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Stages of Sleep
Sleep Needs
Sleep Debt and Its Effects
Hormones and Sleep
Women and Sleep
Sleep Disorders
Getting a Good Night's Sleep
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Good Night, Sleep Tight

Sleep is the one thing that humans are unable to give up for any length of time. Even more so than water or food, our body simply shuts down when deprived of sleep. Yet, according to the American Academy of Sleep Medicine (AASM), “more than 100 million Americans of all ages ... regularly fail to get a good night’s sleep” for one reason or another, leading to “a lowered quality of life and reduced personal health.”

Sleep is essential for tissue and cell repair, detoxification, and replenishing energy. Yet, while seemingly at rest, sleep also allows us to sort and store our memories and experiences, and somehow contributes to enhanced learning and mental performance. We still have much to discover about how sleep actually “works” to restore our bodies and our minds, and the growing field of sleep research is beginning to uncover the details of what happens when we are “at rest” during sleep.

In his book, The Promise of Sleep, Dr. William C. Dement writes that “most of us have the idea that sleep is a cessation of all activity, an oblivion we slip into where nothing happens.” In fact, this is far from the truth. Dr. Dement explains that “During sleep the brain releases new combinations of the hormones and chemical messengers that stimulate cellular activity throughout the body. … the sleeping brain actually appears to be more active than it is while awake.”

Stages of Sleep

There are at least five different recognizable stages of sleep, signified by very different types of brain wave activity and other physiological responses, such as heart rate, breathing, and body temperature. A discussion of the brain wave activity is beyond the scope of this newsletter, but the sleep stages can be simply characterized as follows:

As we progress through the stages of sleep, we go deeper into sleep, achieving higher levels of restoration or rejuvenation. The transition through the stages of sleep is somewhat linear, but also cyclical, and we may go in and out of the various stages of REM and non-REM sleep several times throughout the night. Light sleepers, or those with sleep troubles, may not reach stages 3, 4, or REM sleep every night, leaving them feeling tired and unrested—no matter how long they have been “asleep.”

Sleep Needs

We sleep because we need sleep. Deep, restorative sleep is one of the most important factors in our overall health and well-being throughout our entire lives. However, as we age, our sleep needs and cycles change, leading to changes in our sleep patterns.

The early years are characterized by many hours of deep sleep. Infants typically sleep 16 to 18 hours a day; by the time they approach age three, toddlers sleep closer to 12 hours a day. Children’s sleep needs decline further as they grow older until their daily sleep requirement settles at about 10 hours, continuing into adolescence.

It makes sense that babies and young children spend a lot of their sleep time in deep sleep because of their need for building muscle and repairing tissues and cells. Metabolic activity and body temperature both decrease during sleep, which conserves energy and provides a chance for tissues to grow and refuel. In addition to the spurts of growth hormone mentioned earlier, the blood supply to the muscles also increases, allowing the body to recover from the physical stresses of the day before. And, in the early morning hours just before waking, cortisol levels peak to help the body prepare for the demands of the day ahead.

Our Internal Body Clock

Each of us has our own internal timekeeper, or body clock, that governs when we need to sleep and wake up. The clock that drives our sleep patterns is located in a specific area of the brain behind the eyes called the suprachiasmatic nucleus, and it works by sensing light and dark. When our bodies are in balance, our internal clock regulates the time of our sleep, as well as certain hormones that are linked to sleep.

The mechanism that drives this clock is our circadian (or twenty-four hour) rhythm. The circadian rhythm typically has two periods during the twenty-four hour day in which we are most driven to sleep: the strongest occurs between 2:00 and 4:00 AM, and a second period is between 1:00 and 3:00 PM.

Circadian rhythms do not remain consistent as we age, although women have been found to hold onto their rhythms longer than men. However, circadian rhythms in women are more prone to disruption due to hormonal factors such as premenstrual syndrome or menopausal hot flashes.

The sleep cycle begins to change dramatically when puberty hits, and “hormonal developments are integrally tied to changes in teenagers’ sleep” according to Dr. Dement. Levels of the sex hormones such as testosterone, luteinizing hormone (LH), and follicle-stimulating hormone (FSH) begin to surge during puberty, and are produced in greater amounts during periods of sleep in both girls and boys. The onset of puberty is also characterized by a significant rise in the amount of growth hormone secreted, along with a decrease in the level of melatonin secreted. The decrease in melatonin, which is the key hormone that regulates the body’s internal clock, helps explain why teenagers tend to become more “owl-like” as they prefer to stay up later at night. They actually have more difficulty falling asleep at what their parents consider to be the proper bedtime, partially because of the drop in their melatonin level, and then are very hard to wake up in the morning for school because they may be in deep stages of sleep. In this way, adolescents can easily become sleep deprived—and even more impaired than others—because they still require about 10 hours of sleep per night.

The sleep habits of young adults continue to change as they juggle their independence, social lives, and demands of school or career. The reasons for these changes have as much to do with the lifestyles and demands at different phases in life as they do to changes in circadian rhythm or internal body clock (see Our Internal Body Clock). Eventually, the sleep patterns of middle-aged adults and seniors tend to become more like that of a “lark” whereby they fall asleep and rise earlier.

The amount of sleep we need, and the amount we’re usually able to get, continues to decline as we get older. Young adults typically get as many as three to four hours of deep REM sleep a night, and that amount declines to less than two hours for seniors. Between the ages of 40 and 65, we average about seven hours each night and, as we age, we enjoy less recognizable deep sleep, which means that the quality of our sleep decreases. As soon as restful sleep eludes us, we’re likely to begin to fret about it because it is difficult, if not impossible, to avoid the effects of poor sleep.

Sleep Debt and Its Effects

Most of us need about seven to nine hours of sleep each night for optimal functioning, but it’s probably no surprise that most of us get less than that. Every time we deprive ourselves of the sleep we need, even if it is only a few minutes a day, that period of sleep loss accumulates into a sleep debt. Eventually that sleep loss can overcome us, causing us to be irritable and lash out, act irrationally, make mistakes, perform poorly at school or work, or even fall asleep unexpectedly.

According to a series of studies described by Dr. Dement, we can avoid dangerously high sleep debt by adding back a relatively small amount of sleep to our normal sleep routine. The evidence suggests that accumulated lost sleep must be paid back at some time, hour for hour, and those who have succeeded in lowering their sleep debt usually report gaining a new sense of well-being. “If you miss three hours one night, you must sleep 11 hours the next night (three plus your normal eight) in order to feel alert throughout the day,” writes Dr. Dement. While it may be difficult to pay it back in one lump sum, it is important to work at keeping your sleep hours paid up, even if you do it just a few minutes at a time.

The long-term effects of sleep deprivation appear to be cumulative, so it is important to pay back sleep debt to avoid chronic health issues down the road. In addition to the obvious negative effects on alertness and cognitive function, studies have shown that sleep loss may speed up some aspects of aging and alter hormone levels. Sleep-deprived individuals have been found to have higher nighttime levels of the stress hormone cortisol and lower levels of thyroid-stimulating hormone, both of which are involved in regulating metabolism.

Other medical conditions potentially linked to chronic sleep deprivation are a weakened immune system, hypertension, heart disease, type-2 diabetes, and even obesity. Recent studies indicate that a chronic lack of sleep can lead to a deficiency of leptin, a hormone that controls appetite. Without adequate leptin levels, we tend to crave carbohydrates—even after eating—which can lead to overeating and contribute to obesity.

Hormones and Sleep

As you are probably beginning to realize, many different hormones are linked to or related to sleep; when their levels change or fluctuate, sleep is often affected. A hormone deficiency or imbalance can contribute to exhaustion and waking up feeling tired, among other symptoms. According to Dr. Thierry Hertoghe in his book The Hormone Solution, “correcting hormonal deficiencies can restore the days of sound, refreshing sleep” for many people. The key hormones affecting or related to sleep include:

Women and Sleep

The powerful role that hormones play in sleep helps us understand why so many women have difficulty falling asleep, or staying asleep, especially during times when their hormones are fluctuating.

The National Sleep Foundation’s Sleep in America poll surveyed over 1,000 women, and the results suggest that the biological conditions unique to women (i.e., menstruation, pregnancy and menopause) affect sleep quality. The poll found that nearly 70 % of the women surveyed had trouble sleeping at least a few nights per week, with almost 50% reporting having trouble sleeping every night or nearly every night. The resulting sleep deprivation can lead to daytime fatigue, irritability, brain fog, increased anxiety, and depression, among other conditions.

For many women, pregnancy is the first time in their lives when they notice a real change in their ability to sleep. Some may be quick to blame the problem on the discomfort associated with the growing fetus’ movements, but the hormonal changes that accompany pregnancy are more likely the culprits. Sleep researcher Dr. Kathryn Lee found that pregnant women’s sleep becomes disrupted as early as 11 weeks into pregnancy. One of the most common complaints is the need to make more frequent trips to the bathroom throughout the night, even before the expanding uterus begins to press on the bladder. This feeling of the “need to go” is more likely caused at this stage of pregnancy by the increased level of progesterone, which inhibits the contraction of the smooth muscles of the urethra and bladder walls.

A woman’s menstrual cycle may also have an effect on sleep, but those effects may be very different for different women. Some women report sleep disturbances due to bloating, cramping, and headaches the week prior to their menstrual flow, while others experience them during their period. The hormonal changes in women with premenstrual syndrome (PMS) include a decrease in melatonin, which when combined with the other discomforts of the menstrual cycle, can add to their sleep troubles.

Sleep disruptions are some of the most common symptoms of perimenopause, and restful sleep eludes many menopausal women for a variety of reasons. In fact, Dr. Walsleben reports that nearly two-thirds of women complain of insomnia during the years leading up to menopause. In The Pause, Dr. Lonnie Barbach reports that “A lack of sustained sleep is the pattern we see with menopause. Women seem to wake up repeatedly during the night because they need to urinate or have a hot flash or night sweat, or for no apparent reason at all.” This is especially true of women who are particularly sensitive to fluctuations in estrogen levels, which can cause bothersome symptoms that interfere with getting a good night’s sleep.

Because estrogens have been shown to enhance REM sleep, increase the time spent in REM sleep, and reduce the time it takes to get to REM sleep, researchers designed studies to determine the effects of estrogen therapy on sleep. Placebo-controlled studies involving pre- and post-menopausal women found that estrogen therapy helps women to fall asleep faster, decreases wakefulness after falling asleep, and increases total sleep time.

In the post-menopausal years, women frequently report different sleep problems, including sleep-disordered breathing or loud snoring, which leave them feeling sleepy during the day. According to the AASM, this “may be related to falling progesterone levels, since younger women who experience surgical menopause are also at increased risk of developing sleep-disordered breathing.”

Especially for women, changing hormone levels are almost always at the root of their sleep problems and represent the biggest obstacle to enjoying an uninterrupted night’s sleep. Understanding the hormonal effects, along with addressing environmental factors and lifestyle habits, may be the key to helping women get a good night’s sleep.

Sleep Disorders

Of course, factors other than hormones can be disruptive to your sleep. Sleep problems often begin to occur during young adulthood or middle age due to increasing responsibilities and stress, or life changes such as a new baby or job, or the aging process. While it helps to honestly analyze if any of these may be affecting your sleep, it is also important to realize that there are serious medical conditions that may be the cause for your sleep disruptions.

Some of the more common sleep disorders include:

Most often, the sleep disorders mentioned above can be effectively treated. Insomnia and depression are two more common sleep disorders that are less straightforward to treat, and they are often related, as depression may be the underlying cause of insomnia.

Insomnia is considered the common cold of sleep problems, affecting approximately one-third of American adults. It is the most common sleep problem among women; according to the Sleep in America Poll, more than 60% of the women respondents reported experiencing insomnia within the previous month.

Effective treatment of insomnia relies on identifying the underlying cause(s). The cause can be something serious such as depression and, since sleep and mood involve many of the same chemical messengers and hormones, it makes sense that the chemical changes that induce feelings of depression will likely affect sleep as well. Insomnia may also be caused by stress and a hormone imbalance, as mentioned throughout this newsletter.

Whatever the cause, if your sleep disruptions are affecting your quality of life, it is important to consult with a healthcare practitioner, especially if you think you may have a hormone imbalance or other medical problem.

Getting a Good Night's Sleep

The ability to fall asleep, stay asleep, and then wake up feeling refreshed seems simple when it happens with little effort, and we tend to take it for granted when it happens so easily. However, we really begin to appreciate how critical sleep is to our overall health and well-being when it becomes problematic. Important factors in getting a good night’s sleep include:


Connections is a publication of Women's International Pharmacy, which is dedicated to the education and management of PMS, menopause, infertility, postpartum depression, and other hormone-related conditions and therapies.

This publication is distributed with the understanding that it does not constitute medical advice for individual problems. Although material is intended to be accurate, proper medical advice should be sought from a competent healthcare professional.

Publisher: Constance Kindschi Hegerfeld, Executive VP, Women's International Pharmacy
Co-Editors: Julie Johnson and Carol Petersen, RPh, CNP; Women's International Pharmacy
Writer: Kathleen McCormick, McCormick Communications Illustrator: Amelia Janes, Midwest Educational Graphics

Copyright © September 2012, Women’s International Pharmacy. This newsletter may be printed from the PDF version and photocopied for educational purposes, provided that your copy(s) include full copyright and contact information.
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