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Table 1 Characteristics of the study population by serum copper quartile

From: The association between serum copper concentrations and elevated blood pressure in US children and adolescents: National Health and Nutrition Examination Survey 2011–2016

  Total
(n = 1242)
1st
(n = 312)
2nd
(n = 309)
3rd
(n = 312)
4th
(n = 309)
P value
Male 624 (50.2) 168 (53.8) 135 (43.7) 138 (44.2) 183 (59.2) < 0.001
Race/ethnicity       < 0.001
 Mexican American 261 (21.0) 60 (19.2) 81 (26.2) 66 (21.2) 54 (17.5)  
 Other Hispanic 120 (9.7) 30 (9.6) 33 (10.7) 39 (12.5) 18 (5.8)  
Non-Hispanic White 300 (24.2) 78 (25.0) 87 (28.2) 72 (23.1) 63 (20.4)  
 Non-Hispanic Black 357 (28.7) 75 (24.0) 63 (20.4) 81 (26.0) 138 (44.7)  
 Other Race 204 (16.4) 69 (22.1) 45 (14.6) 54 (17.3) 36 (11.7)  
Family monthly poverty level category       0.001
 < 1.30 579 (46.6) 144 (46.2) 123 (39.8) 138 (44.2) 174 (56.3)  
 1.31–1.85 174 (14.0) 57 (18.3) 51 (16.5) 39 (12.5) 27 (8.7)  
 > 1.85 438 (35.3) 105 (33.7) 126 (40.8) 117 (37.5) 90 (29.1)  
Age (years) 12.2 (2.9) 13.5 (2.5) 12.2 (2.9) 11.7 (3.0) 11.3 (2.9) < 0.001
BMI       < 0.001
 Underweight 39 (3.1) 12 (3.8) 15 (4.9) 3 (1.0) 9 (2.9)  
 Normal 714 (57.5) 231 (74.0) 183 (59.2) 174 (55.8) 126 (40.8)  
 Overweight 225 (12.5) 39 (21.4) 66 (22.1) 69 (16.5) 51 (18.1)  
 Obese 264 (21.3) 30 (9.6) 45 (14.6) 66 (21.2) 123 (39.8)  
Height, cm 152.1 (15.6) 153.1 (13.6) 152.4 (14.8) 150.9 (14.2) 152.0 (15.6) 0.243
Energy intake (kcal/day) 1920 (635) 2000 (681) 1900 (661) 1870 (559) 1890 (630) 0.063
Physical activity       0.154
 Low 558 (44.9) 132 (42.3) 135 (43.7) 135 (43.3) 156 (50.5)  
 High 684 (55.1) 180 (57.7) 174 (56.3) 177 (56.7) 153 (49.5)  
SBP, mm Hg 105.1 (9.4) 103.2 (8.7) 104.0 (8.7) 105.1 (10.0) 108.0 (9.6) < 0.001
DBP, mm Hg 62.6 (6.1) 59.3 (4.8) 61.8 (6.4) 63.8 (6.6) 65.6 (4.6) < 0.001
Serum copper, μg/dL 114.2 (26.5) 86.7 (7.7) 103.2 (4.2) 118.3 (5.2) 148.7 (25.0) < 0.001
Serum cotinine (ng/mL) 3.8 (30.1) 10.3 (56.0) 3.0 (19.2) 0.9 (6.9) 0.9 (2.3) 0.006
Urinary manganese (μg/L) 0.2 (0.19) 0.19 (0.16) 0.17 (0.12) 0.19 (0.28) 0.19 (0.19) 0.347
Urinary lead (μg/L) 0.47 (0.5) 0.42 (0.3) 0.40 (0.3) 0.44 (0.4) 0.60 (0.8) 0.001
Urinary strontium (μg/L) 131 (123) 144 (117) 119 (100) 142 (167) 118 (89) 0.003
Urinary mercury (μg/L) 0.49 (0.71) 0.50 (0.74) 0.49 (0.72) 0.44 (0.70) 0.54 (0.67) 0.339
Urinary arsenic (μg/L) 11.3 (26.4) 13.5 (44.5) 9.8 (12.8) 12.0 (16.7) 10.1 (18.9) 0.273
Serum selenium (μg/L) 121 (16.6) 122 (13.3) 120 (13.8) 121 (13.7) 120 (23.4) 0.202
Serum zinc (μg/dL) 83.7 (16.3) 80.9 (12.7) 82.2 (14.1) 84.4 (13.4) 87.4 (22.5) < 0.001
  1. BMI, body mass index; SBP, systolic blood pressure; DBP, diastolic blood pressure