It's my pleasure to be here to teach you about insomnia and whether it's a complex symptom or syndrome.

The first question we need to ask is why is sleep important? Obviously we spend a large portion of our life sleeping — about a third for most people. It's important in development and aging; sleep changes over the life span. It's universal across species. So we do see sleep everywhere. But although we're all doing it, the function of sleep is still unknown.

What we do know is that there are different processes that control sleep and influence our sleep. We have the interaction of the sleep homeostatic drive and the circadian alerting signal. The sleep homeostatic drive is our sleep load; the longer we're awake during the day, the greater the sleep load, the more we want to sleep. If you have been up since early morning and it's now getting late at night, the later it gets, the more tired you are. Once you go to sleep, the sleep load decreases until the early morning hours when you wake up and it starts increasing again.

At the same time, we have the circadian alerting system, which works the other way around; so the sleepier you get, the more the circadian alerting signal allows you to stay awake. So in the evening hours, although we're very tired and have a high sleep load, it's the circadian alertness levels that allow us to continue to stay awake. Once we go to sleep, the circadian alerting signal decreases, allowing us to stay asleep throughout the night.

Then you get the interaction of the two, which is what happens to us throughout the day. So we're able to stay awake most of the day; we have a little dip in the afternoon, and then at night we're able to sleep until the morning and we get up again. This is the process and the pattern for most people, unless of course you have insomnia.

What is our definition of insomnia? Insomnia is defined as difficulty falling asleep, or difficulty staying asleep (maintaining sleep), or nonrestorative sleep, with the symptoms lasting a month or longer and — this is very important — these symptoms cause significant distress or impairment in functioning. So it's not only difficulty sleeping at night but the fact that that difficulty affects your ability to function during the day. In primary insomnia, the problem is not accounted for by any other sleep disorder or by any other comorbid condition.

In order to understand insomnia, we first have to understand what normal sleep is, and this is our picture of normal sleep. Most people fall asleep, go through stage 1, stage 2, go down into their deeper levels of sleep, and they come back up. They'll have their first rapid eye movement (REM) period generally 90 minutes after sleep onset, and the cycle continues that way throughout the night. Most of our deep sleep occurs in the first third of the night; most of our REM occurs in the morning hours.

This is what happens and what it looks like when you have insomnia. It might take longer to fall asleep, so you have the prolonged sleep-onset latency. There might be awakenings in the middle of the night, and these are long awakenings because people have difficulty falling back to sleep; that would be middle insomnia. Brief arousals are normal; that occurs in everyone. But there might be an early morning awakening, waking up earlier than you want to, and then being unable to get back to sleep.

So we have several definitions of types of insomnia. We have primary insomnia, which is insomnia that lasts a month or longer. It does account for functional impairment and there are no other etiologies to account for it. We also have secondary insomnia, which still lasts a month or longer, but is usually related to an underlying disorder. I want to point out that at the National Institutes of Health (NIH) Insomnia State of the Science Conference, the panel's final report suggested that what we've been calling secondary insomnia be called comorbid insomnia because that's really what it is.

How common is insomnia? There have been many studies looking at the prevalence of insomnia in the population and they show anywhere between 10% and 18% of adults report difficulty falling asleep for 2 weeks or longer. So, chronic insomnia affects around 10% of the population.

But although it's that common, it's rather rare for these patients to come in and talk to their physicians about the problem. These are data from one of the early National Sleep Foundation polls that showed that 70% of patients with chronic insomnia never discuss the problem with their physician. Only 6% came into their physician to talk about it, and 24% mentioned it when they happened to be seeing their physician for some other problem. Of the 6% who did go to see their physicians, most of them were speaking with their general practitioners or internists (62%) with smaller amounts seeing other types of physicians.

So it's a problem if these patients are out there, but they're not talking to you, which means you need to ask them about their sleep and whether they have insomnia. What kinds of symptoms should you ask about? This shows what patients with chronic insomnia report: 72% in that same poll from the National Sleep Foundation reported their main problem was waking up feeling drowsy or tired (they're waking up feeling that they just didn't have a good night's sleep); 67% reported waking up in the middle of the night; 57% reported difficulty going back to sleep after they woke up during the night; 56% reported difficulty falling asleep; and 44% reported waking up too early in the morning and being unable to fall back to sleep. Think about these symptoms because that, as I said, is what you need to be asking patients.

What happens to insomnia with age? The prevalence does increase, from the younger adults, 18 to 34 years of age, where it's only about 14%, to older adults, age 65 years and above, where it increases to about 25%, and that's from 1 study. Other studies have shown similar percentages, anywhere from 25% to 50% of insomnia prevalence in the older adult.

However, although the architecture of sleep does change with age, we know that beginning at about age 40 years, we start losing our deeper levels of sleep.

This meta-analysis of 65 studies showed that it is not this change in architecture that's affecting the ability to sleep; it's really all the other comorbid conditions that go on with aging that are affecting the ability to sleep. Sleep itself is remaining fairly constant from ages mid 60s to mid 90s; although sleep architecture is changing, other aspects of sleep are not in healthy older adults and that's the key. In healthy adults, sleep does not deteriorate.

Let's look at special populations where we start seeing changes with sleep. We can start by looking at gender; women have higher rates of insomnia, and part of that is probably secondary to the higher rates of anxiety and depression that are seen in women.

We also see changes in sleep with menopause; peri- and postmenopausal women have more sleep complaints than younger women, and about 41% of early perimenopausal women report difficulty falling asleep or staying asleep. Often the frequent awakenings suggest insomnia secondary to vasomotor symptoms. However, we see multiple awakenings that have nothing to do with hot flashes and so it's unclear how much the insomnia might be related to the hot flashes.

So there obviously are many factors that are causing insomnia, and it's important to understand that because you need to understand and determine the cause as part of the treatment of the insomnia. Some of the potential factors that will cause difficulty sleeping would include medical conditions, the medications that are used to treat the medical conditions, psychiatric disorders, prevalence or appearance of primary sleep disorders, poor sleep hygiene, and psychosocial factors. I'm going to tell you about the medical conditions and the medications.

Let's start with medical conditions. These also are data from the 2003 National Sleep Foundation poll that focused on older adults, and what it showed was that the more comorbid conditions an individual had, the more complaints they had of sleep. In people with no comorbid conditions, about 36% had problems with sleep. When there were 1 to 3 medical conditions, it was 52%; it went up to almost 70% with 4 or more medical conditions. And certainly in the elderly, most of them have more than 1 or 2 medical conditions and that probably is accounting for much of their insomnia.

What are the different medical conditions that cause difficulty sleeping? Obviously there are lots of them. This is just a short example of some of them, but pretty much any medical condition that causes any sort of discomfort is going to interfere with sleep. So headaches, chronic obstructive pulmonary disease (COPD), gastrointestinal (GI) changes, arthritis, neurodegenerative processes, coronary artery disease, congestive heart failure — all these conditions are going to cause difficulty sleeping.

Let's look at some of the specific conditions. Let's start with COPD: 50% prevalence of disorders of falling asleep and staying asleep are in patients with COPD, and 25% of patients with COPD complain of being excessively sleepy during the day. The forced expiratory volume in 1 second (FEV₁) and forced vital capacity (FVC) ratio predicts nocturnal hypoxemia, which is going to interfere with sleep. Hypoxemia is especially common in REM sleep in these patients, and correlates with increased arousals during the night as well as increased excessive sleepiness during the day. And yet oxygen therapy doesn't clearly improve sleep quality, although that's often the treatment that's given to patients with COPD. Improving air flow with inhalers, however, might improve both sleep quality and duration. So in patients with COPD, not only do you need to treat the COPD; you have to think about treating their insomnia and sleep problem as well.

How about gastroesophageal reflux disease (GERD)? As sleep states change, there's an increase in likelihood of reflux and the reflux itself is going to wake patients up; it produces arousal. Sleep apnea and GERD may co-exist in a patient and, therefore, you have to think not only about the GERD, but you have to think about whether the sleep apnea is present and then think about treating each of those appropriately. If sleep apnea is not present, then you have to go after treating the insomnia.

End-stage renal disease (ESRD): 50% of patients with ESRD complain of difficulty maintaining sleep. They have multiple awakenings during the night. Fifty-five percent of them complain of waking up too early in the morning and having difficulty falling back asleep. The pain, depression, and decreased functional status all correlate with the difficulty sleeping in these patients. And in hemodialysis patients, you have an increase in sleep apnea, an increase in restless leg syndrome and periodic limb movements, and an increase in early insomnia. On any hemodialysis unit, as you observe the patients, you can see their legs shaking and moving. Sleep apnea improves after dialysis, and patients with ESRD with anemia treated with epoetin alfa show improvement in sleep continuity and decreased number of leg kicks. There are approaches to treating some of the symptoms that these patients are experiencing. The important point is that when you have patients with these disorders, be sure that you think about the insomnia and think about treating it.

What about diabetes? Thirty-three percent of diabetics demonstrate difficulty staying asleep, and it's associated with nocturia, leg cramps, restless legs, periodic limb movements, leg pain, and cough — the coughing itself disrupts sleep. The severity of the sleep disruption correlates highly with poor control of the diabetes, so again, you need to get the primary condition under control but you also need to treat the sleep. And diabetics also have increased risk of sleep apnea.

What about the medications that we use to treat all these medical conditions? They in themselves are going to affect sleep.

All of the following drugs are known to cause difficulty sleeping: central nervous system (CNS) stimulants, antihypertensives, respiratory medications, chemotherapy, decongestants, hormones, and psychotropics. Think about the patients that you see in your practice; how many of them take at least 1 of these classes of medications? How many take more than 1 of these classes of medications? Probably many of your patients take them. And for that reason, we have to think about how these drugs are affecting sleep. Sometimes adjusting the dose of these medications, or adjusting the time of day that they take these medications, is enough to improve sleep, but if not, then we need to think about adjunctive therapy for the insomnia.

We also have to think about the medications that are sedating, such as the longer-acting hypnotics, antihypertensives, antihistamines, tranquilizers, and some of the antidepressants. These are the drugs that should be taken later in the day to actually sedate the person at night to help them sleep, while the activating drugs should be taken earlier in the day to help people stay awake and not interfere with nighttime sleep.

To summarize, insomnia is very common in the population; chronic insomnia is probably found in about 10% of adults. The prevalence of insomnia does increase with age, but it's not age per se that causes that increase; it's the other comorbid conditions and medications that are found in the elderly that are likely causing the increased prevalence of insomnia. Women have higher rates of insomnia and insomnia in women is more likely associated with higher rates of anxiety and depression, and may be related to menopause and symptoms of menopause. Comorbid illness has a profound effect on sleep and we have to remember that when we're treating these patients. And the medications that are used to treat both the medical and the psychiatric conditions will cause insomnia and those must also be considered when treating a patient for their difficulty sleeping.