Hi. My name is Dr. Ron Chervin, I direct the Sleep Disorder Center at the University of Michigan in Ann Arbor Michigan. I am a professor of neurology and I also hold the Michael S. Aldrich Collegiate professorship in Sleep Medicine. It's my honor today to introduce you to a portion of this course that deals with clinical sleep medicine. So, much of what you heard up to this point has had to do with the pathophysiology of sleep and what we're transitioning now is into a phase of the course where we actually discuss what can go wrong with sleep, and what creates sleep disorders in many of our patients. So, to give you an idea about just how common sleep disorders are, first of all, if you just think about it, we all sleep for about a third of our lives. And so, it's not that surprising to think that although we've largely ignored disorders that happened during our sleep for many years, again in the last few decades, we realize that there really are many types of disorders that happen in that one third of our lives and that those disorders are actually quite common. So, about one in three or somewhere around 30% of people are believed to suffer from significant insomnia for a somewhat prolonged period at some point in their lives. And at least one in 30 persons, and we'll talk about that and maybe even quite more common, at least one in 30 suffer from obstructive sleep apnea syndrome which is another type of common and consequential sleep disorder that we'll talk about later, and about one in 3000 people suffer from narcolepsy and so even that which is considerably less common than obstructive sleep apnea is not uncommon. So here I've listed out for you, you're using very conservative, again a conservative estimate of a three percent rate for obstructive sleep apnea. Even when you look at it conservatively, it's more common than many other disorders that you may have heard about more often, or had this sense that they may be more common. So, migraine started because I mean to say that it requires the attention of a specialist is less common than obstructive sleep apnea. Epilepsy is only maybe a fifth as common or less than obstructive sleep apnea. Different forms of parkinsonism, multiple sclerosis, myasthenia gravis, and Guillain-Barre syndrome are all significantly less common than obstructive sleep apnea. And obstructive sleep apnea is just one type of sleep disorder. The other thing that we've learned in recent decades is the huge impact that disorders during our sleep at night can have on our entire health and our daytime function. So, we now have good evidence that sleep disorders have impact on how long we live and the quality of life, our productivity at work have huge impacts on overall medical costs to insurers and health systems and society, not to mention personal families and individuals. Sleep disorders cause motor vehicle crashes. They can have very severe impact on cardiovascular health over time. They have interactions and impact on pulmonary health and many different types of pulmonary disorders. Sleep disorders seem to be very meshed and intertwined with mental health and psychiatric disorders. We believe that some sleep disorders and particularly sleep apnea may affect the post-operative safety and survival in a very operative setting. We're increasingly understanding serious impact on learning and cognition, on growth, on metabolism, many people think that obstructive sleep apnea is almost part and parcel really of the metabolic syndrome that has been such a concern with the obesity epidemic. And in fact, sleep disorders are intimately entwined with obesity and particularly sleep apnea. And finally, we're realizing that sleep disorders can have impact on inflammation and systemic inflammation in the body as well as status of our immune systems. So, just picking on one of those and the issue about motor vehicle crashes, this quotation from one of the experts in the field, Dr. Mark Mahowald, ''Fall-asleep car crashes number in excess of 100,000 per year in United States, resulting in at least 1500 deaths. And for perspective fall-asleep crashes may kill more young Americans than alcohol-related crashes.'' So, with that brief introduction, next we'll talk about how we as sleep physicians approach patients with sleep complaints when we see them in the clinic.