Polysomnographic and health-related quality of life correlates of restless legs syndrome in the Sleep Heart Health Study.

IT IS NOT CLEAR WHETHER RESTLESS LEGS SYNDROME (RLS) SHOULD BE CONSIDERED A SLEEP DISORDER. ON THE ONE HAND, RLS IS USUALLY DESCRIBED as a sensorimotor neurological disorder, and in fact there are no sleep related symptoms in the established diagnostic criteria for RLS.1 However, sleep disturbance is the primary clinical morbidity of RLS,2 and it may also mediate other important secondary features of the disorder such as reduced quality of life,3 depressive symptoms,4 and cardiovascular disease (CVD).5 Further, the diagnostic criteria for RLS are based on the International Classification of Sleep Disorders nosology.6 Confusion regarding the role of sleep disturbance in RLS may contribute to the lack of objective data regarding the sleep of such individuals in community settings. Historically, data describing the sleep of patients with RLS comes from either self-report in population-based studies or polysomnographic (PSG) studies of clinically referred patients. In a multinational study which recruited subjects from primary care providers' offices, Hening et al2 found that 88% of the 551 subjects identified as RLS sufferers by screening questionnaire (symptoms ≥ twice per week, which when present were associated with at least moderate distress) reported sleep disturbance attributed to their RLS. On nights in which RLS was present, 68% of RLS sufferers reported taking > 30 min to fall asleep, and 60% reported waking ≥ 3 times per night. In a recent PSG study of clinically referred patients Hornyak et al7 demonstrated that sleep latency was substantially longer in those with RLS (41.6 min) than in age- and gender-matched controls (25.4 min). Additional evidence of poor sleep in RLS patients included shorter total sleep time, lower sleep efficiency, higher arousal index, more stage shifts, longer REM latency, and abnormalities in the percentage of stages 1, 2, and REM sleep. Health-related quality of life (HR-QOL) is reduced in both physical and mental domains among patients with RLS.3,8,9 In one random-digit dialing study of 158 subjects with at least moderate RLS, HR-QOL was 1.2 standard deviations (SD) below the norm in physical domains and was 0.6 SD below the norm in mental/emotional health domains, even after controlling for age, gender, and disease comorbidity.9 Both were greater than QoL deficits observed in type 2 diabetes.9 In an effort to understand the genesis of RLS morbidity, the same group previously demonstrated that sleep disturbance, rather than the primary symptoms of RLS (urge to move, etc.) mediated the effects of RLS symptoms on the primary outcomes, emotional distress, and daytime alertness.3 Population-based studies may provide estimates of RLS morbidity in samples that include individuals with a wider spectrum of disease than are available in clinically referred samples, however no study to date has examined PSG-derived sleep data in a community-based sample with RLS. Similarly, no study has examined the relationship between RLS severity, as measured by PSG data, and QoL. We report the associations of PSG-derived sleep data in community dwelling individuals in relation to varying frequency and severity of RLS.