Sleep is one of the most enjoyable behavioral habits that millions of years of evolution has conferred upon us. It is a complex interplay of biological processes including a motley crew of characters – from hormones, neurotransmitters, biological cycles to brain waves that produces a state of unconsciousness. Without getting too technical, let’s say that it’s one of the 3 pillars of health with diet, and exercise. It is the time when the body and the brain rests after a hard day’s work, repairing wear and tear to the body, clearing the brain of the toxic chemicals, consolidating our memory, building new skills and taking us on our own metaverse adventure in black and white (in rare occasions in color) i.e. our dreams.
Throughout the ages, the intricate workings of sleep, which makes up 36% (one third )of our lives, has eluded researchers as there was no way to study the brain and the reason why so little has been written about it. We have been conjecturing about the purported reason for sleep for millennia, though. From being a healing method and a God (ancient Greece), a place for divine messages and prophecies (ancient Egypt), maintaining harmony and balance (ancient China) to being a reservoir of power, mystery and restoration (ancient India), there have been as many explanations for sleep as there have been cultures. But it was not until the 1950s that sleep research became a research area in itself and threw light on the reason and the mechanism of sleep (we will talk more about it in a separate blog).
Contrary to popular belief, sleep is not a period of brain inactivity. There are distinctive changes that happen in your brain as you cycle from wakefulness to non-REM (rapid eye movement) sleep (decrease in activation of neurons) and from non-REM to REM sleep (very similar neural activity to the wakefulness state of the brain). Other remarkable biological feats during sleep include thermoregulation (temperature falls by 1-2 degrees and normalizes as we wake up), breathing rate (falls during non-REM sleep), blood pressure (‘dips’ by 10-20% thus protecting cardiovascular health), the growth hormone levels increase during sleep (one of the reasons why infants and kids sleep more), the thyroid stimulating hormones (TSH), cortisol, vasopressin, prolactin and many more hormone levels change during sleep (the topic of hormones will be covered in separate blog posts).
These programmed biological changes during sleep have a multitude of benefits for our systems. There is no system that is not positively affected by sleep and hence the lack of it proves detrimental to our physical and mental health. Sleep deprivation and sleep disorders (of which there are around 100) not only negatively impact our physical health including our cardiovascular system (precipitating factor for blood pressure, heart diseases etc), metabolic system (Type 2 diabetes), Immune system (lower natural defenses against infections), Nervous system (higher pain sensitivity, low fidelity decision making etc) but also impacts our mental health which makes us prone to stress, depression, lower emotional regulation and mood swings to name just a few.
While sleep deprivation is when you cannot get enough sleep (usually between 7 and 9 hours), sleep disorders are more insidious and are usually marked by an underlying condition, be it stress, mental illnesses or physical illnesses (chronic pain etc). According to various research reports, the prevalence of sleep disorder globally is between 20% – 41.7% (Recovery Village) and about 30% of Indians suffer from the most common sleep disorder, Insomnia (thehealthsite.com). Sleep disorders are commonly under-reported across the globe, because many of the changes in sleep are attributed to “normal aging”, or the wide belief that sleep issues affect just that-your sleep. Sleep deprivation has far reaching consequences; and with time, researchers are uncoding the multiple adverse effects of this phenomenon on our body and mind.
In this blog, we will talk about the science and art of sleep and sleep disorders. Along the way, we will meet many heroes and villains, unpack the latest science, demystify some of the common misconceptions about sleep and in doing so assign sleep its rightful place and develop an appreciation for it. Let’s reunite with sleep again.
References:
The forgotten medieval habit of ‘two sleeps’ (BBC)
Science of Sleep: What is Sleep? (Harvard Medical School)
Schulz H. The history of sleep research and sleep medicine in Europe. J Sleep Res. 2022 Aug;31(4):e13602. doi: 10.1111/jsr.13602. Epub 2022 May 6. PMID: 35522132.