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Table 1 Baseline population characteristics of participants eligible for data analyses

From: Health-related quality of life in relation to symptomatic and radiographic definitions of knee osteoarthritis: data from Osteoarthritis Initiative (OAI) 4-year follow-up study

Variable N (%) Mean (SD)
Participants 4278 (100.0)  
Age, years   61.1 (9.2)
 45–54 1264 (29.5)  
 55–64 1393 (32.6)  
 > 65 1621 (37.9)  
Gender
 Male 1782 (41.7)  
 Female 2496 (58.3)  
Race
 White or Caucasian 3458 (80.8)  
 Other 820 (19.2)  
Educationa
 Tertiary 1336 (31.2)  
 Secondary 1277 (29.9)  
 None / Primary 1665 (38.9)  
Living status (number of persons)   1.3 (1.1)
 Live alone 928 (21.7)  
 Living with someone else 3350 (78.3)  
BMI, kg/m2   28.5 (4.8)
 < 25 1040 (24.3)  
 25 to < 30 1690 (39.5)  
 30 to < 35 1122 (26.2)  
 ≥35 426 (10.0)  
Comorbidities   0.4 (0.8)
 score 0 3254 (76.1)  
 score > 0 1024 (23.9)  
Physical activity, PASEb   162.1 (81.8)
 238–580 798 (18.7)  
 176–237 853 (19.9)  
 135–175 866 (20.2)  
 91–134 871 (20.4)  
 0–90 890 (20.8)  
Smoking status
 Never 1977 (46.2)  
 Former 1908 (44.6)  
 Current 393 (9.2)  
Knee injuries
 No 2424 (56.7)  
 Yes 1854 (43.3)  
Knee surgical history
 No 3341 (78.1)  
 Yes 937 (21.9)  
Disutility (SF-6D) score   −0.199 (0.120)
  1. Abbreviations: BMI body mass index; Comorbidites Charlson comorbidity index score, PASE physical activity scale for the elderly, SD standard deviation
  2. aThe highest grade of school completed: tertiary (graduate degree), secondary (college graduate or some graduate school), and primary/none level (less than college)
  3. bPhysical activity PASE score quintiles (higher scores indicate greater physical activity)