The rhythms of life are etched into the molecular chemistry of our bodies reflecting the night/day, dark/light cycles of galactic patterns in our solar system. Life on earth depends upon the circular orbit, the tilt of the moon, our gravity inducing molten core, Saturn and Jupiter’s asteroid absorbing presence, and many other interdependent factors that interface in precise and mutually stabilizing patterns of behavior. There is also a natural somatic rhythmicity that synchronizes life functions including: sleep/wake, movement/rest, internal body temperature, feeding, excretion, the rise and fall of hormones and neurohormones. Daytime activity and light promote movement and cognition that utilize energy stores that are replenished at night. Peaceful feet on the ground living, involves universal rules that demand balance and synchronicity within our life environment.
A cluster of brain neurons on each side of our optic nerves is referred to as the master circadian switch. It is here that signals of light/dark, cold/warm are garnered from our sensory cells , particularly our eyes, entraining genetically programmed rhythms of wake/sleep with our day/night experience. This master circadian switch registers environmental changes in light/dark, and temperature and in response it establishes the cyclical temporal architecture of the body from cell, to tissue, to system, to behavior.
There are multifaceted awake systems and sleep systems that interface and cycle one to the other. There are activating neurotransmitters that are elevated and dominate during waking. Each does something different, but like an orchestra they are in balance and accord with one another. Orexin is a primary neurochemical promoting wakefulness. It stimulates the other activating neurotransmitters systems, including histamine (remember antihistamines make you sleepy), and the very important monoamines. Cortisol, your primary stress hormone, is another critical player in the awake body. Cortisol levels peak in the morning and fall to sometimes imperceptible levels in the evening, slowly rising and reaching its apogee again the following morning. It acts as a messenger helping to coordinate the clock systems in our cells, tissues, and body with the master circadian switch that is registering changes in our outside world.
Sleeping and waking represent a continuum. They are the yin and yang of each other. Balance and progression seem to be key in understanding these states of living. It is not likely that a stressed, agitated day will lead to a restful night. Having a peaceful, productive, active, and light filled day will greatly increase the chance of restful and restorative sleep. Activity and daylight are intimately tied to good sleep. Waking performance depends upon the cycling sleep/wake system which is regulated by two primary driving forces: the homeostatic pressure of active time awake and circadian light/dark experience. The brain is particularly sensitive to sleep energy restoration need. Unlike other body systems, the brain only uses carbohydrates as energy. Its energy resources are in the blood circulation and a small supply that is stored in the glia support cells. The electroencephalogram (EEG), a graph representing the cyclic stages of electrical brain activity, indicates that the incidence of slow waves on a sleep EEG graph is clearly related to the previous time awake reflecting the expenditure of energy during daytime activity and the related homeostatic need for sleep restoration. As we are cognitively and physically active, cells discharge in our bodies. As cellular energy stores are used during daytime activity, a chemical metabolite called adenosine builds up, and, along with circadian light/dark experience, promotes sleep at night.
The detachment between our routine patterns of living and our earth’s day/night cycle can disrupt the intricate synchrony of external and genetically driven internal rhythms that promote balanced body chemistry, restful sleep, energy restoration, and a Goldilocks feeling day. Caffeine is an adenosine antagonist. Too much caffeine can interfere with the natural build of of homeostatic sleep pressure. It is disturbing that the daily routines of many workers, including health professionals, necessitate spending days in buildings without windows, sometimes in job positions with very little movement. Remember that most of mankind has lived as foragers, walking, gathering and hunting outside. Their movement and sleep were dictated to a great extent by the day/night cycles in our earth. There are many good aspects of our technologically developed civilization, but it is clear that it may take a more complex effort to synchronize daily life habits with our outside environment.
Light and darkness are profoundly tied to a balanced cycle of living and well being. We sleep better during the night if we have had bright light during the day. Our brain tends to be more activated in bright light, even artificial light. Light impacts cognition and endocrine systems. Artificial light at night has vastly increased across the world. We have only to google a night time earth map view to see how expansive it has become. Nearly half of our genes are turned on and off through circadian signals related to our master clock system registering the light/dark experience in our environment.
Melatonin rises in the dark and falls during the day. Melatonin decreases body temperature which is an important factor in sleep promotion. It cools the sleeping body, and its decline in the day increases the temperature in the awake body. Chronically high nighttime body temperature may increase the incidence of insomnia and the frequency of headaches, while sleep deprivation lowers daytime body temperature. Melatonin is high in hibernating animals, and also decreases estrogen and testosterone. Alcohol decreases melatonin. Melatonin can also be negatively impacted by just 5 or six flashes of blue light-our cell phones, i-pads, and computers. The blue light can delay the onset of melatonin in the evening, leaving us awake until later. Flashes of bright/blue light can even decrease melatonin dramatically throughout the night, interrupting the important body sleep/wake synchrony with night/day cycles of dark and light.
The Restorative Synchrony of Sleep
Sleep study EEG graphs reflect a harmonic progression of events happening in the sleeping body at night, including brain waves that appear to represent the revitalizing processes of different body/brain systems. The graph depicts the rhythmic interface of body and brain systems in clearly delineated patterns and cycles. The complexity of energy restoration and body repair in sleep is astonishing. The 2 main stages of sleep cycles alternate at about 90-minute intervals. Non-rapid eye movement (NREM) sleep tends to dominate early night sleep and reflects remarkably decreased brain and body activity, but the body can move. Rapid eye movement (REM) sleep progressively increases though out the night and reflects a seemingly awake brain in a paralyzed body.
A recent bevy of interest has been focused on one small cyclic portion of the sleep state graph, periodic episodes of “spindles” occurring early in the night’s sleep (seen on an EEG computer graph as elevations in a slow waves). Spindles seem to appear in coordination with other slight elevations on the sleep graphs (referred to as K-complexes). These are related to maintaining sleep by preventing sensory information in the sleeping environment to reach consciousness, unless it is very strong or threatening. These graph elevations seem to also personify neuronal mechanisms that allow a window of awareness during sleep to monitor threat.
Spindles originate in the thalamus, a part of the brain that is a bit of a way station directing and coordinating information and function. Spindles may reflect the thalamus telling the cortex to stay off line during sleep. The signal is sent from the thalamus to the hippocampus, the short term memory holder for the day’s events, which seems to be in dialogue with the cortex, and there important information is sorted out for storage in existing memory centers while erasing memory representations of irrelevant events. Spindle episodes may also appertain to the brain’s efforts to assimilate traumatic information that may resist integration into complex memory.
In addition, sleep graph spindles are related to the brains ability to sustain attention, and its capacity to block irrelevant sensory information while focusing on what is important for optimal adaptation. We know that schizophrenic patients have very few spindles. This decrease in the spindle related restorative brain activity of schizophrenic patients is not linked to medication but to the neurodegenerative components of the disease. People with untreated sleep apnea also have less spindle activity and have been shown to have poorer motor learning. Spindles are just one small but complex piece of the sleep graph’s representation of the cyclic intricacies of the nighttime restoration of sleeping brain and body.
Non-REM/REM, Rhythmic Succession
REM or dream sleep increases later in the night, reaching a crescendo during the final stage of a 7 or 8 hour night. It is thought to be a period of intense memory consolidation, coding the new information from the previous day into existing memory. The integration of new knowledge seems to strive for emotional stability. Interestingly oxytocin, our body’s primary bonding hormone, increases in REM sleep. Some researchers suggest that this rise may be related to social/attachment dream content. Less REM sleep is associated with poor decision making and more risk taking.The sleep graph during REM sleep resembles brain wave activity in an awake state. However, input from the external world is blocked and movement associated with the waking brain is completely stopped. As mentioned earlier, the body is paralyzed in REM sleep. All of the activating chemicals, monoamines in particular, are greatly decreased during all sleep phases. However, the activating chemical acetylcholine which seems to be the primary chemical mechanism for the observed brain arousal during REM sleep.
Synchronistic Life Patterns
The daily rhythms of living greatly impact sleep, daytime energy, and health. Circadian sleep disruption is associated with many medical and psychiatric disorders. Our brain is encapsulated within our bodies. A healthy body most often reflects a healthy brain. Dysregulation in the sleep/wake circadian system causes weight gain, even if a regular diet is maintained. People who exercise in a regular and balanced manner, for instance walking an hour a day, tend to live longer than those who exercise routinely but in extreme. Genetics seem to also be a factor in how long, at what time and how well we sleep. Early birds and larks have a genetic/environment component, but that of course is entrained by day and night routines of activity and rest.
Too much sleep or too little sleep increases mortality. It seems that 7 or 8 hours is a more balanced amount. Sleep deprivation costs many systems and decreases lifetime health. All of the cells of our body systems are replenished and repaired in sleep, including our bones, skin, blood, and brain. Consistent sleep loss decreases health in many areas. The incidence of heart attack and dementia surge for untreated sleep apnea. Indeed, sleep makes us smarter as the systems of the brain are restored and readied for the next day’s activity. Memory is consolidated in sleep. It also decreases toxins in the brain. Estrogen seems to help insomnia in premenopausal women, and menopause increases the incidence of apnea in women so that the rates approach that of men. Hypothyroidism heightens the occurrence of apnea, and REM sleep disorder seems to be a harbinger of Parkinson’s disease.
Many substances and illnesses may impact the symmetry of sleep and waking states including: alcohol, caffeine , corticosteroids, decongestants, Statins, stimulants, untreated sleep apnea, neurodegenerative disease, antidepressants, sleeping medications and sedatives. Studies of chronic cannabis (marijuana) users indicate that it inevitably disrupts sleep and promotes depression. Chronic marijuana users exhibit cognitive decline over time, and marijuana withdrawal includes increased sleep difficulties, nightmares, aggression, irritability, and decreased appetite. Recent studies indicate that there is an increase in mortality with the long term use of Ambien type drugs. About the same time earlier this year a strong long term study of benzodiazepines, Valium, Ativan, Klonopin type drugs has been show in increase the prevalence of dementia. These medications are quickly habituating and must be titrated slowly as we teach the body to return to cycles of waking and sleeping that are synchronized with our world environment, moving and resting, eating and sleeping in accord with the daily earth patterns of light and dark .
Life habits of wakefulness and sleep are symphonic players in a concert of health and wellbeing promoting beautiful life motifs or discordant cacophony.
- Dr. Linda Klaitz, Medical Psychologist