Consequences of Insomnia, Sleepiness, and Fatigue

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Insomnia, Sleepiness, Fatigue, and the Consequences

Insomnia, sleepiness, and fatigue kill! This dramatic statement conveys the magnitude of the morbidity and mortality that our society is experiencing. This column highlights the clinical and statistical correlations between our society's "24/7" work, travel, and recreational lifestyles, and subsequent associated disease, injury, accidents, and deaths. I begin with a discussion about insomnia, sleepiness, fatigue, and the consequences, and then I focus on issues pertaining to shift workers who may comprise more than 20% of the primary care patient population. These workers experience less sleep, more illness, and more accidents (both on and off the job site) than nonshift workers.^[1]

The Characterization and Prevalence of Insomnia

The World Health Organization and the World Federation of Sleep Research Societies define insomnia as a repeated difficulty with sleep initiation, maintenance, duration, and/or quality of sleep, which occurs despite adequate opportunity and time for sleep, and results in daytime impairment. Insomnia is further categorized as (1) transient, lasting less than 1 week; (2) short-term, lasting from 1 to 4 weeks; and (3) chronic, lasting longer than 1 month. The prevalence of transient and short-term insomnia symptoms in the general population is approximately 30% to 50%. Chronic insomnia, whether primary or secondary in nature, has a prevalence of 9% to 15%, and occurs more frequently in women, older adults, and patients with chronic medical and psychiatric disorders.

Primary vs Secondary Insomnia

The pathogenesis of primary insomnia (eg, idiopathic, psychophysiologic, or paradoxical) is unknown, but is believed to be associated with a state of hyperarousal.^[2] Patients with primary insomnia have been shown to have higher global cerebral glucose metabolism in positron emission tomography imaging studies both when awake and asleep, increased beta activity on electroencephalography during sleep, an elevated 24-hour metabolic rate, and higher rates of secretion of adrenocorticotropic hormone and cortisol.^[3] Sleep debt has been shown experimentally to have a harmful impact on carbohydrate metabolism and endocrine function. In a study with a cohort of young men, glucose tolerance and thyrotropin levels were significantly lower after 4 hours of sleep restriction for 6 consecutive nights.^[4]

Secondary causes of insomnia include active psychosocial stressors; lifestyle habits that impair sleep; psychiatric disorders (such as anxiety or depression); medical conditions (eg, restless legs syndrome, chronic pain, and hot flashes); other sleep disorders (eg, sleep-related breathing or circadian rhythm disorder); and drug or substance consumption, discontinuation, and abuse.^[5]

Cognitive and Psychological Consequences of Insomnia

Whatever the cause, insomnia results in sleepiness, fatigue, and cognitive impairment. Excessive sleepiness has been linked to learning disabilities in children and cognitive and memory problems in adults. These deficiencies have been shown not to be related to the specific sleep disorder but, rather, are caused by the sleepiness associated with the disorder.^[6,7]

Zammit and colleagues^[8] found that insomnia and its associated daytime sleepiness had significant negative effects on cognitive functioning and impaired their subjects' ability to perform ordinary daily tasks. Patients with insomnia scored significantly lower on the Medical Outcomes Study Cognitive Scale than controls, thereby reflecting problems with concentration, memory, reasoning, and problem solving.^[8] In a study by Breslau and associates,^[9] patients with insomnia were nearly 4 times more likely to suffer major depression than those without insomnia. Similar elevated risks were found for anxiety disorder and drug and alcohol abuse and dependence.^[9]

The Impact of Sleepiness on Accidents

Sleepiness increases attention lapses, slows reaction time and cognitive processing, and makes the drowsy driver as dangerous as one who is impaired by alcohol. This was demonstrated by results from studies with adults who were exposed to extended periods of wakefulness and then subjected to grammatical reasoning and psychomotor (computerized test of hand-eye coordination) testing. After 24 hours of wakefulness, the subjects' performance was equivalent to that seen in persons who are legally intoxicated (blood alcohol concentration, .10%).^[10] Moreover, fatigue can augment the effects of alcohol and medications. Ingesting 1 oz of alcohol after being restricted to only 4 hours of sleep has the effect of ingesting several alcoholic drinks, resulting in severe impairment.^[11]

The National Highway Traffic Safety Administration (NHTSA) estimates that at least 100,000 crashes and 1500 deaths annually are attributable to sleepiness/fatigue.^[8] This equates to an automobile accident every 5 minutes and a fatal accident every 6 hours. These crashes alone represent $12.5 billion in lost productivity and property damage. Drowsiness also plays a role in crashes assigned to other causes. NHTSA estimates that another 1 million crashes (1 of 6 of the total) result from driver inattention, and clinical studies show that sleep deprivation and fatigue make such attention lapses more likely to occur.^[8,9] Even the sleep changes that are associated with daylight saving time and during the holiday seasons, with the added stresses of shopping, parties, traveling, and year-end workloads, can result in more accidents.