Sleeping is one of the key pillars of “health”, alongside a healthy gut, emotional & mental wellbeing, and consistent body movement (not necessarily in that order!). Quick food for thought: our ancestors would have evolved away from the need to catch some zzz’s if sleep were not absolutely key in our survival and circadian rhythm.
What is "circadian rhythm"?
It’s the internal perception of the daily cycle of light and dark based on retinal (eye) activity related to sunlight. Though much easier said than done, we should be mindful of keeping a consistent and (adequate) daily slumber routine to ensure quality sleep. We can measure the “quality” of sleep using two parameters:
- The physical & mental restoration that takes place during sleep
- The types of and cadence of different brain waves that take place during sleep
# 1: PHYSICAL & MENTAL RESTORATION DURING SLEEP
Studies of sleep and sleep deprivation suggest that the functions of sleep include (source):
- recovery at the cellular, network, and hormone system level
- energy conservation and ability to adapt to surrounding environments
- learning and brain plasticity (i.e.: your ability to constantly shift, grow, and reorganize both behaviors and thoughts).
Studies have indicated that changes in mood may be due in part to the effects of sleep deprivation on the processing of emotional memory. In other words, our tendency to select and remember negative memories after inadequate sleep (source).
FUN FACT: R.E.M. vs. Non-R.E.M. Sleep
You've also probably heard of REM (rapid eye movement) and NON REM (non rapid eye movement) sleep periods. Fun facts about
NON REM: typically experience these in the earlier hours of the night, (e.g., 11 p.m. – 3 a.m.). Fun facts about REM: it covers the 5th and final stage of a 90-minute sleep cycle, it's when most dreaming occurs and while our eyes are darting back and forth during REM, the muscles that move our bodies are paralyzed 😳 🤯 (NOTE: other vital muscles, such as our heart and diaphragm, continue to function normally).
#2: TYPES & CADENCE OF DIFFERENT BRAIN WAVES
There are five types of brain waves: Gamma, Beta, Alpha, Theta, and Delta. Yes, basically a group of sororities from college 😅 A sleep cycle lasts about 90 minutes and during that 90 minutes, we run through 3 of the 5 cycles of sleep! Quick note: The need for sleep continues to increase as you move backward towards infancy (i.e.: needed in greater quantities for infants, needed in smaller quantities as we age). Gamma and beta brain waves indicate full alertness and are not involved in the five sleep cycles. Alpha, theta and delta however alternate in different combinations throughout the five stages of sleep!
- Stage 1 of sleep: Non-REM, Alpha & Theta waves
- Stage 2 of sleep: Non-REM, Theta waves + Sleep Spindles (which are short bursts of activity that are thought to work on cementing learning and memory)
- Stage 3 & 4 of sleep: Non-REM, Delta waves
- Stage 5 of sleep: REM, the brain waves associated with this stage of sleep are very similar to those observed when a person is awake (as shown in the bottom picture)
FUN FACT: STAGE 1 SLEEP
People often report that they have not been asleep if they are awoken during stage 1 sleep (source).
Several studies have shown that after several nights of inadequate sleep, levels of the satiety hormone peptide YY are lower and levels of the hunger hormone ghrelin are higher in participants (Hibi et al., 2017; Reutrakul & Van Cauter, 2018).
