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Table 1 Characteristics of the study sample according to gender and educational attainment

From: Limited educational attainment and radiographic and symptomatic knee osteoarthritis: a cross-sectional analysis using data from the Johnston County (North Carolina) Osteoarthritis Project

  Men
(n = 1,053)
  Women
(n = 1,574)
  Postmenopausal Women
(n = 1,330)
 
  Educational attainment
  Low High P value Low High P value Low High P value
  (n = 402) (n = 651)   (n = 587) (n = 987)   (n = 518) (n = 812)  
Demographic characteristics          
% Age group in years    <0.001    <0.001    <0.001
45-54 19.7 42.9   17.6 44.5   12.2 35.3  
55-64 23.9 32.1   24.2 33.2   25.9 38.4  
65-74 37.8 20.7   35.8 15.8   37.8 18.6  
75+ 18.7 4.3   22.5 6.5   24.1 7.6  
% African American 36.1 19.7 <0.001 43.6 30.6 <0.001 42.9 28.7 <0.001
Lifestyle/clinical characteristics          
% Current Smokers 32.1 24.9 0.011 13.3 17.9 0.016 13.3 18.4 0.016
% Current alcohol use 20.4 34.1 <0.001 6.6 17.9 <0.001 6.2 17.2 <0.001
Mean BMI kg/m2 (SD) 27.6(5.0) 28.5(4.8) 0.004 30.2(6.7) 29.1(6.4) 0.001 30.0(6.5) 29.0(6.3) 0.005
% Knee injury 15.9 18.4 0.297 15.7 15.6 0.970 16.4 16.3 0.941
Occupation characteristics          
% Physically demanding occupationa 83.3 43.0 <0.001 82.8 38.0 <0.001 82.2 37.4 <0.001
Mean occupational physical activities score (SD)b 10.7(2.6) 10.0(2.7) <0.001 8.7(3.1) 8.8(3.0) 0.505 8.6(3.0) 8.7(3.1) 0.630
HRT use characteristics          
% Current
HRT use
N/A N/A N/A N/A N/A N/A 13.9 30.8 <0.001
Radiographic OA          
% Radiographic knee OA 32.8 22.9 <0.001 41.9 23.9 <0.001 41.9 24.9 <0.001
% Bilateral radiographic knee OA 19.9 12.1 0.001 28.7 12.7 <0.001 29.2 13.7 <0.001
Symptomatic OA          
% Symptomatic knee OA 20.2 11.1 <0.001 27.0 12.1 <0.001 27.1 13.5 <0.001
% Symptomatic bilateral knee OA 5.9 4.0 0.189 13.4 4.7 <0.001 13.1 5.0 <0.001
  1. P values are listed for comparisons between <12 years and 12+ years education within each gender category (men, women, postmenopausal women).
  2. Low educational attainment, <12 years; high educational attainment, ≥ 12 years.
  3. BMI, body mass index; HRT, hormone replacement therapy.
  4. aLaborers, fabricators, service, production, forestry, farming (as opposed to managerial, professional, technical, sales, administrative).
  5. bScale (0-16) increasing for frequency of lifting, standing, walking, and squatting.