Restless legs syndrome, sleep impairment, and fatigue in chronic obstructive pulmonary disease

ObjectiveTo investigate the frequency of factors associated with restless legs syndrome (RLS) in patients with chronic obstructive pulmonary disease (COPD).MethodsRLS diagnosis was investigated (International RLS Study Group, IRLSSG) and severity was assessed (IRLS rating scale) in 104 consecutive COPD patients (age 69.1 ± 8). Other measures were dyspnea severity (Modified Medical Research Council, MMRC), sleep quality (Pittsburgh Sleep Quality Index, PSQI), daytime somnolence (Epworth Sleepiness Scale, ESS), depressive symptoms (Beck Depression Inventory, BDI-II), and fatigue (Fatigue Severity Scale, FSS). Laboratory values included hemoglobin, ferritin, creatinine, and fibrinogen.ResultsThirty-two patients (30.8%) were diagnosed with RLS (65.6% women), which was moderate/severe (IRLS >11) in 26 (81.3%). RLS symptoms started after age 40 in most patients (93.3%). RLS patients had poorer sleep quality (PSQI >5 = 59.6%; p = 0.002), worse fatigue (FSS >27 = 51%; p = 0.005), and more depressive symptoms (BDI-II >10 = 14.4%; p = 0.005). Patients with RLS also presented more severe dyspnea (p = 0.009) and lower creatinine levels (p = 0.005). Overall, fatigue severity was correlated with older age (p = 0.001); level of dyspnea was positively correlated with PSQI and FSS (p < 0.005) and negatively correlated with ferritin (p = 0.03) and creatinine (p = 0.005), and PSQI scores correlated positively with FSS (p < 0.005) and negatively with ferritin (p = 0.005) and creatinine (p = 0.02). Quality of sleep was independently predicted by dyspnea severity and creatinine and fatigue by age and depression.ConclusionRLS is common in COPD. Patients with RLS have low creatinine, poorer quality of sleep, and more fatigue and depressive symptoms. RLS symptom severity is correlated to lower ferritin and severity of dyspnea.