the duration of each stage, and the sequence of the stages. Typically, an adult entering sleep goes successively through stages N1, N2, N3, and REM. This sequence is usually repeated in 4–5 cycles. Each cycle is characterized by different durations of each stage.
⁉️ But why do we sleep? What is truly the role of this phenomenon?
👀🧠🛠 We still do not have clear answers. It is documented that sleep exerts rejuvenating effects on the entire body—something like daily maintenance. It also appears that during sleep the body clears unnecessary substances, promoting optimal function of hormones and the Central Nervous System. This may be the reason why nighttime sleep seems more beneficial than sleep during other times of the day. For more information, you can read about the Circadian Rhythm. Finally, sleep may play a decisive role in shaping and remodeling the brain at a microscopic level. Therefore, it affects memory and various cognitive functions.
😵💫🧑🏫📃 Last but not least, here is a short summary of sleep disorders. We could classify them into seven major categories:
1)Insomnias.
2)Breathing-related disorders, with the most characteristic example being obstructive sleep apnea syndrome, which predisposes, among other things, to the development of Arterial Hypertension.
3)Hypersomnias, such as narcolepsy (no… it’s not what most people think).
4)Circadian Rhythm Disorders.
5)Parasomnias, such as sleepwalking.
6)Movement disorders, such as restless legs syndrome.
7)Other unclassified disorders, such as those with atypical or multiple characteristics from the previous six.
🙌😇😎 Intentionally, we will not comment on the hottest question… “Doctor, how many hours should I ideally sleep?” — so we can spark a bit of curiosity for further personal research!
📑 References
-Siegel JM. Sleep viewed as a state of adaptive inactivity. Nat Rev Neurosci. 2009 Oct;10(10):747-53. doi: 10.1038/nrn2697. Epub 2009 Aug 5. PMID: 19654581; PMCID: PMC8740608.
-Ohayon MM, Carskadon MA, Guilleminault C, Vitiello MV. Meta-analysis of quantitative sleep parameters from childhood to old age in healthy individuals: developing normative sleep values across the human lifespan. Sleep. 2004 Nov 1;27(7):1255-73. doi: 10.1093/sleep/27.7.1255. PMID: 15586779.
-Sateia MJ. International classification of sleep disorders-third edition: highlights and modifications. Chest. 2014 Nov;146(5):1387-1394. doi: 10.1378/chest.14-0970. PMID: 25367475.