ABCs of SLEEP || E is for Entrainment

Entrainment is the word scientists use to explain how we all, as human beings, "set our clocks." Our human body clocks, to be specific. Our bodies have multiple "clocks" in specific organs as well as inside each and every blood cell, and like clockwork they help us to manage our daily rhythms, which inform the behaviors that make us functioning human beings.

Think about hunger, sleep, sex, digestion. These are all physiological processes that require some precise timing on the part of our personal clocks. This is what our circadian rhythms are all about. When our rhythms fall out of synchronicity, that is when we can experience disease, general malaise or other kinds of biological confusion. We really can't live healthy lives without adhering to circadian rhythms.

The most obvious way that we entrain ourselves to life's rhythms is through our perception of light. Light is what marks the day/night cycles; the sun rises, the sun sets. Sunlight, and its absence, also helps the body to detect seasonal shifts. These are primal communications we share with the earth. All living things require the light-dark cycles, as established by the rotations of our planet, to manage these critical life rhythms. 

Light is perceived by the eyes, of course, but also through the skin via melanopsin. Signals collected by these organs are sent to the body's main pacemaker, the suprachiasmatic nucleus (SCN), which issues orders to all others parts of the body to function according to a preset pattern of rhythms that, by and large, most human beings are commonly entrained to using light.

For the vast majority of human beings, light is the key influence over when we sleep and when we wake up. For those with circadian rhythm disorders like Non-24 Sleep -Wake Disorder (also known as free-running disorder) or shift work disorder or even a temporary case of jet lag, light doesn't deliver the same influence over sleep-wake cycles. 

The person who suffers from these kinds of disorders struggles to maintain a normal life on an abnormal schedule. They have fallen out of entrainment and need to find a way to "reset" or else they are forced to adjust their schedule in ways that are not typical, even unorthodox, in order to simply get by. 

Imagine the person who can only feel awake and alert in the later afternoon; maybe they have a job working at the toll both during the morning commute. Or imagine the nurse who can only work night shifts but who has children to watch during the day at home. Or the musician who cannot stay awake long enough to attend the gigs he is scheduled to perform at nightclubs. 

Having pattern disruptions in one's rhythms can absolutely devastate the efforts of many to live normally (in this case, meaning "by society's schedule"), and that includes having the ability to earn a living, care for family or function at their maximum potential while on the job. Circadian rhythm disorders also seriously disrupt relationships and social lives.

Non-visual cues

Believe it or not, there are other cues besides light--in science, they call them zeitgebers, which translates as time markers, external or environmental cues that synchronize our biological rhythms--which have a powerful impact on our lives, including our time while sleeping. These are also ways we are entrained to healthy--or unhealthy--rhythms. 

Eating and digesting do not require light or even sight to take place. They require that the gastrointestinal system follow specific cues that dictate that you eat and digest while you are awake. While you sleep, the digestive system goes into sleep mode as well. This is why, generally speaking, most people do not get up in the middle of the night to have a bowel movement. The digestive system does not expect food to enter the alimentary canal at this time. Instead, the act of moving food through the system slows dramatically.

Large meals eaten right before bed, however, can create problems with sleep disruption; the digestive system is suddenly working overtime when it had fully expected to be in bed like the rest of you. Poor sleep can result, as can reflux disease and other health problems related to metabolism. There are lots of studies to suggest that eating out of synch with one's normal body rhythms (meaning, late at night) can lead to imbalanced secretions of certain hormones like melatonin, orexin, leptin and ghrelin, which can impact metabolism in negative ways. 

Finally, there is a circadian shift in metabolism that occurs in the morning as part of your biological rhythms. This is normal; it prompts hunger and stimulates the body to recommence digestion. Now you know why we almost always need to use the restroom first thing in the morning: wakefulness stimulates digestion and the elimination of wastes that have been in your "holding tanks" (meaning, the bladder and the bowel) overnight.

This illustration from the University of Zurich shows how the brain and digestive organs carry their own "pacemakers." The main pacemaker in the body is the suprachiasmatic nucleus (SCN), which is located
deep inside the brain. Its companion pacemakers exist in the digestive system and are driven
by information related to internal cues relayed to them via messages sent by the SCN. 

Activity levels are other non-light time markers that can inform sleep-wake cycles and metabolism. If you exercise too late at night, this could mess with your ability to fall asleep. Physical activity (it could be running a mile or doing laundry) amps up adrenaline and other hormones which encourage wakefulness. 

Similarly, body temperature, which is influenced by how physically active you are, impacts your ability to entrain to patterns that allow for consistent sleep-wake patterns. If you do not get enough physical activity during the day, you may find it hard to fall asleep, as well--with no normal rise and fall in daytime body temperature, the body may not be able to read your activity markers clearly enough to signal sleep to occur. 

Also, the act of sleeping itself is marked by specific patterns of body temperature shifting that prepare the brain and body systems for specific kinds of sleep. If your body temperature is out of whack as you are heading off to bed, you might be missing out on sleep stages that are critical to your body and brain to function at maximum potential.

Temperature-related breaks in entrainment are experienced by people with major stress disorders like PTSD or severe depression: they may generate higher body temperatures at night while in stress response even as they are hoping to fall asleep. Women, because of their monthly cycles, can also experience temporary periods of sleep disruption due to normal alterations in body temperature caused by menstruation or other major changes in hormone balance like pregnancy or menopause.

Alternatives || Sleep Hygiene Tip of the Week: Move, to rest

Image courtesy Etandel.

From the National Sleep Foundation comes this gem:

"People sleep significantly better and feel more alert during the day if they get at least 150 minutes of exercise a week, a new study concludes."

What kind of improvement are they boasting? A 65 percent increase in sleep quality. That's no small thing, given how tired Americans are.

That boils down to 20-25 minutes a day of your favorite exercise, the equivalent of a brisk indoor or outdoor walk daily, or 3 days at the gym or pool or elsewhere for 50 minutes. And it doesn't haven't to include exercise in the formal sense, it could be some heavy lifting out in the yard, or your lunchtime walkabout during the week, or a dip in the pool with your kids on the weekend, or a challenging yoga class, or a night at the community center playing volleyball.

The idea is pretty simple: cardiovascular activity sharpens one's focus, improves daytime productivity and eliminates daytime sleepiness as well as leads to easier sleep onset at night and more restful sleep overall.

Perhaps the best way to look at it is this statement from the NSF: "“Increasingly, the scientific evidence is encouraging as regular physical activity may serve as a non-pharmaceutical alternative to improve sleep.”

If you could replace your sleeping pills with a brisk daily walk to prevent insomnia, wouldn't you?

Some tips for making exercise work for your sleep habits:

1. Reconsider exercise right before bedtime. Exercise releases hormones such as adrenaline (epinephrine) and cortisol, which will lead to extended wakefulness following the workout. Try to put three hours between the end of your workout and bedtime, if you are able.

2. That said, some people can exercise right before bed and not suffer from delayed sleep onset. In fact, this might be the only time some people CAN get their exercise. If you aren't sure how it will affect you, keep a sleep diary that captures how long it takes for you to fall asleep on nights when you've been visited with insomnia. You can also swap muscle-building exercises for high intensity aerobics activities in order to ease into sleep more smoothly.

3. Keep an exercise routine to help establish good sleep patterns overall. Your body likes regularity... in exercise, sleeping, eating... more regularity means less stress.

4. Exercise in the morning outside is the optimal opportunity to not only get your sleep-worthy exercise, but to also re-entrain your brain to daylight, thereby giving your circadian rhythms a boost.

5. Focus on your breathing as you exercise, and try to find a pattern you can stick with comfortably. The respiratory boost of mild exercise can be an excellent way to instill calm in the body afterward.

6. If you shower afterward, try not to use overly hot water if you are heading off to bed. Your body needs a cool down at bedtime if it is going to fall asleep. Keep your shower warm, then follow with a glass of cold water. Sleep in a cool room with layers of blankets you can adjust so as not to be overwarm.

SOURCES

• CNN: Can exercising at night hurt your sleep?
• Mental Health and Physical Activity: Association between objectively-measured physical activity and sleep, NHANES 2005–2006
• National Sleep Foundation: Study: Physical Activity Impacts Overall Quality of Sleep

A friendly reminder that links to websites offering products does not imply endorsement by SleepyHeadCENTRAL.com.

SleepyHeadCENTRAL strongly encourages people with ongoing sleep health problems to approach a medical professional to determine appropriate differential diagnoses and treatment. This post, like all other posts on SHC, is not intended to substitute for medical advice.  

Alternatives: Using sound as a bedtime sendoff

Many people who have trouble sleeping aren't aware of the many options they can try before asking for the over-prescribed (in this writer's opinion) sleeping pill. One of the best solutions for achieving sleep onset and for staying asleep can be found in the use of sound to deliver distraction and relaxation. 

Sleep Music, by A-L-i-E-Nxx

Despite what most people think, the body and brain don't just shut down at night while you are asleep. In fact, your body is always at work somewhere at all times of the day. During sleep, your cells are (ideally) being repaired, your brain is filing away information, your digestive system is working at a different rate based on its own circadian clock, and so forth. Your senses function at varying levels of activity as well.

Visual: Your eyes may be closed, but if there is light in the room, your body still perceives it through photoreceptor cells not only in your eyes, but in your skin.

Taste and smell: Your sense of taste may not be active, but that's because you are not eating. Your sense of smell will slowly shut down, but if someone were to walk into your room with a plate full of freshly cooked bacon while you were in early stages of sleep, you would probably wake up, your mouth would probably water and your digestive system, because of new salivary action, would leap into regular action.

Touch: Your sense of touch will remain somewhat alert. Ideally, you will have a comfortable sleeping environment and not one which keeps you aware of discomfort (poor mattress support, ill-fitting sheets, inappropriate blanket weight, overwarm bed partner, active pets or children in bed, too cool or warm a room, etc.).

Sound is also something the brain processes while you are asleep. This is obvious to people who sleep with snoring bed partners, which could be spouses, children or pets. Noise can pull you out of deeper sleep stages or fragment the stages you are in, which leads to changes in pulse and blood pressure. If you are in the deepest stage of sleep, stage 3 or Delta sleep, you'll be harder to awaken than if you are in early stages of sleep (1 or 2).

In addition, if you are aroused by sound during the night, the way that you deal with it depends a lot on how you regard that sound emotionally. If it's the sound of a door being opened, and you aren't expecting someone to come home in the middle of the night, you will react emotionally with panic or concern. If it's the sound of your cat purring, you'll probably not mind it so much and go back to sleep. If you live in the city but are in a rural environment, you might hear a coyote and the sound of that could increase your stress response and make it harder to fall asleep. Similarly, if you live in the country and hear the same coyote, you'll probably let the sound go in one ear and out the other without much thought. And ruralites, in the city, are infamously known for not being able to sleep against the backdrop of traffic noises outside, while city dwellers can find great comfort in these sounds. Regardless where you live, there will always be the potential for noise pollution from barking dogs, loud parties, construction site racket, crying babies, fog horns, thunderstorms, fireworks, and low-flying jets, as the noise of life happens regardless our best intentions for getting sleep at night.

There are numerous ways to address the control of sound in your sleeping environment as a way to help prevent insomnia or broken sleep across the night.

The most simple way to drown out sound is to block it entirely with earplugs or a noise-canceling headset. This may be all you need, or you might find these items too uncomfortable to wear more than occasionally. Similarly, some people have reported using ski head bands with wide space to cover the ears; they wear the head band over their eyes instead of on the top of their head and keep the ears covered, and this works for them.

If these won't work, then your options generally tend toward the creation of some kind of consistent background noise that masks other smaller household or exterior sounds which might interrupt your sleep.

You may already own a room fan, either on your nightstand, built into the window, on a stand in the corner or overhead. Fans can be useful even in the winter for pushing warm air down by reversing overhead fan blades or by directing conditioned warm air from vents or heaters to the center of the room. They can create just enough background noise to keep the brain from tuning into the tiny sounds of a household, like the refrigerator running or the minor creaks of a house, or of the sound of water in outside gutters.

Soft music is another useful option. You can deliver this in various ways. Tune into a New Age or classical music station on your satellite TV or stereo at a very low volume (but drape a towel over the TV or stereo to block any outgoing light patterns, which can disrupt sleep). Wear noise-canceling headphones or earbuds and listen to very soft, relaxing music from your electronic device (again, turn the device face-down or shut its cover to hide outgoing light patterns). You can use timers to shut off these programs, if available, so that you get just enough soft noise to usher you off to sleep. Avoid listening to spoken word programs, unless they are designed for relaxation, as they tend to command attention and stimulate the brain enough to prevent relaxation.

Sound machines generate different kinds of noise, including white or pink noise, wave sounds, the sounds of storms or rain, and other nature or even manmade sounds (some people like the slow drone of traffic to relax by). They can also generate frequency tones that may help the brain achieve relaxation (see Isochronic tones and binaural beats). If you have a bed partner, you may need to figure out which noise machine sounds work best for the both of you. Interestingly, some people find comfort in the sound of their partner's CPAP machine and are bothered by its absence when their partner is away or not using it.

Isochronic tones and binaural beats are specific kinds of frequencies that may be capable of delivering sleep-friendly tones through a process known as brainwave entrainment. The theory behind brainwave entrainment, generally, is that you can use certain repeated vibrations or frequencies to launch specific kinds of brainwave patterns. Some tones might allow the brain to become more focused (synchronizing with alpha waves), which is desirable for, say, college students, while others could encourage relaxation by creating synchronization with delta wave patterns, which would appeal to insomniacs.

Isochronic tones are defined as specific, carefully spaced pulses of sound that target certain brainwaves that, once processed in the cortex, achieve brainwave entrainment. They are thought by some to be effective without the use of headphones to be heard, unlike binaural beats, which are defined as two slightly different frequencies presented independently to the left and right ear by way of headphones. What the brain “hears” is the subsonic difference between both sounds of a binaural beat, which creates a distinct new "binaural" sound that the brain may then become entrained to.

Theories behind isochronic tones and binaural beats are being researched, but little solid scientific evidence has yet been established to prove their efficacy. However, many people use these particular frequencies in smartphone apps designed to augment meditation and relaxation practices and anecdotally find that these technologies work. While the jury is out, this is still an area of research to watch. It's worth noting that those who suffer from seizures should avoid using these kinds of products until research can prove (or disprove) safe usage for them.

Sound "radio" refers to online radio channels devoted to relaxation music which borrow from theories about brainwave entrainment to offer listeners options for music which can be used for meditation as well as for achieving sleep. They often incorporate isochronic tones or binaural beats. In addition, there are sound relaxation downloads through online media servers like iTunes, and smartphone apps, which can deliver these various options for those who are interested.

Additional resources

The National Sleep Foundation || Listen. Are Noises Keeping You Awake?
Huffington Post || 9 Ways To Block Out Noise And Get A Good Night's Sleep For Once
REDDIT DISCUSSION || The best headphones to SLEEP in? Most comfortable?
Top 10 Reviews || 2015's Best Top Ten Sound Machines
[PRO] Intelegen Inc. || The Science of Audio-Based Binaural Beat Brainwave Entrainment
(supporting brainwave entrainment for sleep)
[CON] Neurologica || Brainwave Entrainment and Marketing Pseudoscience (skeptical about brainwave entrainment for sleep)
Sound Oasis Radio || Listen to 8 Hours of Free White Noise 
Relax Melodies || Free sleep aid application which includes isochronic tones, binaural beats and various white noise options


A friendly reminder that links to websites offering products does not imply endorsement by SleepyHeadCENTRAL.com.

SleepyHeadCENTRAL strongly encourages people with ongoing sleep health problems to approach a medical professional to determine appropriate differential diagnoses and treatment. This post, like all other posts on SHC, is not intended to substitute for medical advice.  

Definitions || What is Normal Sleep?

Happy New Year! I hope that, among your personal resolutions for 2015, you've thought about adding "more and better sleep" to the list. Sleep is not an optional process, after all; you can only replace lost sleep with found sleep. And if you don't, you accrue sleep debt that, over time, can have a detrimental effect on your ability to do just about anything.

Yawning Newborn Baby
[public domain image]

The vast majority of people in the US (all ages, all genders, all races) do not sleep well or for long enough, and new research in sleep medicine shows that this has a whole-body impact that can aggravate or even lead to other chronic illnesses like heart disease, diabetes and neurological disorders. When one considers that lack of sleep can lead to dangerous behaviors like drowsy driving, it's not a stretch to suggest that poor sleep has silently become both a public health and public safety crisis in this country.

Fortunately, many sleep-related problems and disorders can be prevented or treated easily with lifestyle changes, simple therapies, improved breathing devices and new classes of medications.

But how do you know if your sleeping life is problematic for you? It can be hard to know if you have apnea, for instance, if you do not have a bed partner witnessing you asleep and gasping for air. Lots of people sleep all night but, because they sleep in fragments (unknowingly), they do not wake up feeling refreshed and alert. Maybe it seems normal for some to take a long time to fall asleep, while others insist they can "get by" on 6 or less hours of sleep. But the facts bear out that none of these experiences or conditions can really be described as a normal part of the sleeping process.

In order to know what could be abnormal about sleep, it's probably best to start with an understanding of what's normal. Here are some basic notions about what NORMAL sleep resembles.

• The definition of sleep is not just "not awake." Sleep is "a physiologic state characterized by decreased consciousness, metabolism and movement." Sleep is not a state of unconsciousness, by the way. Your brain is quite active while you sleep; you just don't have any awareness of all the electrical and chemical activity taking place in your brain (Spriggs, 2010).
• Most people need to sleep around 8 hours a night. That may seem like a lot in our time-pressed world, but the fact is we are generally "entrained" (or matched) to a circadian system that ties in closely with the day and night cycles of the earth. Our circadian systems effectively shift into sleep mode by way of chemical and neurological processes that require sleeping for about 8 hours.  It's normal to sleep, in other words.
• Several factors affect your ability to sleep. Light (or lack thereof) is perhaps the most effective influence over sleep cycles, but other factors include body and room temperature, eating habits, drug use (even legal and prescribed) and your daily level and timing of physical activity. 
• Sleep is ruled by a complicated network of systems inside the brain which regulate sensory information, body temperature, breathing, blood pressure, alertness and sleep drive. It's not just the body shutting down; in fact, it's quite the opposite.
• The body has a sleep drive, which is similar to a sex drive or a thirst or hunger drive. Basically, your body develops pressure to sleep during the day's deprivation of sleep. The more awake you are over a long period of time, the higher your drive to sleep will become (this is a simplification of a more complex process, but I think you get the picture).
• There are two states of sleep: REM and NREM sleep. REM stands for "rapid eye movement" sleep and indicates when the brain has reached a stage of sleep in which body processes shift and the brain becomes as active as if it were awake. The eyes dart back and before beneath the eyelids; this is the stage where most dreaming takes place. REM sleep is the stage when the brain is in recovery mode, healing and repairing itself after a long day of hard work. NREM, or Non-REM sleep, generally leads up to and away from REM sleep. There are 3 stages of NREM: stage N1 transitions from wakefulness to stage N2 sleep, which shows signs of neurological and physiological shifts which represent the body falling to sleep. Stage N3 is the deepest, dreamless phase of sleep which helps aid the body in recovering from the physical stresses of the day.
• Periods of REM and NREM alternate as we sleep in cycles that last about 90 minutes each.
• Sleep efficiency is a way to measure how much sleep you actually experience while in bed. Normal sleep efficiency is around 90% of total sleep time. In other words, if you are in bed for 8 hours, you would have a normal sleep efficiency if you slept at least 7 hours and 12 minutes of that 8-hour period. Not surprisingly, an insomniac will have a lower rate of sleep efficiency, as they are in bed for quite a while before they fall asleep, or they may waken early and never return to sleep, or they might experience both problems. 
• Related to sleep efficiency is sleep latency, which is the measure of how long it takes to fall asleep (the point of sleep onset). Most people take anywhere from 5 to 20 minutes to fall asleep (or to return to sleep after waking in the middle of the night).
• One's ability to sleep is affected by body chemistry (hormone changes, in particular) as well as by sleeping environment (how light, how quiet, how comfortable, etc.) and other physiological factors (like chronic pain or allergies). 
• One's ability to wake up is also affected by similar factors. New mothers know very much how easy it is to awaken upon the sound of their crying baby. This has a hormonal component as well as a physiological one and is quite normal. 
• An occasional awakening at night to use the bathroom or get a drink of water isn't abnormal, but regular and/or multiple awakenings every night might suggest something is amiss.
• Other things to know about normal sleep:
• You don't have to lie down or even shut your eyes to fall asleep. 
• Your body typically undergoes a sensory blunting and almost complete paralysis as part of the normal sleeping process (specifically, during REM sleep).
• Memory consolidation is one of the key activities that takes place while you sleep.
• Dreaming is a normal function of sleep.

Understanding what comprises normal sleep is key to recognizing when one's sleep processes or habits aren't in balance. Awareness makes all the difference in the world. If you aren't feeling rested every morning when you wake up, it's high time you found out why. Chances are good it'll be an easy fix and then you can move on, with more energy and better health.


Reference
Spriggs, WH. (2010). Essentials of Polysomnography. Sudbury, MA: Jones and Bartlett Publishers.

Sleep Hygiene Tip of the Week || Rise time versus Bed time... which is better?

We're a culture in perpetual motion, so it's hard to always have the same sleep schedule, day in and day out. Either it's travel that messes up our schedule, or the variations in morning and evening schedules that come from parenthood, or we might work jobs that don't support a regular sleep schedule.

So if forced to choose, which is better? Going to bed at the same time at night or getting up at the same time every morning?

Circadian resetting occurs at the time you awaken. What this means is that the morning light sends a signal through both your eyes and--believe it or not--your skin, which stimulates your wakefulness drive. If you get up at the same time of day, even as seasons shift, your body resets to the circadian rhythms of the planet, which more or less guide the processes of all living things. It's easier to stay on track if you get up at the same time every day. It's even better to GO OUTSIDE for even 10 minutes, as that short dose of sunlight (even if it's dim or overcast) is still brighter than the lights in your house, and this will help you fight sleepiness during the day.

At night, it's a good idea to try to stick to a bedtime schedule (especially for children or for people with challenging schedules where they have to work hard to make sure they get enough sleep between shifts). But sometimes you just aren't as sleepy at that time. No worries. Remember that wakefulness drive I mentioned earlier? It works in tandem with your sleep drive. We all have a built in drive to sleep (just like we have a hunger drive, or a sex drive, or a thirst drive). That drive is informed by how much we slept previously (that includes naps during the day). So if you normally go to bed at 9pm and get up at 5am, and you take a 2-hour nap at 1pm, you might not feel as sleepy later, at 9pm, because you actually banked a couple of hours of sleep, thus delaying your sleep drive. So what do you do? You just go to bed when you begin to feel drowsy and don't worry so much about what time the clock says. Your body has its own built-in clocks, it will let you know when it's time to hit the hay.

One thing to keep in mind... some people tend to have more "morningness" (aka "larks") while some people tend to have more "eveningness" (aka "owls). Neither is better than the other, they are simply tendencies ingrained into our biological clocks at a fairly early age. The time when you go to bed or rise should suit your lifestyle and your natural tendencies rather than follow a prescription set by somebody else (except in the case of children, who are still developing their sleep habits).