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Table 3 Basic characteristics of the study population in XO Study I (n = 1316)

From: Dose-response relationship between lower serum magnesium level and higher prevalence of knee chondrocalcinosis

  Tertiles of serum Mg (mmol/L)
1 (≤0.89) 2 (0.90-0.95) 3 (≥0.96)
Number 490 400 426
Median Mg level (mmol/L) 0.85 0.92 1.00
Sex (female, %) 48.6 50.3 55.2
Age (years) 63.6 ± 8.9 63.3 ± 8.4 61.6 ± 8.5
 50–59 (%) 37.1 36.3 46.4
 60–69 (%) 36.3 40.0 34.9
 ≥70 (%) 26.7 23.8 18.7
BMI (kg/m2) 24.1 ± 3.5 24.3 ± 3.9 24.3 ± 3.4
  < 25 (%) 67.6 61.0 59.9
 ≥25 (%) 32.4 39.0 40.1
Knee injury (yes, %) 5.5 3.8 5.2
Serum PTH (μmol/L) 52.5 ± 38.0 54.8 ± 23.1 51.3 ± 20.2
Serum iron (μmol/L) 20.2 ± 8.6 19.8 ± 7.2 20.3 ± 7.8
Serum TIBC (μmol/L) 58.3 ± 11.3 59.1 ± 11.6 60.2 ± 11.4
Serum UIBC (μmol/L) 38.2 ± 13.5 39.5 ± 13.2 40.0 ± 13.1
Serum calcium (mmol/L) 2.3 ± 0.1 2.3 ± 0.1 2.3 ± 0.1
Serum 25(OH)D (μg/L) 25.8 ± 11.3 24.9 ± 9.9 25.9 ± 10.9
Serum zinc (μmol/L) 17.3 ± 3.5 18.5 ± 3.7 19.9 ± 6.1
Serum copper (μmol/L) 16.3 ± 3.2 16.4 ± 3.7 16.8 ± 3.5
Serum phosphorus (mmol/L) 1.2 ± 0.2 1.2 ± 0.2 1.2 ± 0.2
Education (educated, %) 70.2 66.5 67.8
Occupation (farmer, %) 85.5 87.3 85.7
  1. Mg magnesium, BMI body mass index, PTH parathyroid hormone, TIBC, total iron binding capacity, UIBC unsaturated iron-binding capacity