Measures of sleep in rheumatologic diseases: Epworth Sleepiness Scale (ESS), Functional Outcome of Sleep Questionnaire (FOSQ), Insomnia Severity Index (ISI), and Pittsburgh Sleep Quality Index (PSQI)

Abstract

Fatigue is a major symptom associated with rheumatologic diseases such as systemic lupus erythematosis and rheumatoid arthritis and may be a direct manifestation of disease activity, but such fatigue may also be related to sleep disturbances (1, 2). Indeed, sleep disturbances are common in a variety of rheumatologic diseases (3–5). Such disturbed sleep may be due to pain, depression, lack of exercise, or corticosteroid usage (6–8). Sleep quality may also be impaired by comorbid sleep disorders, such as obstructive sleep apnea or restless leg syndrome, the prevalences of which are reported to be high in rheumatologic populations (9–12). Sleep disturbances may, in turn, impact functional disability, lower pain thresholds, or impair immune function and thus contribute to rheumatologic-associated morbidities (13–15). Sleep disturbances in fibromyalgia and rheumatoid arthritis have received relatively more attention than in other rheumatologic diseases, but even in fibromyalgia and rheumatoid arthritis, there are many unanswered questions related to the causes and outcomes of sleep disturbances (3). The study of sleep disturbances can be onerous because gold standard direct tests, such as polysomnography and multiple sleep latency testing, are both expensive and require considerable commitment of time from research subjects. Laboratory-based sleep studies may present an additional challenge in rheumatologic populations in whom mobility restriction and pain may significantly increase subject burden. Thus, there is strong impetus for utilizing patient-reported measures in assessing sleep and sleep-related outcomes in rheumatologic diseases. Four patient-reported measures are discussed in this section, each of which captures a different sleep-related domain and has been extensively utilized in a variety of populations: [1] the Epworth Sleepiness Scale, which assesses daytime sleepiness, [2] the Functional Outcome of Sleep Questionnaire, which assesses sleep-related quality of life, [3] the Insomnia Severity Index, which measures the subjective symptoms and consequences of difficulties initiating and maintaining sleep, and [4] the Pittsburgh Sleep Quality Index, which assesses perceived sleep quality more generally. Please note that the Medical Outcomes Study Sleep Scale, a global measure of sleep quality and sleep-related outcomes, is discussed separately in this issue of Arthritis Care & Research, within the section on fibromyalgia. None of the scales reviewed here was developed specifically for rheumatologic or musculoskeletal conditions and, indeed, each has relied heavily for validation on populations with primary sleep disorders. To varying extents, as discussed below, each of these measures has been used in rheumatologic populations. Nonetheless, clinicians and researchers must carefully consider their objectives and the appropriateness of their populations in selecting a sleep questionnaire to meet their needs.