scientists do not fully understand the function of sleep, but there is plentiful evidence of the effects of insufficient sleep. Population-based studies have contributed to explaining the negative consequences of sleep deprivation across a wide range of populations and sleep disorders. The consistency in findings is notable, given the heterogeneity in populations studied, variability of individuals’ responses, methods used to measure sleep, and outcomes examined. Less is known about the effects of strategies to decrease the negative consequences of sleep disorders, but there is growing evidence that treatment of some disorders improves selected outcomes. At the community and population levels, there is a need for better communication about the personal and societal risks associated with sleep loss.
The most specific consequence of sleep loss is excessive daytime sleepiness. A recent survey revealed that 19.5% of U.S. adults are moderately to excessively sleepy. Nearly 18% reported falling asleep in situations that require a great deal of attention. The highest association was with obstructive sleep apnea, but people with insomnia and sleep duration less than 6 hours and those with depressive disorders were also at risk (http://www.sciencedaily.com/releases/2010/06/100608091852.htm).
Sleep loss also contributes to decrements in cognitive function, including attention, vigilance, memory, and decision making. Many individuals, including some who work in situations requiring high levels of vigilance (e.g., commercial drivers, health care workers), have involuntary micro-sleeps, variable performance, increased errors, and slow response time (IOM, 2006). Although individual responses to sleep loss are highly variable, the cognitive effects of sleep loss are often subtle and many individuals and their health care providers are not aware that their performance is compromised.
Injury to Self and Others
Sleep loss contributes to excessive risk of injury to the person with sleep disorders and others. For example, obstructive sleep apnea is associated with a three-fold risk in the likelihood of motor vehicle crashes, but this relationship is not dependent on excessive daytime sleepiness (Rodenstein, 2009) and not dose-dependent. It may be secondary to more subtle effects of sleep-disordered breathing on cognitive function. Likewise, insomnia is associated with increased rates of nonmotor vehicle-related accidents (Daley, Morin, LeBlanc, Gregoire, & Savard, 2009). Sleep loss was associated with errors that led to major tragedies, such as the Exxon Valdez oil tanker spill, the nuclear reactor disasters of Chernobyl and Three Mile Island, and commercial and noncommercial motor vehicle crashes (IOM, 2006), among others. Health care workers, including nurses, are particularly vulnerable to the personal health (e.g., medical morbidity, motor vehicle crashes) and work performance (e.g., medication and other errors) consequences of prolonged work hours and shift work (Geiger-Brown & Trinkoff, 2010; Rogers, 2002; Scott et al., 2007). Although the number of hours per week that medical residents are permitted to work is limited by regulations, no such policies exist for nurses.
The public health burden of sleep disorders is enormous. Emerging evidence convincingly documents that sleep loss and sleep disorders contribute to highly prevalent chronic conditions in adults and children, including obesity, diabetes, and impaired glucose tolerance, cardiovascular disease, anxiety, depression mood, and alcohol use (IOM, 2006). The effects of specific sleep disorders and their treatment are explained throughout the chapters of this book.
Sleep loss and sleep disorders also contribute to mortality. Several large prospective studies have documented a U-shaped relationship between short and long sleep durations and age-adjusted mortality, after controlling for relevant covariates (IOM, 2006). Less than 5 hours sleep was associated with a 15% increase in mortality risk, but long sleep durations (>9 hours) also confer risk. These findings continue to be replicated in more recent reports. For example, a prospective study of ethnic Chinese in Taiwan revealed a similar curvilinear relationship between sleep duration and all-cause mortality. Insomnia and short sleep duration were associated with deaths from cardiovascular disease (Chien et al., 2010). In a recent review of 23 studies (Gallicchio & Kalesan, 2009), both long and short sleep duration were associated with all-cause and cardiovascular and cancer-related mortality. Limitations to this body of research include frequent reliance on cross-sectional studies and inconsistent control for potential confounding variables. For example, depression and low socioeconomic status were associated with both long sleep duration and mortality (Patel, 2007; Patel, Malhotra, Gottlieb, White, & Hu, 2006).
Quality of Life
Sleep disorders and sleep loss are associated with decrements in multiple dimensions of quality of life. For example, obstructive sleep apnea was associated with vitality, and insomnia was associated with all dimensions of the Medical Outcomes Study. SF-36 in the Sleep Heart Health Study, a population-based study (Baldwin et al., 2001), and similar associations are present in many other studies, for example (McCall et al., 2010; Redeker et al., 2010; Rosen, Palermo, Larkin, & Redline, 2002; Wesstrom, Nilsson, Sundstrom-Poromaa, & Ulfberg, 2008). However, health care professionals have yet to fully recognize the problem.
Sleep loss and sleep disorders are responsible for billions of dollars of direct and indirect costs, including the expenses of treatment, diagnostics, the services of health professionals, and hospital services. Indirect costs are attributed to morbidity, disability, injury, accidents, lost productivity, inability to cope with shift work, increased alcohol consumption, and absenteeism (Hossain & Shapiro, 2002), and errors (including medical). An extensive review of information on costs is provided in an Institute of Medicine report (IOM, 2006). Researchers in Quebec (Daley et al., 2009) found that the costs associated with health care consultations, prescription, and over-the-counter medications; the use of alcohol as a sleep aid; work absences; and decreased productivity cost an average of $5,000 Canadian per person among those meeting full criteria for insomnia and $1,400 for people with insomnia symptoms, with 76% of the cost associated with work absences and decreased productivity (Daley et al., 2009).
There is considerable information on the efficacy of treatment on sleep itself (i.e., effects detected with well-controlled, randomized clinical trials in homogeneous samples), much of which is reviewed in subsequent chapter of this book. However, there has been little research on the effectiveness (effects of sleep treatment in heterogeneous patients in usual clinical settings), and improvement in sleep characteristics does not necessarily lead to detectable improvements in morbidity, mortality, quality of life, daytime performance, and injury risk. Reasons for this are multifactorial and include the subtle and multidimensional nature of these consequences, as well as lack of consensus on the definition of daytime sleepiness/impairment related to sleep and lack of sensitive and specific methods for measuring these phenomena.
Studies of comparative effectiveness and costs of sleep disorders treatments are urgently needed (Espie, 2009; McDaid et al., 2009; Reeder, Franklin, & Bramley, 2007; Roth, 2009), but these types of analyses are just beginning. For example, CPAP treatment of moderate-to-severe sleep apnea was cost-effective over time, compared with dental devices and placebo (McDaid et al., 2009). Nurse-led CPAP titration in the home was less expensive and had comparable outcomes than traditional laboratory based physician-led treatment in Australia (Antic et al., 2009); in addition, a “stepped care” approach to behavioral insomnia treatment may be more efficient and cost-effective than full multi-session traditional cognitive behavioral therapy. These and other innovations may ultimately lead to improved outcomes and lower costs, but empirical evidence is needed.
Role of Nurses and Other Health Care Providers
Despite the dramatic increases in the science of sleep and sleep disorders, sleep disorders and their consequences remain underdiagnosed and undertreated by many who provide care for adult and pediatric patients (IOM, 2006). Early recognition of sleep-related symptoms is likely to lead to accurate diagnosis, effective treatment, and reduced likelihood of comorbidity—all of which may reduce the indirect and direct costs of sleep disorders. Therefore, there is a need for nurses to be proficient in the use of relevant sleep diagnostic classification systems (i.e., nosologies).