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Table 1 Participant characteristics

From: Associations between serum calcium, 25(OH)D level and bone mineral density in adolescents

Characteristic Boys (n = 3086) Girls (n = 2904) P value
Age, mean ± SD (years) 15.46 ± 2.26 15.35 ± 2.23 0.0551
Race/Ethnicity (%)    0.9754
 Non-Hispanic White 62.87 63.15  
 Non-Hispanic Black 14.47 14.48  
 Mexican American 11.50 11.13  
 Other race/ethnicity 11.16 11.25  
BMI, mean ± SD (kg/m2) 23.31 ± 5.50 23.55 ± 5.78 0.1073
Income to poverty ratio, mean ± SD 2.64 ± 1.62 2.57 ± 1.62 0.0912
Physical activity (%)    < 0.0001
 Sedentary 2.95 4.85  
 Low 7.72 11.63  
 Moderate 6.51 8.47  
 High 22.05 16.20  
 Not recorded 60.77 58.85  
Calcium supplementation (%)    < 0.0001
 Not use 87.21 83.80  
  < 0.4 g/d 10.94 12.99  
  ≥ 0.4 g/d 1.84 3.21  
Serum calcium, mean ± SD (mg/dL) 9.80 ± 0.30 9.64 ± 0.30 < 0.0001
Serum vitamin D, mean ± SD (ng/mL) 24.23 ± 8.63 23.32 ± 10.02 0.0002
Total BMD, mean ± SD (g/cm2) 1.10 ± 0.14 1.06 ± 0.10 < 0.0001
  1. Mean ± SD for continuous variables: P value was calculated by weighted linear regression model
  2. % for categorical variables: P value was calculated by weighted chi-square test
  3. Abbreviation: BMI, body mass index, BMD bone mineral density