In this study, 1 in 5 participants, representing 44.3 million civilian, noninstitutionalized US adults, has arthritis diagnosed by a doctor, and by 2030, the number of people affected is projected to increase by 40% (22
). Arthritis may substantially reduce the quality of sleep with multiple consequences. Our study of a recent nationally representative sample demonstrated that adults with arthritis have a higher prevalence of sleep disturbances than individuals without arthritis, with insomnia affecting 10.2 million adults with arthritis. Joint pain and physical limitation due to pain were identified as important mediators, indicating that the presence of symptoms was a more important correlate of sleep disturbance than the diagnostic label of arthritis.
Our results are consistent with previous studies that reported that sleep disturbances are prevalent among patients with arthritis (6
). Most studies included small samples and were focused on inflammatory arthritis, which represents a small proportion of the population with arthritis. Studies of patients with osteoarthritis showed that sleep problems were also common among these patients and correlated with pain, poor physical functioning, depression, or less social support (24
). In the Johnston County Osteoarthritis project, patients with hip or knee osteoarthritis were 3 times more likely to report sleep problems than people without osteoarthritis (26
). We used an epidemiologic approach to extend these observations to the national population level. Because our survey-based sample was representative of the US population, the majority of participants with arthritis in our study likely had noninflammatory arthritis (19
). A significant association was found between arthritis and all 3 types of sleep disturbance.
Several sociodemographic characteristics and health behaviors were independently associated with sleep disturbance, including age, female sex, white race, less social support (divorced or never married), lower education level, employment status (formerly or never worked), current smoking, and alcohol use. In addition, chronic diseases such as hypertension, heart and lung disease, and upper GI problems were associated with one or more sleep quality problems. These findings are consistent with other epidemiologic studies on representative community-dwelling populations, which also reported that sleep disturbances are more common in women, older people, and persons of lower socioeconomic status (11
). Furthermore, previous studies have reported that patients with COPD or cardiovascular or cerebrovascular diseases have an increased risk of sleep disorders (19
). We examined not only the relative odds of sleep disturbances associated with comorbid conditions, but also adjusted prevalences of sleep disturbances in adults with chronic diseases other than arthritis. These adjusted prevalences were generally similar to those of persons with arthritis, indicating that although arthritis is associated with an increased risk of sleep disturbances relative to those without arthritis (including those with no chronic diseases), many chronic diseases are associated with an increased risk of sleep disturbances. This comparison places the arthritis associations in context and provides a clearer understanding of the role of chronic diseases in sleep disturbances.
Depression and anxiety were strongly associated with sleep disturbances. Adults with depression or anxiety were 3 times more likely to report sleep problems than those without depression or anxiety. Similar associations of mood disorders with sleep quality have been previously demonstrated in patients with inflammatory arthritis or osteoarthritis (11
), in patients with psychiatric and other chronic diseases (32
), and in the general population (34
). Although the cross-sectional nature of our study precludes making causal inferences, a bidirectional relationship likely exists between sleep disturbance and depression (35
). In addition, our study provides new information about subgroups of adults with arthritis most at risk for sleep problems. Depression and anxiety were the most important factors identifying subsets of individuals with arthritis affected with all 3 sleep disturbances. Among adults with arthritis but without anxiety or depression, those with upper GI problems had a higher risk of sleep difficulties. This finding has clinical importance, since many medications used for arthritis pain relief can have upper GI symptoms as adverse effects (37
). Appropriate use of these medications may limit secondary consequences of worsening sleep.
We found that joint pain and limitation due to joint pain were important mediators of sleep disturbance. Significant associations between sleep disturbance and pain or limitation due to pain have been described in inflammatory arthritis or osteoarthritis (7
), as well as in patients with chronic pain but without arthritis (38
). A recent survey demonstrated that sleep disturbance in patients with RA was linked to pain, mood, and disease activity (8
). The 2000/2001 Canadian Community Health Survey reported that a substantial amount of the relationship between arthritis and sleep problems was mediated by pain (11
). In addition, pain was a significant predictor of insomnia in a large survey of the Canadian population (40
). Pain can disrupt sleep, and poor sleep may increase pain intensity (41
). Elevation of plasma proinflammatory cytokine levels, especially tumor necrosis factor α
) and interleukin-6, has been detected in patients with disorders of excessive daytime sleepiness (42
). Sleep problems have received increased attention with the recent observation that anti-TNFα
treatment may improve sleep and alertness disturbances (43
). This increased attention is manifested by inclusion of measures of sleep quality as outcome measures in clinical trials of patients with arthritis (44
The causes of sleep difficulties in patients with arthritis are likely multifactorial, and treatment may require a multidisciplinary approach. However, only 30% of older Americans with sleep disturbance seek medical care for this problem, relying instead on various self-care strategies (3
). Patients with arthritis should be encouraged to report sleep quality problems. In the 2005 Sleep in America Poll, only 29% of participants had ever been asked by their doctors about their sleep problems (12
). Treatment, including cognitive– behavioral therapy, exercise, or complementary methods, may improve both joint pain and sleep quality (47
The strengths of this study include the large nationally representative sample, with a response rate of 78%. We examined 3 different sleep disturbances to have a broad representation of sleep problems. In contrast to other studies where the cause of pain was not described, we included data focused on joint pain, as well as limitations due to joint pain. We also provided new information about the prevalence of sleep disturbances in persons with arthritis in comparison to those with other chronic diseases, and identified subgroups of individuals with arthritis most at risk for sleep disturbances. There are some limitations in this study. The assessment of sleep disturbances was based on symptoms, rather than using methods such as polysomnography, because diaries or questionnaires are the only feasible way to assess sleep quality in large national samples. Survey data did not allow us to classify insomnia using diagnostic criteria (49
). Data were also not available to evaluate the duration or severity of insomnia or to differentiate primary and secondary causes of insomnia. Reports of sleep duration may not be accurate, but differential reporting would not be expected between persons with and without arthritis. Data on physician-diagnosed arthritis were also self-reported, but self-reports have been validated previously for surveillance purposes (17
). Although certain medications, notably opioid analgesics, which may be used by persons with severe arthritis, can affect sleep, information on medication use was not included in the survey. Finally, because the study was cross-sectional, we could not ascertain the direction of causality between sleep difficulties and pain or depression.
Our results suggest that adults with arthritis are significantly more likely to develop insomnia, excessive daytime sleepiness, or short sleep duration than those without arthritis, and that this difference is mainly related to joint pain and limitation due to pain. These findings suggest that improvement in joint pain may decrease sleep problems. Among individuals with arthritis, those with anxiety and depression are mostly affected by sleep disturbances. Physicians and other health care providers should be aware of these often neglected symptoms. Patients with arthritis, especially those reporting pain or with depression or anxiety, should be regularly screened for sleep quality problems and have the causes of sleep problems treated appropriately.