August 2012  << Back  

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Sleepiness: Causes, Consequences and Treatment

Richard Balon, MD

Wayne State University, Detroit, MI, USA

Edited by Michael J. Thorpy and Michel Billiard. New York, NY: Cambridge University Press; 2011; ISBN: 978-0-521-198868, pp 494; $160 (hardcover).

Sleepiness seems to be a reality of our life. The hectic pace and multiple demands of our lives leads to inadequate sleep. As Dr. Thomas Roth writes in the Foreword to this volume on sleepiness, “Inadequate sleep at night is probably the most common cause of sleepiness. Among the general population, insufficient duration of sleep at night is thought to be the cause of excessive sleepiness. In contrast, among patients and the elderly population, it is the fragmentation of sleep which leads to excessive sleepiness. Importantly, in clinical populations, a variety of pathologies as well as their treatments also give rise to excessive sleepiness” (p xi). The editors of this book put together an international team of 63 authors to address “all one can know about sleepiness, its causes, consequences, and treatment.”

The book consists of a Foreword, Preface, and 40 chapters divided into 4 major sections. In the mentioned Foreword, Dr. Roth eloquently defines some basic terms in the area of sleepiness. He writes, “The term ‘sleepiness’ is used to describe the normal biological drive for sleep.… Excessive sleepiness is used to describe a biological drive for sleep whose intensity is such that there is an inability to stay awake, and hence a high propensity to fall asleep even in situations that are inappropriate, interfere with activities of daily living, and can be harmful to the individual” (p xi). He also adds that, “The pervasiveness of sleepiness in our society is evidenced by two societal indicators. These are oversleeping on weekends and caffeine consumption” (p xi). The Foreword further expands into explaining various terms such as masking (some factors such as motivation, stress, and level of activity mask our sleepiness) and misattribution. A person with sleep apnea may state that driving a car, attending a meeting, etc., makes him or her sleepy while he or she is sleepy because of sleep apnea. The Foreword also summarizes major issues of the area of sleepiness with most of them addressed later in various chapters.

The first section, “Introduction,” consists of 9 chapters addressing issues such as epidemiology of excessive sleepiness; the neurochemistry of excessive sleepiness; functional imaging of sleepiness disorders; clinical evaluation of excessive sleepiness patients; objective measures of sleepiness; subjective measures of sleepiness; cognitive aspects of sleepiness; motor vehicle driving and sleepiness; and medico-legal consequences of excessive sleepiness. The chapter on epidemiology emphasizes that a uniform operational definition of excessive sleepiness is still missing (p 10) and therefore the prevalence of excessive sleepiness may vary widely (eg, 25% in Japan and 21.5% in Mexico). The chapter on clinical evaluation reviews questions useful for characterization of excessive sleepiness (eg, Does sleepiness only occur when the patient is sedentary or when active? Does sleepiness occur during situations that would compromise the patient’s or others’ safety, eg, when driving? [p 39]). The chapters on objective and subjective measures of sleepiness provide a good description and explanation of tests such as the Multiple Sleep Latency Test, Maintenance of Wakefulness Test, Stanford Sleepiness Scale, and others. The chapter on cognitive effects of sleepiness points out that “sleepiness has wide-ranging adverse consequences for attention and vigilance, executive functioning, and learning and memory” (p 78).

The 15 chapters of the second section (“Sleep disorders and excessive sleepiness”) review sleep deprivation as a biomarker for identifying and predicting individual differences in response to sleep loss; narcolepsy; idiopathic hypersomnia; Kleine-Levin syndrome; menstrual-related hypersomnia; sleepiness due to sleep-related breathing disorders; daytime sleepiness in insomnia patients; sleepiness in advanced and delayed sleep phase disorders; shift workers and sleepiness; sleepiness in health care workers (namely residents); sleepiness in the military; time-zone transition and sleepiness; restless leg syndrome and periodic limb movements and excessive sleepiness; long sleepers; and sleepiness in children. These chapters are brief, informative, and well written. Those interested in narcolepsy will appreciate the discussion of 1 new treatment for this disorder—sodium oxybate. The chapter on sleepiness in health care workers emphasizes that sleep appears to benefit all classes of memory (p 208) and medical students use all forms of memory to learn new facts and therefore need a good sleep. This chapter also reviews the regulation of work hours in countries other than the United States (the Working Time Directive, an European Union eirective, limits all health care workers to 48 hours per week). Finally, this chapter provides further guidelines for shift workers. I liked the detailed advice on combating travel fatigue and jet lag (which are 2 different things!) discussed in the chapter on time-zone transitions. The chapter on long sleepers presents an interesting notion that extended sleep, even in good sleepers, can be associated with sleepiness.

The third section, “Medical, psychiatric and neurological causes of sleepiness,” discusses in its 10 chapters a chronobiological approach to depression and sleepiness; aging, Alzheimer’s disease, and sleepiness; excessive daytime sleepiness in Parkinson’s disease; myotonic dystrophy and sleepiness; posttraumatic sleepiness; genetic disorders and sleepiness; brain tumors, infections, and other CNS causes of sleepiness; hypothyroidism and other endocrine causes of sleepiness; toxic and metabolic causes of sleepiness; and excessive sleepiness due to medications and drugs. Again, these are solid mini-reviews of each topic.

Finally, the fourth section, “Therapy of excessive sleepiness,” deals with the following treatments: amphetamines, methylphenidate, and excessive sleepiness; modafinil/armodafinil in the treatment of excessive daytime sleepiness; sodium oxybate for the treatment of excessive sleepiness; caffeine and other alerting agents; histamine receptor antagonists, hypocretin agonists, and other novel alerting agents; and behavioral and psychiatric treatments for sleepiness. The chapter on caffeine includes a table on caffeine content of selected foods and beverages—a grande Starbucks brewed coffee and the energy drink Spike Shooter are clear “winners” with 320 and 300 mg of caffeine per serving, respectively. The last chapter is focused on behavioral and psychiatric strategies and suggests scheduled naps, dietary changes, behavioral strategies for consolidating nighttime sleep, and further general behavioral strategies for work, home, and school to manage narcolepsy. The discussion of using cognitive-behavioral therapy for excessive sleepiness is surprisingly thin.

This volume provides a lot of important and interesting information about causes, consequences, and treatment of excessive sleepiness. The Foreword also emphasizes what is still missing in this area—eg, a reliable, valid, rapidly derived measure of sleepiness, more genetic research (eg, what are the genes that differentiate individuals who show significant impairment from the various causes of sleepiness from those who do not? Are there adaptive mechanisms to decrease the accumulation of sleepiness? [p xiii]), and better public education about sleepiness. Nevertheless, even without answers or coverage of these areas, this book is a great overview of sleepiness and would be a welcome addition to the libraries of clinicians treating sleep disorders, psychiatrists dealing with various disorders associated with sleepiness, and teachers of residencies and sleep fellowships.