Table 1.
Characteristics of the study population by serum copper quartile
| 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 |
BMI, body mass index; SBP, systolic blood pressure; DBP, diastolic blood pressure