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Table 1 Baseline characteristics of subjects

From: Estimation of the cutoff value of vitamin D: the Dong-gu study

  Male Female Total P values
N (%) 3,545 (40.0) 5,312 (60.0) 8,857 (100.0) -
Age (years) 66.1 ± 8.0 64.4 ± 8.2 65.1 ± 8.1 <0.001
BMI (kg/m2) 23.9 ± 2.8 24.6 ± 3.0 24.3 ± 2.9 <0.001
Month of blood collection     0.004
  April 762 (21.5) 1,010 (19.0) 1,772 (20.0)  
  May 1,132 (31.9) 1,749 (32.9) 2,881 (32.5)  
  June 1,079 (30.4) 1,580 (29.7) 2,659 (30.0)  
  July 572 (16.1) 973 (18.3) 1,545 (17.4)  
Smoking (%) 865 (24.4) 99 (1.9) 964 (10.9) <0.001
Alcohol intake (%) 2,416 (68.2) 1,690 (31.8) 4,106 (46.4) <0.001
Physically activea (%) 920 (26.8) 667 (13.0) 1,587 (18.5) <0.001
PTH (pg/ml) 40.6 ± 17.7 44.0 ± 19.4 42.7 ± 18.8 <0.001
25(OH)D (ng/ml) 19.2 ± 5.9 15.0 ± 5.1 16.7 ± 5.8 <0.001
Vitamin D deficientb (%) 2,120 (59.8) 4,595 (86.5) 6,715 (75.8) <0.001
Postmenopause (%)   5,081 (96.2)   
  1. All values are given as N (%) or mean ± standard deviation. BMI, body mass index; 25(OH)D, 25-hydroxyvitamin D; PTH, parathyroid hormone. aSubjects who performed 30 min or more of moderate activity at least 5 days a week or 20 min of vigorous physical activity at least 3 days a week were regarded as doing physical activity; b25(OH)D <20 ng/ml.