Management of Insomnia: Considerations For Patients With Chronic Pain
Sleep is a vital physiologic process, and notable reductions in sleep can have negative physiologic, cognitive, and emotional effects.1 Primary insomnia is estimated to occur in 1% to 10% of the general adult population and in up to 25% in older adults.2 Many patients who suffer from insomnia have impairments in their quality of life as a result of decreased energy, difficulty concentrating, memory impairment, and increased fatigue.2,3 The incidence of insomnia among patients with chronic pain is significantly higher than that in the general population.4 According to data from the National Sleep Foundation, about two-thirds of patients with chronic pain report problems with sleep.
Types of Insomnia
Currently, classifications for insomnia are available in two references, the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) and the International Classification of Sleep Disorders, Second Edition (ICSD-2).2,5 Both identify various subtypes of insomnia, with the DSM-IV classifying insomnia as either a primary disorder or secondary to some underlying cause. The ICSD-2 classifies insomnia into various categories; however, these specific categories are beyond the scope of this review.5 Insomnia is further classified based on its duration, with transient insomnia generally classified as symptoms lasting only a few (1-3) days, acute insomnia occurring when symptoms last 3 days to less than 4 weeks, and chronic insomnia occurring when symptoms last more than 4 weeks.6
According to the DSM-IV, patients with primary insomnia complain of difficulty initiating or maintaining sleep or nonrestorative sleep for at least 1 month; the specific diagnostic criteria are summarized in Table 1.2 Nonrestorative sleep is characterized as sleep that is restless, light, or of poor quality.
There are numerous secondary causes of insomnia ranging from underlying mental disorders, other general medical conditions, or those that are related to a substance or medication.6,7 Patients with chronic pain syndrome or degenerative diseases may have trouble sleeping because of their pain. Examples of chronic pain syndromes associated with insomnia include fibromyalgia, arthritis, back pain, and headaches.4,8
The relationship between pain and difficulty sleeping is complex and has been described as a vicious cycle.4,9,10 Pain intensity has been shown to increase the severity of sleep disturbances, and vice versa.10 Pain-related arousal has been shown to differ from somatic and cognitive arousal.9 In addition, pain is associated with development of depression and anxiety, which can contribute to sleep difficulties and insomnia.
Insomnia also can be drug induced, especially by substances that result in central nervous system (CNS) stimulation. A list of medications and substances that may adversely affect sleep are summarized in Table 2.4,6,7,9
In a National Institutes of Health (NIH) statement on insomnia, various risk factors for insomnia were highlighted.11 The first was age, with rates of insomnia increasing in older patients. This primarily has been attributed to the high prevalence of medical and psychosocial conditions in this patient population, coupled with the frequent use of polypharmacy to treat these conditions.12 Higher rates of insomnia in this patient population also may be a result of older patients having a substantial decline in their arousal threshold (the mechanism that preserves sleep) compared with younger patients.13 Data suggest that older patients are more easily awakened by external noises such as traffic because of diminished sleep intensity.
The NIH also noted that women have a higher prevalence of insomnia, particularly in the postmenopausal years.11 These higher rates have been attributed to a multitude of factors, such as more frequent occurrence of depression and anxiety in women compared with men, insomnia related to pregnancy, and sleep disorders occurring during the menopausal transition period.14 Other NIH-identified groups who have a higher prevalence of insomnia include patients with lower education and income and those who are divorced, separated, or widowed.11 Currently, the data for differences in insomnia rates among various racial or ethnic groups are inconclusive.
A 2008 Clinical Guideline for the Evaluation and Management of Chronic Insomnia provides recommendations for the assessment and treatment of patients with insomnia.7 Patients presenting with insomnia should have a detailed history taken to identify any medical, psychiatric, or substance-related factors that may be contributing to their insomnia. In addition, a thorough sleep history should be obtained. Some elements of the sleep history include characterization of the primary complaint (eg, difficulty falling asleep vs awakenings vs poor sleep), frequency and duration of insomnia, identification of nocturnal symptoms, impact on daytime activities and functioning, and any past or current treatments and responses. A physical exam also is recommended to identify risk factors for other sleeping disorders (eg, sleep apnea), such as obesity, increased neck circumference, and upper airway anatomical changes. At minimum, the guideline recommends that clinicians perform the general medical assessment as described above in addition to having patients complete a sleep questionnaire and a 2-week sleep log/diary to help identify sleep patterns. An example of a sleep questionnaire is the Insomnia Severity Index, a 7-item rating to assess patients’ perceptions of insomnia.
In patients experiencing pain or those with chronic pain, careful assessment is required in order to determine how well the pain itself is being managed.9 The presence of comorbid psychiatric disorders also should be considered. As previously mentioned, depression and anxiety are common in patients with chronic pain and may further exacerbate sleep disturbances and insomnia.
Treatment of Insomnia
Insomnia should be treated when the condition affects daytime functioning, the patient’s overall health, or sleep quality.7 The first step for treatment is the identification and management of comorbid conditions that are associated with insomnia, such as depression or chronic pain, followed by the modification of behaviors or medications (see Table 2) that can worsen insomnia. If medications that are associated with insomnia cannot be discontinued or switched, consideration should be given to adjusting the timing of administration. The main goals for treating insomnia include improving sleep time and/or quality and reducing daytime impairments. The recommended treatment approach involves pharmacologic and nonpharmacologic interventions.