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Table 1 Characteristics of study population and between-group comparison; USRDS 2006–2008

From: Association of restless legs syndrome and mortality in end-stage renal disease: an analysis of the United States Renal Data System (USRDS)

Variable Total n = 279,956 RLS n = 372 NSD n = 279,584 P
Incidence age, years 62.05 ± 15.39 64.22 ± 15.64 62.04 ± 15.39 0.007
Gender     0.2
 Female 43.72 (122,400) 47.3 (176) 43.7 (122,224)  
 Male 56.28 (157,556) 52.7 (196) 56.3 (157,360)  
Race     <.0001
 White 64.38 (180,239) 86.29 (321) 64.35 (179,918)  
 Black 29.93 (83,782) 11.56 (43) 29.95 (83,739)  
 Asian 3.32 (9282) 1.34 (5) 3.32 (9277)  
 Native American 1.08 (3026) 0.27 (1) 1.08 (3025)  
 Other/Unknown 1.3 (3627) 0.54 (2) 1.3 (3625)  
Ethnicity     0.002
 Non-Hispanic/Latino 85.68 (239,880) 91.4 (340) 85.68 (239,540)  
 Hispanic/Latino 14.32 (40,076) 8.6 (32) 14.32 (40,044)  
Vascular access type     0.0002
 AV Fistula 14.61 (40,902) 23.12 (86) 14.6 (40,816)  
 Graft 3.95 (11,058) 4.3 (16) 3.95 (11,042)  
 Catheter 80.28 (224,739) 71.77 (267) 80.29 (224,472)  
 Other/Unknown 1.16 (3257) 0.81 (3) 1.16 (3254)  
Body mass index (kg/m2)f 28.74 ± 7.71 28.98 ± 7.57 28.74 ± 7.71 0.5
Serum creatinine (mg/dl)f 6.58 ± 3.46 6.64 ± 3.74 6.58 ± 3.46 0.8
Serum albumin (g/dl)f 3.11 ± 0.71 3.32 ± 0.64 3.11 ± 0.71 <.0001
Anemiaa 8.37 (23,432) 11.83 (44) 8.37 (23,388) 0.02
Cardiovascular
 Coronary artery diseaseb 21.09 (59,054) 17.2 (64) 21.1 (58,990) 0.07
 Congestive heart failure 32.18 (90,088) 26.34 (98) 32.19 (89,990) 0.02
 Cerebrovascular disease 9.4 (26,329) 8.06 (30) 9.41 (26,299) 0.4
 Peripheral vascular disease 14.04 (39,301) 10.22 (38) 14.04 (39,263) 0.03
 Hypertension 84.92 (237,737) 83.6 (311) 84.92 (237,426) 0.5
Other
 Diabetes 52.78 (147,771) 38.98 (145) 52.8 (147,626) <.0001
 Cancer 6.81 (19,065) 5.91 (22) 6.81 (19,043) 0.5
Sleep disorders
 Any sleep disorder 0.13 (372) 100.0 (372) 0 (0) <.0001
 Restless legs syndrome 0.13 (372) 100.0 (372) 0 (0) <.0001
 Obstructive sleep apnea 0.01 (17) 4.57 (17) 0 (0) <.0001
Psychological disorders
 Major depressive disorder 0.37 (1030) 1.61 (6) 0.37 (1024) <.0001
 Dysthymic disorder 0.26 (727) 2.15 (8) 0.26 (719) <.0001
 Anxiety 0.6 (1691) 4.03 (15) 0.6 (1676) <.0001
 Adjustment disorder 0.03 (81) 0.27 (1) 0.03 (80) 0.1
 Depressionc 0.65 (1829) 4.03 (15) 0.65 (1814) <.0001
 Minor depressive disorderd 0.29 (808) 2.42 (9) 0.29 (799) <.0001
 Psychological disordere 1.24 (3459) 8.06 (30) 1.23 (3429) <.0001
Tobacco dependence 6.39 (17,887) 8.87 (33) 6.39 (17,854) 0.05
Alcohol dependence 1.57 (4384) 0.81 (3) 1.57 (4381) 0.2
Drug dependence 1.55 (4339) 1.08 (4) 1.55 (4335) 0.5
  1. Age and clinical measures are mean ± SD. Categorical data are percentages (counts). No sleep disorder diagnosed (NSD)
  2. aDetermined by ICD-9-CM codes 280.0–280.9, 285.0, 285.2, 285.8, 285.9
  3. bAtherosclerosis, myocardial infarction (MI), ischemic heart disease (IHD)
  4. cmajor depressive disorder, dysthymic disorder, adjustment disorder
  5. dDysthymic disorder, adjustment disorder
  6. eDepression, anxiety
  7. fMissing data points