Chapter 135 Insomnia in Older Adults

Abstract

Insomnia is a complaint of difficulty initiating or maintaining sleep or of nonrestorative sleep resulting in significant daytime consequences. Chronic insomnia is prevalent in about 10% of the adult population; however, increasing age is a risk factor for the development of insomnia, especially in women. Although late-life insomnia is usually attributed to medical and psychiatric morbidity rather than to age-related changes per se, underlying age-related physiologic changes in sleep–wake regulation—circadian rhythms and sleep homeostasis—have been identified. Other factors associated with insomnia in the elderly include medications or other substances and primary sleep disorders. Key elements in appropriate evaluation and management include considering the type of insomnia complaint and assessing sleep patterns, including daytime napping, daytime consequences, and comorbidity. Behavioral treatment should be considered first, and when necessary, the newer hypnotic medications may be added.

Insomnia is a complaint of difficulty initiating sleep, difficulty maintaining sleep, or experience of nonrestorative sleep occurring at least three times a week and lasting at least 1 month.¹ Typically, insomnia may be a chronic condition lasting for several years. In the elderly population, a chronic insomnia complaint is common, and it is often related to medical or psychiatric comorbidity. Owing to the widespread notion that insomnia is an inevitable consequence of aging, it is often not recognized or properly treated. However, growing evidence suggests that insomnia is not only a symptom consequent to morbidity but also a potential contributor to subsequent morbidity.² Thus, increasing the awareness of clinicians and older adults regarding the significance of identifying and managing insomnia is imperative for improving sleep and health in this population.

Epidemiology and Risk Factors

The prevalence rate of insomnia increases with age, and it has been shown to be higher in women.³ In a sample of more than 5000 adults from the Sleep Heart Health Study (SHHS), older age was significantly related to poor sleep in men, particularly reduction in slow-wave sleep and increased stages 1 and 2, whereas in women, older age was related to subjective sleep complaints.⁴

It has been suggested that when categorizing studies based on the definition of insomnia used, studies focusing on symptoms of insomnia have shown an increased prevalence with age, and studies focusing on global sleep dissatisfaction and on the Diagnostic and Statistical Manual of Mental Disorders, 4th edition, text revision (DSM-IV-TR) diagnosis for insomnia were not age dependant.⁵ This hypothesis is supported by a study of more than 13,500 participants aged 47 to 69 years, assessing the prevalence of three major insomnia complaints and their correlates.³ Twenty-two percent of the sample complained of difficulty falling asleep, 39% complained of difficulty staying asleep, and 35% complained of nonrestorative sleep. In a multivariate analysis, increasing age was significantly associated only with a complaint of difficulty staying asleep, whereas depression and heart disease were associated with all three complaints. Other factors related to the sleep complaints were medical illnesses, lower socioeconomic status and education, and unhealthy behavior such as current or former alcohol use and cigarette smoking.

Other studies have also examined insomnia in the elderly population. In a sample of more than 9000 participants aged 65 years and older from the National Institute of Aging’s Established Populations of Epidemiological Studies of the Elderly (EPESE), more than 50% reported at least one sleep complaint, and 35% to 40% reported disorders of initiating or maintaining sleep (or both) on a chronic basis.⁶ In a 3-year follow-up of this sample, an annual incidence rate of 5% was reported.⁷ Incidence rates were highest in those with chronic medical conditions such as heart disease, stroke, and diabetes. Remission occurred in nearly half of those with insomnia at baseline, and it was related to improvements in perceived health. Similarly, in a representative sample of general practice patients aged 65 years and older, the annual incidence rate for late-life insomnia was 3.1%.⁸ Significant and independent risk factors in this sample were depressed mood, poor physical health, and intermediate to low physical activity.

Based on the National Sleep Foundation survey from 2003, depression, heart disease, bodily pain, and memory problems were the disorders most commonly associated with insomnia.⁹ In fact, in studies using rigorous exclusion criteria for comorbidities, prevalence of insomnia is very low in healthy older adults. These findings lend further support to the epidemiologic evidence demonstrating that the bulk of geriatric sleep complaints and disorders is not the result of age per se, but rather co-segregates with medical and psychiatric disorders and related health burdens and even gender.¹⁰^,^10a

One problem with insomnia in the elderly is that it is often unrecognized by physicians. In a study of older adults in primary care practices in the midwest United States, 69% of patients endorsed at least one sleep problem, 40% endorsed at least two sleep problems, and 45% endorsed symptoms of insomnia, but these complaints were identified in the medical charts only 19% of the time.¹¹ In this same study, the two questions that best identified those with poor sleep at risk for medical and psychiatric problems were “Do you feel excessively sleepy during the day?” and “Do you have difficulty falling asleep, staying asleep, or being able to sleep?” These two questions would be easy for physicians to integrate into their standard history.

Consequences of Insomnia

The reason it is so important to identify insomnia in older adults is that poor sleep can result in serious consequences. Studies have assessed the health consequences of insomnia as well as the effect of insomnia on physical functioning and performance. In a study of several thousand older men, lighter and more fragmented sleep were associated with poorer performance, particularly in age-adjusted models. Shorter total sleep time, sleep efficiency below 80%, and more than 90 minutes of wake time were associated with lower grip strength, slower walking speed, inability to stand from a chair without assistance, and inability to complete a narrow walk course.¹²

Results of multiple surveys have shown that insomnia in adults can result in decreased cognitive performance, such as difficulty sustaining attention, slowed response time, and memory problems. In a controlled laboratory study comparing patients with insomnia and good sleepers, performance impairments such as decreased vigilance, working memory, and motor control, as well as mood disturbances, concentration difficulties, and fatigue were evident in the insomnia group.¹³ Changes in cognition are of particular concern in the elderly population, where cognitive decline depends on age and may be an early sign of dementia.¹⁴ In a 2-year prospective study assessing relationships between snoring, sleep duration, and sleep difficulties with cognitive functioning in elderly women, short sleep duration (≤5 hours) and insomnia complaints were related to lower scores on cognitive tests at baseline but not at 2-year follow-up.¹⁵ In a 3-year longitudinal study, chronic insomnia was found to be an independent risk factor for cognitive decline in older men but not in older women,¹⁶ suggesting that cognitive decline in insomnia might correlate with sex. Alternatively, daytime sleepiness may be the underlying factor for cognitive decline, rather than insomnia. In a longitudinal study, daytime sleepiness, but not insomnia, was related to incident dementia and cognitive decline in men.¹⁷

On the other hand, in the Study of Osteoporotic Fractures (SOF), cognitive decline in close to 3000 elderly women age 70 years and older was associated with poor sleep based on actigraphically measured sleep efficiency of 70% or less, long sleep latency, and increased wake after sleep onset.¹⁸ In a study of more than 1000 older men and women, cognitive impairment was associated with short sleep duration of less than 6 hours and daytime nap of longer than 1 hour.¹⁹

Additionally, studies on the consequences of insomnia have identified reduced measures of health-related quality of life (HR-QOL), increased psychological distress, lower medical status and increased utilization of health services.²⁰^–²² Further consequences are related to reduced professional performances, such as increased absenteeism, decreased work performance, increased risk for road accidents, poor self-esteem, and less job satisfaction.²³

Several studies have found that poor sleep is associated with increased risk of falls, even after controlling for relevant factors including benzodiazepine use.²⁴^,²⁵ In the SOF study, less than 5 hours of sleep per night and sleep efficiency of 70% or less were independent risk factors for falls in elderly women, but use of benzodiazepines did not increase the risk.²⁵

Insomnia also increases the risk of mortality. In a study of older adults followed for close to 5 years, those with initial sleep latencies of longer than 30 minutes or sleep efficiency less than 80% had close to twice the risk for mortality.²⁶ Similar results were found in the SOF study of older women. After adjusting for clinical and demographic factors, subjects who slept less than 5 hours a night and who had a sleep efficiency less than 65% or who napped for more than 2 hours a day had an increased risk of mortality at follow-up.²⁷

For these reasons, it is imperative for physicians to be able to recognize and treat insomnia in older adults.

Etiology

Underlying factors involved in the development of late-life insomnia include age-related changes in homeostatic and circadian sleep–wake regulation, psychiatric and medical comorbidities, medications and other substances, and primary sleep disorders. Evidence for each of these factors is reviewed separately.

Age-Related Changes in Sleep Regulation

Developmental changes in sleep in the elderly are characterized by advanced sleep phase, including earlier bedtimes and earlier wake times, reduced sleep consolidation, and altered sleep architecture, indicating a transition to lighter sleep. To understand the basis for these changes, it is necessary to understand some of the basic mechanisms of human sleep regulation.

Sleep regulation is based on an interaction between the homeostatic pressure for sleep and the output of the circadian pacemaker. Homeostatic sleep pressure reflects the increasing need for sleep that accumulates during the waking hours and dissipates during sleep, as marked by increased EEG slow waves at the beginning of the nocturnal sleep episode, which gradually decrease throughout the night. The endogenous circadian pacemaker located in the suprachiasmatic nucleus (SCN) of the hypothalamus regulates the synchronous timing of several physiologic variables including hormone secretion, core body temperature, and sleep–wake states. Regulation of the timing of sleep and wake states is achieved by promoting a signal of increased wakefulness throughout the day and a signal of increased sleep consolidation throughout the night.²⁸^,²⁹ In young adults, daytime wakefulness and nighttime sleep consolidation are high due to both of these bioregulatory mechanisms.

However, both homeostatic and circadian mechanisms change with age. Advanced age has been associated with a marked reduction in slow-wave sleep (SWS) and an increase in lighter sleep. This reduction in SWS indicates weaker homeostatic sleep pressure in the elderly.³⁰

Under entrained conditions, timing of the circadian rhythm of core body temperature and habitual wake times are advanced to an earlier hour in the elderly, and the amplitude of the circadian rhythm of core body temperature is decreased, indicating a reduced circadian signal promoting sleep in the early morning hours.³¹ The circadian signal for wakefulness is also reduced,³² as reflected in sleep episodes and reports of sleepiness in the early evening hours.

In summary, reductions in both the homeostatic drive for sleep and in the strength of the circadian signal for sleep in the early morning hours and for wakefulness in the early evening hours have been implicated as underlying factors for reduced sleep consolidation, advanced sleep phase, and early-morning awakenings in the elderly.

Medical and Psychiatric Comorbidities

Many chronic medical conditions and illnesses are known to disrupt sleep. These include arthritis, angina pectoris, congestive heart failure, coronary artery disease, chronic obstructive pulmonary disease, end-stage renal disease, diabetes, asthma, stroke, gastroesophageal reflux disease, dementia and Alzheimer’s disease, Parkinson’s disease, cancer, and menopause. In a study of more than 1000 older adults aged 60 to 101 years, poor health was associated with short sleep duration, long sleep latency (longer than 80 minutes) and going to bed late and waking early.¹⁹ In a large survey of older adults, those with heart disease, lung disease, stroke, or depression were more likely to report difficulties with sleep. In addition, the more medical conditions subjects reported, the worse the sleep complaint and the more likely subjects were to rate their sleep as poor.⁹ In a group of older adults who are likely to have multiple medical or psychiatric conditions, poor sleep is a likely comorbid condition.

In a study examining sleep and health in 1500 adults older than 60 years in 11 primary care offices, complaints of poor sleep and excessive daytime sleepiness were significantly associated with both poor physical and poor mental health–related quality of life.¹¹ Other studies have also shown an association between poor mental health, especially depression and anxiety, and late-life insomnia.⁶^,³³

Insomnia has also been implicated as a risk factor for heart disease,³⁴ although the mechanism mediating this relationship is yet to be determined. The authors hypothesized that insomnia may be part of a larger syndrome including poor health and depression, or it may be a marker of chronic stress and autonomic dysfunction. Collectively, the evidence indicates that insomnia may be a cause or a consequence of comorbidity. Thus, comorbid insomnia has been suggested as the more appropriate term.³⁵ Such a distinction has important implications not only in determining causal relationships between insomnia and comorbidity but also for considering treatment strategies. Treatment and management should focus not only on comorbid illnesses but also on insomnia as a distinct entity.

Medications and Substances

Polypharmacy is a serious problem in older adults, and the use of multiple medications also contributes to insomnia. Prescription medications known to be related to insomnia include antidepressants, such as bupropion, selective serotonin reuptake inhibitors (SSRIs), monoamine oxidase inhibitors (MAOs), and tricyclic antidepressants (TCAs) except for amitriptyline and venlafaxine.³⁶ Other medications prescribed for medical conditions that are associated with insomnia include bronchodilators, beta-blockers, central nervous system (CNS) stimulants, gastrointestinal drugs, and cardiovascular drugs. Concomitant use of several types of medication (polypharmacy) further increases the risk of sleep disturbances in this age group. Adjustment of the timing and dosing and the contraindications between medications in elderly persons can lead to improvements in their sleep.³⁶

Moderate alcohol consumption in elderly persons has been related to sleep disturbances including insomnia and sleep-disordered breathing (SDB).³⁷ Other substances known to be related to insomnia include caffeine and nicotine. Although the effects of these substances are yet to be investigated in the elderly population, it is unlikely that they would not also disrupt sleep in the elderly.

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