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: What about Melatonin, anyway? America's favorite OTC sleep remedy may work... or not...

Melatonin, as a natural supplement for reclaiming sleep, has never been more popular. It is perhaps the leading "alternative" sleep aid out there. Not only is it cheap and easy to source, but there are thousands of evangelists for this exogenous form of a hormone we naturally produce on our own.

Does it work?

Some basics about melatonin, first.

• Natural (endogenous) melatonin is derived from the neurotransmitter, serotonin, in a chemical process which takes place only during the night. Endogenous melatonin is naturally low during the day and high during the evening as it is inhibited by exposure to light due to the ultrasensitivity of the pineal gland to circadian and seasonal rhythms and cues, the strongest of which is light.
  
• Melatonin is key to modulating the circadian clock in the brain because it signals day-night information to a specific pacemaker in the brain called the suprachiasmatic nucleus. However, secretion of endogenous melatonin is also easily altered by environmental factors like exposure to bright light during the evening or the introduction of a late meal or heavy exercise at bedtime. Other circadian rhythms in other parts of the body can be influenced by disruptions in endogenous melatonin secretion as well, including the digestive system, the systems which regulate core body temperature, even blood pressure and reproductive cycles.
  
• Endogenous melatonin also acts as a vasodilator in the skin, increasing blood flow which results in heat loss and lowered body temperature. These physiological processes, in turn, support the sleeping process.
  
• Interestingly, endogenous melatonin is not essential for circadian rhythms; the removal of the pineal gland shows very little impact on these rhythms in humans.
  
• Abnormalities in endogenous melatonin secretion are most commonly associated with the following three psychiatric disorders: Seasonal Affective Disorder (SAD) with winter depression, major depressive disorder, and premenstrual disorder (PMDD). These disorders, in turn, can have a major impact on sleep function, potentially leading to hypersomnia and overeating.
  
• While we secrete our own melatonin in the pineal gland, there is also a manmade form of melatonin (exogenous) which you can also take in pill form. It is rapidly absorbed (within 30 minutes) and has a 40-60 minute half life (meaning it is metabolized and eliminated within this amount of time).
  
• We can purchase exogenous melatonin as an over-the-counter drug because the FDA classifies it as a food supplement and does not require rigorous data supporting its safety, composition or effectiveness.
  
• The exogenous (manmade) form of melatonin is used in two ways: to potentially help shift circadian sleep phases into a more normal pattern, and to serve as a sleep inducer or maintenance drug. Its effect on the suprachriasmatic nucleus is directly related to the amount of endogenous melatonin already being supplied by the pineal gland: those with shortages in endogenous melatonin will feel stronger effects if they take exogenous melatonin. 

• Studies show varying rates of therapeutic success in using exogenous melatonin. The risks of using exogenous melatonin are still unknown; no public health risks have emerged anecdotally. The most common potential side effect is headache. It is considered nonaddicting.
  
• Researchers still cannot agree on an optimal dosage of exogenous melatonin for most people as they have yet to discover a consistent dose-response relationship in studies (the lowest amount which can be shown to be effective).
  
• The effectiveness of exogenous melatonin depends upon the time of day it is administered, though researchers have yet to define an accurate window of time for taking it; the range is as broad as 30 minutes to 3 hours. It has been noted that if people take exogenous melatonin during the day, it may result in impaired function while driving a car, operating machinery or during job performance.
  
• The reason why research is so inconclusive about exogenous melatonin usage resides in the fact that while many studies have been conducted, the variables (dosage, type of subject tested, timing of dosage) vary wildly and cannot be cross compared. 

So, does it work? You be the judge. Here are some articles to consider before jumping on the melatonin bandwagon.

Cleveland Clinic || Melatonin Supplement Review

Mayo Clinic/Dr. Brent Bauer || Is melatonin a helpful sleep aid — and what should I know about melatonin side effects?

Wise Geek || What Are the Pros and Cons of a Melatonin Sleep Aid?

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Resources consulted

"Biochemical Pharmacology of Sleep." Chokroverty, S. From Sleep Disorders Medicine; Butterworth Heinemann, 1999.

"Circadian Rhythm Sleep Disorders." Berry, RB. From Fundamentals of Sleep Medicine; Elsevier, 2012.

"Clinical Pharmacology of Other Drugs Used as Hypnotics." Buysse, DJ. From Principles and Practices of Sleep Medicine, eds. Kryger, Roth and Dement; Elsevier: 2011.

"Melatonin and the Regulation of Sleep and Circadian Rhythms." Guardiola-Lemaitre, B and Quera-Salva, MA. From Principles and Practices of Sleep Medicine, eds. Kryger, Roth and Dement; Elsevier: 2011.

"Pharmacologic Treatments: Other Medications." Krystal, AD. From Principles and Practices of Sleep Medicine, eds. Kryger, Roth and Dement; Elsevier: 2011.



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.  

Sleep Disorders 101 || What is Jet Lag Disorder?

Dry, bloodshot eyes can also
be a symptom of jet lag

Anyone who has traveled by air across time zones can relate to the some or all of the symptoms of Jet Lag Disorder, which can include:

• Disturbed sleep patterns (you can't sleep, you wake up too early, you experience excessive sleepiness during nonsleep periods of the day)
• Fatigue
• Trouble with focusing, attention, concentration on typical tasks
• Digestive issues (constipation or diarrhea)
• Heavy menstrual cycles
• General malaise
• Tired muscles

Jet lag is a temporary circadian rhythm disorder in which your body fails to acclimate immediately to a new time zone, leading to these potential symptoms. Generally it occurs after you cross more than two time zones. When you move forward or backward "in time," you are also moving forward or backward through cycles of sunlight, which is really where the problem comes in. Jet lag is about both time (your "body clock") and light. All living things entrain their sleep-wake (or active-inactive) rhythms to the rise and fall of the sun. Changing time zones means you are experiencing different blocks of both time and light than your body and brain are accustomed to. Another part of the brain, the pineal gland, requires exposure to light in order to produce melatonin, the hormone that helps you to fall asleep. If your travel times are at odds with your sleep patterns, it could be due to an imbalance in melatonin production caused by traveling across time (and light) zones.

Your body has a main biological "clock" in the brain--the Suprachiasmatic Nucleus or SCN--which notifies many other systems about what "time" it is. Indeed, each and every cell in your body is theorized to have its own body clock, which synchronizes with the SCN.

The digestive system is also thought to operate by its own clock, using both food consumption and light to set body rhythms in such a way as to conveniently limit digestive processes while you sleep. This is why you might, in fact, have digestive problems as a result of jet lag, as the digestive system clock is not in sync with SCN.

Having jet lag can be problematic because the times you are accustomed to eating or sleeping may not fit comfortably inside your new schedule. You may be excessively tired in the day just as everyone else is going outside to enjoy the day, or you may want to eat an overlarge meal in the middle of the night.

Jet lag symptoms typically set in within 24 hours of arrival at your destination. The farther you travel, the more severe or long-lasting your symptoms can be. Easterly travel usually results in more severe symptoms when compared to westerly travel, as well.

Researchers indicate that it takes about a day to recover for each time zone crossed. If you crossed five time zones, for instance, it will take you five days to recover from jet lag, either because you have acclimated to the new time zone or as a result of returning to your home time zone. Don't worry too much; for most people, jet lag is temporary and repairs itself. In their case, it's not a disorder at all, but a problem that fixes itself.

However, if you're a pilot or business traveler who flies frequently, Jet Lag Disorder can become an ongoing problem for you. Elderly people can also require more time to recover from jet lag as well.

If you want to avoid the symptoms of jet lag, you can try the following:

1. Carefully time your light exposure in the new time zone to "reset" your rhythms. Wear sunglasses in the morning on eastern time and in the afternoon on western time to trick your brain into resetting its rhythms.
2. Drink plenty of water; air travel can lead to dehydration which can then exacerbate many other kinds of problems, including jet lag.
3. Avoid caffeine, alcohol, stimulants and sedatives while in the air. For sedative or stimulant prescriptions, it might be better to start take them on local time when you arrive at your destination. Taking them while traveling in flight can aggravate jet lag as well.
4. Be prepared to adjust immediately to the local light and time zone you arrive at and expect to take a day to feel out of sorts.
5. If you are traveling for an important event or meeting where you need to be alert, you might wish to travel two days ahead in order to have time to adjust prior to your appointment.
6. Pharmaceutical treatments for Jet Lag Disorder including pharmaceutical options (sedatives such as benzodiazepines--so-called "Z" class drugs such as zolpidem [Ambien]-- and nonbenzodiazepines--triazolam [Halcion]). Remember, drugs can have side effects.
7. Light therapy, which involves timing your exposure to specific kinds of light using special lamps at certain times of day, can be a great non-drug alternative. There are travel lightboxes specifically used for this. 
8. Alternative treatments for Jet Lag Disorder include melatonin (you only need .5mg for it to be effective, despite over-the-counter doses of 2mg or more) and certain proprietary herbal blends (often including valerian, GABA or skullcap). The key to using melatonin is to time it with the dimming of daylight so your pineal gland can operate more efficiently. As for herbal blends, please check drug interactions and side effects before you take them as they can be dangerous if mixed with certain prescriptions.
9. It is always more important to wake up at the same time of day than to go to bed at the same time of day. This is because your exposure to morning sunlight helps set your wakefulness drive for the rest of the day. While traveling, you might try to artificially "reset" your rise time while in another time zone to match the one you have at home in order to help lessen the impact of jet lag.
10. While there is no official "jet lag" diet, it's good to practice eating more carbs before periods of sleep and protein rich foods during the times of day when you want to be most awake.
11. It's never a bad idea to sleep a little extra prior to traveling to lighten your sleep debt before you head out.
12. You can try to stay up later gradually, prior to your trip, for westerly travel, or go to bed earlier, prior to your trip, for easterly travel, to make the transition easier once you arrive.
13. Sleep on the plane if you expect to arrive at night anyway. This can help reset your sleep drive.