Impairments and Burdens

Impairments and Costs Associated with Insomnia

Insomnia is associated with a variety of daytime impairments. Clinical practitioners have long been aware that a poor night’s sleep is generally followed by daytime sleepiness and fatigue. However, research over the past few decades increasingly indicates that poor sleep is not only associated with cognitive and emotional deficits but also leads to cardiometabolic, endocrine, and a complex array of systemic abnormalities.

Cognitive Deficits

Compared with individuals without sleep complaints, patients with insomnia report many cognitive symptoms and impairments (Table 5-1), often feeling sleepy and fatigued. Many have trouble with memory and organization, and are generally just not as “mentally sharp.” These abnormalities are generally viewed to be temporally associated with the emergence of insomnia. Some of these deficits have received objective confirmation from tests involving challenging reaction-time tasks. One study showed that patients with insomnia had longer response latencies and more variability in their reaction times across many performance tests than did normal sleepers. Patients with insomnia also responded more slowly and showed more attentional and behavioral instability in their performances (Figure 5-1).

Another study found that patients with insomnia exhibit deficits in higher-level neurobehavioral functioning (e.g., switching attention and working memory) but not in basic attention. This suggests that neurobehavioral deficits in insomnia may be due to neurobiological alterations rather than sleepiness resulting from chronic sleep deficiency.

Enlarge 

Enlarge 

Reduced Functionality

Insomnia is associated with an increased risk for injuries and accidents. Those with insomnia have been shown to have 3.5 to 4.5 times more accidents in general, 1.5 times more work-related accidents, and 2.5 times more motor vehicle accidents. Poor prior sleep quality is a major factor in predicting auto crashes that result from falling asleep at the wheel (Figure 5-2).

Individuals with insomnia also have been shown to have poorer job performance. A questionnaire by Leger and associates at Stanford University compared the socio-professional and medical consequences in people with and without insomnia. People with severe insomnia reported a higher rate of absenteeism and missed work twice as often as good sleepers. In addition, they had more problems at work than good sleepers, including decreased concentration, difficulty performing tasks and more work-related accidents.

Insomnia can have unique consequences in the elderly population. Those >65 years of age with insomnia suffer from a greater number of falls than their counterparts without insomnia. In one study of >34,000 nursing home patients, those with insomnia were seen to fall 1.52 times more often than those without insomnia. This number was not attributable to hypnotic use, and the use of these medications was not predictive of fall. In fact, those with insomnia who were treated had fewer falls (1.32 times compared with 1.52).

Enlarge 

Quality of Life

Patients with insomnia have a significant reduction in quality of life, which is proportionally related with the severity of insomnia. In community samples, people with insomnia score lower on all subscales of the SF-36 questionnaire indicating impairments across multiple quality of life domains, including body pain, general health, mental health, emotional role, social and physical functioning, and vitality, compared with those without sleep complaints (Figure 5-3). The SF-36 is a scale used to provide perceived health status in eight domains measuring limitations of physical, social, or daily activities resulting from health or emotional problems, physical health problems limiting usual activities, body pain, general mental health, vitality and general health perceptions. The SF-36 is useful in comparing the impact of disease and the efficacy of treatments and identifying those at risk.

Patients with insomnia also experience greater breaches in interpersonal relationships and general psychosocial upheaval.

Enlarge 

Health Care Costs

Insomnia causes a significant burden for the health care system and for employers in both direct and indirect expenses. People with insomnia often have reduced productivity due to absenteeism and decreased work efficiency. Many patients who report sleep problems also have reduced work satisfaction, attendance and job performance.

Health care and lost productivity costs have been consistently found to be greater in patients with moderate and severe insomnia compared with people without insomnia. In a retrospective study linking health claims data with a survey of members of a health plan in the Midwestern United States, mean total health care costs were 75% higher in the group with moderate and severe insomnia compared with those without insomnia ($1323 vs $757 respectively, P <0.05). Likewise, mean lost productivity costs were 72% higher in the moderate and severe insomnia group ($1739 vs $1013, P <0.001). Chronic psychiatric and medical comorbidities were positively associated with health care cost; but while the former were associated with lost productivity, the latter were not. In a cross-sectional telephone survey of 7248 workers across the United States, insomnia was found to be significantly associated (χ²₁ = 3.2; P <0.001) with decreased work performance due to presenteeism (lower performance despite being present in the workplace). On an individual level, the impact of insomnia was determined in this study to amount to 11.3 work days lost annually, or 7.8 days when controlling for comorbidities. On the national level, this amounts to an estimated 367.0 million days lost annually due to insomnia in the entire US workforce (252.7 million controlling for comorbidity). The total (direct and indirect) annual cost of insomnia in the United States has been estimated at between $28.1 billion and $216.6 billion.

It was also demonstrated that brief cognitive behavioral treatment for insomnia may be able to reduce health care utilization and costs. One study evaluated 84 outpatients who underwent cognitive behavioral treatment based on health care utilization indicators, such as estimated total and outpatient costs, estimated primary care visits, current procedural terminology (CPT) costs, number of office visits and number of medications. The study found that all utilization cost variables, except number of medications, significantly decreased (P-values <0.05) or trended towards a decrease at post-treatment. Those who completed the treatment had average decreases in CPT costs of $200 and estimated total costs of $75. Responders had average decreases in CPT costs of $210. No significant decreases occurred for those who did not complete treatment.

Development of Comorbid Disorders

Insomnia can increase vulnerability to the development of medical and psychiatric disorders such as hypertension, dyslipidemia, coagulation changes, depression, anxiety, substance abuse and can even decrease life expectancy. Although the pathophysiologic link between insomnia and comorbidities is unclear, insomnia is considered to be a disorder of chronic activation of stress responses, due to observations of hyperactivity of the central nervous system during sleep caused by the sympathetic arousal and activation of the hypothalamic pituitary adrenal axis (HPA axis). This activation is accompanied by increased heart rate, elevated blood pressure and elevated levels of pro-inflammatory cytokines and circulating catecholamines. The resulting hyperarousal is thought to be a factor in the cardiometabolic and psychologic abnormalities that often accompany insomnia.

Cardiovascular and Metabolic Abnormalities

Sleep apnea, insomnia, restless legs syndrome and other sleep disorders confer a heightened risk for cardiometabolic disease, particularly in the presence of reduced sleep duration. Short duration of sleep alone is associated with incident CVD risk. Individuals with insomnia have increased cortisol levels, metabolic rate and endothelial dysfunction, which are associated with higher CVD risk. In one study, reduced sleep duration was associated with obesity (odds ratio [OR]=1.18, P <0.0005), diabetes (OR=1.18, P <0.005), myocardial infarction (OR=1.36, P <0.0005), stroke (OR=1.22, P <0.05) and coronary artery disease (OR=1.59, P <0.0005). Effects for obesity, myocardial infarction and coronary artery disease were the most robust after adjustment for physical health.

Subclinical predictors of heart disease, such as coronary artery calcification, were found to be associated with shorter sleep durations over a 5-year period. A muting of the normal decrease in blood pressure following the transition from wakefulness to sleep, resulting in an increase in sleep-related blood pressure has been observed in patients with insomnia.

Persistent insomnia is also linked with a heightened risk for the future development of conditions such as hypertension, heart failure and diabetes (Figure 5-4, Figure 5-5, Figure 5-6).

Insomnia with short sleep duration is associated with increased risk of hypertension, to a degree comparable to that of other common sleep disorders, such as sleep-disordered breathing. In a cross-sectional study of 1741 patients, the highest risk of hypertension was seen in patients who slept <5 hours (OR=5.1) and those who slept 5 to 6 hours (OR=3.5) compared with normal sleepers and those who slept >6 hours (Figure 5-4). The risk for hypertension was significantly higher, but of lesser magnitude, in poor sleepers with short sleep duration.

Likewise, insomnia is associated with an increased risk of incident heart failure. A prospective study of people free from known heart failure at the start of the trial found that insomnia symptoms, such as difficulty initiating sleep, maintaining sleep almost every night, and non-restorative sleep quality more than once a week, were associated with an increased risk of incident heart failure. Patients who reported suffering from more symptoms were at higher risk of developing heart failure than those who had fewer symptoms (Figure 5-5).

Studies have found that chronic insomnia associated with objectively measured short sleep duration is a clinically significant risk factor for developing type 2 diabetes. Compared with normal sleepers and patients sleeping ≥6 hours, sleep, the highest risk of diabetes was in individuals with insomnia achieving ≤5 hours of sleep (OR=2.95) and in those who slept 5 to 6 hours (OR=2.07). Severe insomnia (complaint of insomnia for ≥1 year), with an objective sleep duration of <5 hours, was associated with a 300% higher odds for diabetes than the subjects who did not have a sleep complaint and slept for ≥6 hours (Figure 5-6). Objective measures of sleep duration in insomnia may be a useful marker of the biological severity and medical impact of the disorder.

Enlarge 

Enlarge 

Enlarge 

Psychiatric Disorders

There is a strong association between insomnia and current psychiatric conditions, particularly mood and anxiety disorders. Approximately 80% of patients suffering from major depressive disorder (MDD) report sleep-related complaints. These include trouble falling asleep, frequent nightly and early morning awakenings, nonrestorative sleep, short sleep duration, long sleep duration (hypersomnolence) and disturbing dreams. Close to 25% of patients with insomnia are affected by a mood disorder, whereas rates of depression are <1% in those without sleep complaints.

Insomnia in the context of major depressive disorder is also associated with significant added morbidity. In one study, depressive patients with suicidal ideation had poorer subjective sleep quality and duration scores than patients without suicidal ideation.

Longitudinal studies indicate that persistent insomnia is also associated with a heightened risk for the development of new mood, anxiety and substance abuse disorders. In one study, >1000 patients, ages 21 to 30 years, were followed over 3 years. In the patients with no psychiatric problems at the beginning of the study, those who started with insomnia had a substantially greater incidence of new major depression, anxiety disorders, substance abuse disorders and nicotine dependence by the end of the study (Figure 5-7). One meta-analysis of 13 studies found that insomnia increases the risk of several mental disorders, including anxiety (6 studies, OR=3.23), depression (10 studies, OR=2.83), alcohol abuse (2 studies OR=1.35), and psychosis (1 study, OR=1.28). In addition, insomnia is more likely to emerge prior to the onset of the acute phase of a mood disorder rather than during, or following, the emergence of the mood disorder.

Based on these interrelated relationships, there may be a bi-directional association between insomnia and psychiatric disorders.

Enlarge 

Mortality

Longitudinal studies have even linked insomnia to premature mortality. In a community-based prospective cohort study of 3430 patients, following a median follow-up period of nearly 16 years, it was noted that the relative risk for all-cause death in individuals with insomnia was considerably elevated and rose in proportion to the severity of the disorder; in severe insomnia, the relative risk was 1.70. A study in older adults with a mean follow-up of 12.8 years revealed that participants who had baseline sleep latencies of >30 minutes had a 2.14 times greater mortality risk and those with sleep efficiency <80% had a 1.93 times greater risk of death (Figure 5-8).

Several population-based studies have examined the association of sleep duration and/or insomnia complaints and increased risk of morbidity and mortality. Both long-sleep (i.e., >8 hours) and short-sleep (ie, <6 hours) durations were associated with increased morbidity and mortality. In contrast, an analysis of 39,139 participants in the Swedish National March Cohort found that insomnia was associated with higher mortality in individuals with a sleep duration of ≥9 hours (HR=2.98), but not those with a sleep duration <8 hours.

A study in a large US population sample found that, whereas there were significant associations between short sleep or long sleep and mortality in elderly subjects, there were no such relationships among middle-aged individuals. These results suggested that the relationship between sleep duration and mortality is largely influenced by death in elderly subjects and by the measurement of sleep durations closely before death. Inconsistent results have been observed in prospective studies of middle-aged adults in the United States. While significant associations between insomnia complaints and various medical problems were observed, insomnia complaints were not associated with an increased risk of death over 6.3 years. Furthermore, there was no association between the use of hypnotics and increased risk of mortality. However, a prospective cohort study found that during 20 years of follow-up, regular use of hypnotics was associated with a significantly increased risk of all-cause mortality. A meta-analysis of 17 studies, comprising more than 36 million individuals, found no evidence of increased mortality in patients with frequent (>3 times per week) and ongoing (>1 month) insomnia symptoms (OR=1.06). Variable definitions, follow-up time and consideration of risk factors may be the cause of these inconsistencies. Clearly, more research is required in this area.

Enlarge 

Conclusion

Insomnia is a chronic condition with significant associated risks and often leads to daily functional and cognitive impairments. If severe and allowed to persist, insomnia increases the risk for the development of comorbid medical and psychiatric conditions, such as major depression, anxiety and substance use disorders, hypertension, heart failure, diabetes and even increased mortality. The relationships between underlying mechanisms of hyperarousal and the development of comorbidities require further investigation. In addition, the question of whether these comorbidities can be mitigated or prevented through the effective management of insomnia is an open, yet intriguing, question.