Prevalence of Sleep Disturbance in Adults
The study examined the prevalence and relationship between sleep disturbance and chronic pain. Research questions were: (1) What is the prevalence of sleep disturbance in adults with chronic pain, and how does this prevalence compare with healthy and insomniac adults? (2) What is the relationship between sleep disturbance and chronic pain? (3) What is the relationship of patient characteristics to sleep? This descriptive, correlational field study was done at an interdisciplinary pain clinic, sampling 99 adults, and using an 11-point pain scale and a visual analog sleep scale. For every disturbance item, more than 47% of subjects reported a score of 50 or higher, twice as high as those for healthy adults, indicating disrupted sleep. For every effectiveness item, more than 54% of subjects reported a score of 50 or less, significantly lower than for healthy adults, indicating poor sleep quality. For every supplementation item, more than 60% reported mean scores of 10 or less, indicating minimal napping, yet scores were higher than for healthy adults. For all three scales, scores were similar to the mean scores for insomniacs. Soundness of sleep showed a small but significant positive (r <.30) correlation with years of pain. Supplementation scale items were not correlated with either years of pain or pain intensity. Fragmentation was significant on the basis of gender, with men having higher scores than women. Age was a negative predictor of sleep latency. Education and age were negative predictors of the quality of sleep.

Millions of people suffer from chronic or intractable pain (American Academy of Pain Medicine, 2000). Chronic pain can have a multidimensional effect on the individual leading to problems with impaired emotional, behavioral, and functional abilities (Burckhardt, Clark, O´Reilly, & Bennett, 1997; Friedman, Leadley, Stickney, & Austin, 1995; Greene, Johnson, & Maricic, 1993). Chronic pain has a major financial impact on our society, resulting in lost work days, increased workers´ compensation expenses, use of sick days, and expenditures on traditional and nontraditional health care remedies (Friedman et al., 1995; Ingemarsson, Sivak, & Nordholm, 1996).

Sleep disturbance has long been associated with chronic pain, though the nature of the sleep disturbance has varied by study and population (Ahmedzai & Brooks, 1997; Boissonnault & Di Fabio, 1996; Burckhardt et al., 1997; Friedman et al., 1995; Hammack et al., 1996; Haythornthwaite, Hegel, & Kerns, 1991; Hyyppa & Kronholm, 1995; Jones, Koh, Steiner, Garrett, & Calin, 1995; Kucukdeveci, Tennant, Hardo, & Chamberlain, 1996; Lavin, Pappagallo, & Kuhlemeier, 1997; Lehtinen et al., 1996; Morriss, Wearden, & Battersby, 1997; Passcheir, deBoo, Quaak, & Brienen, 1996; Perlis et al., 1997; Stone, Broderick, Porter, & Kaell, 1997; Tishler, Barak, Paran, & Yaron, 1997; Vines, Cox, Nicoll, & Garrett, 1996). Populations with pain in whom sleep disturbances have been documented include adults with headaches, fibromyalgia, chronic fatigue syndrome, rheumatoid arthritis, ankylosing spondylitis, osteoarthritis, carpel tunnel syndrome, back pain, and Sjogren´s syndrome (Ahmedzai et al., 1997; Boissonnault et al., 1996; Hammack et al., 1996; Jones et al., 1995; Kucukdeveci et al., 1996; Passcheir et al., 1996; Perlis et al., 1997; Tishler et al., 1997). However, the precise nature of the sleep disturbance remains unclear. Sleep disturbances associated with chronic pain vary across populations, and include difficulty falling asleep, difficulty staying asleep, early awakening, and interrupted sleep.

Sleep contains three different components: disturbance, effectiveness, and supplementation. Disturbance includes interruptions to sleep and difficulty falling asleep. Disturbance can thus be attributed to fragmentation of sleep (i.e., mid-sleep awakening) and to latency (i.e., amount of time it took to fall asleep). The effectiveness of sleep refers to quality and length of sleep. Quality as a component of sleep contains such concepts as feeling rested upon awakening and the total number of hours of sleep obtained while in bed. Supplementation of sleep consists of augmentation of sleep through napping during the day (i.e., morning/afternoon naps).

Studies of inpatients with pain and of volunteers with chronic pain in sleep laboratories have revealed different patterns of sleep disturbance (Dinges et al., 1997; Lehtinen et al., 1996; Lobbezoo, Thon, Remillard, Montplaisir, & Lavigne, 1996; Perlis et al., 1997). Multiple types of sleep disturbances were documented for one group of chronic pain inpatients who slept approximately 5 hours per night, woke from pain one to two times per night, and had difficulty initiating and falling back to sleep (Haythornthwaite et al., 1991). Very light sleep was documented in fibromyalgia participants, who were aroused easily as a result of external stimuli (Perlis et al., 1997). Participants with chronic diseases in a rehabilitation facility who complained of poor sleep patterns had increased night motor activity and daytime fatigue and somnolence (Hyyppa et al., 1995). No relationship was found between increasing cervical dystonia and sleep disturbance, but improving sleep in these participants led to improved symptomatology (Lobbezoo et al., 1996).

Outpatient studies of adults with chronic pain revealed similar findings relative to sleep. Participants with perceived poor sleep reported higher levels of pain and fatigue than did persons who reported good sleep (Boissonnault et al., 1996; Hyyppa et al., 1995; Kucukdeveci et al., 1996; Stone et al., 1997). If fatigue was a presenting symptom, 41% of individuals were more likely to wake up three or more times during the night (Jones et al., 1995). Participants with chronic headaches were found to have decreased energy, sleep deprivation, and social isolation when compared with healthy controls (Passcheir et al., 1996).

The true relationship between sleep disturbances and pain remains unknown (Haythornthwaite et al., 1991; Jones et al., 1995; Lobbezoo et al., 1996; Morriss et al., 1997; Perlis et al., 1997; Stone et al., 1997; Tishler et al., 1997; Vines et al., 1996). A linear relationship has been proposed, associating increases in pain with increasing insomnia, but this relationship has not been documented. Neither pain nor sleep is a simple construct, and multiple variables have been explored as a part of this complex relationship. In healthy adults, sleep deprivation resulted in a range of somatic, cognitive, and emotional disturbances, including neurobehavioral markers such as mood disturbance and lack of performance, but these relationships were not linear (Dinges et al., 1997). Depression may potentiate pain and sleep disturbances, though that relationship is neither consistent nor linear. Individuals who already suffer from chronic pain also suffer from secondary psychological components not directly related to the source of the pain (Greene et al., 1993). These may include depression, anxiety, panic disorders, and other psychiatric diagnoses, which worsen their present condition but not in a linear manner (Burckhardt et al., 1997; Friedman et al., 1995; Haythornthwaite et al., 1991; Kucukdeveci et al., 1996; Morriss et al., 1997; Passcheir et al., 1996; Tishler et al., 1997). Psychiatric disorders were not a contributing variable to the sleep disturbances experienced by participants with chronic fatigue syndrome (Morriss et al., 1997).

Because the relationship between pain and sleep is not well understood (Lavigne et al., 2000) , the framework explicating the relationship among pain, sleep, and other concepts is probably both recursive and complex, as illustrated in Figure 1. Chronic pain may be thought of as a stressor that activates and maintains areas within the central nervous system responsible for the awake state, while dampening areas responsible for the initiation and maintenance of sleep, so that sleep disturbances escalate as pain escalates. Lack of the reparative or restorative functions of sleep may impair healing, leading to pain directly. Lack of sleep may also affect central nervous system areas responsible for mobilizing coping mechanisms, which are useful for dampening the pain experience. Sleep disturbances would then lead directly to more pain, and indirectly to a heightening of the pain experience through impairment of usual adaptive mechanisms. The exact nature of the sleep disturbances experienced by adults with chronic pain is important to establish as a first step in understanding the nature of the relationship between sleep and pain. Evidence of the nature of the relationship between chronic pain and sleep disturbance would be helpful in understanding how these concepts interact and lead to significant cost and suffering.



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Conceptual framework showing the positive, recursive relationships among pain, central nervous system arousal, and sleeplessness.





Therefore, the purpose of this study was to determine the prevalence of sleep pattern disturbances in adults receiving chronic pain clinic services compared with healthy adults and insomniac adults, and to determine the relationship between chronic pain intensity and sleep disturbances. In addition, this study also investigated the relationships between several patient characteristics (i.e., age, gender, income, education, and number of dependents) and sleep disturbance.