Table 1.
Characteristics of the study population based on BLL quartiles.
| Blood lead (μg/dL) | ||||||
|---|---|---|---|---|---|---|
| total | Q1 (0.18-0.59) | Q2 (0.59-0.82) | Q3 (0.82-1.20) | Q4 (>1.20) | P value | |
| Number of subjects (n) | 5583 | 1386 | 1386 | 1391 | 1420 | |
| Age (years) | 13.49 ± 3.35 | 14.09 ± 3.06 | 13.65 ± 3.36 | 13.28 ± 3.45 | 12.70 ± 3.43 | <0.001 |
| Gender (%) | <0.001 | |||||
| Men | 53.27% | 36.74% | 53.72% | 60.84% | 66.86% | |
| Women | 46.73% | 63.26% | 46.28% | 39.16% | 33.14% | |
| Race/ethnicity (%) | <0.001 | |||||
| Mexican American | 13.77% | 14.41% | 11.98% | 12.77% | 16.39% | |
| Other Hispanic | 5.85% | 5.11% | 5.36% | 6.20% | 7.11% | |
| Non-Hispanic White | 59.28% | 67.64% | 62.35% | 56.40% | 47.00% | |
| Non-Hispanic Black | 13.94% | 8.39% | 12.89% | 15.81% | 20.87% | |
| Other Race (Including Multi-Racial) | 7.16% | 4.45% | 7.42% | 8.83% | 8.63% | |
| PIR | 2.61 ± 1.60 | 3.00 ± 1.60 | 2.82 ± 1.55 | 2.41 ± 1.58 | 2.01 ± 1.49 | <0.001 |
| Blood urea nitrogen (mmol/L) | 3.67 ± 0.96 | 3.62 ± 0.90 | 3.64 ± 0.93 | 3.73 ± 1.09 | 3.71 ± 0.93 | 0.007 |
| Serum total calcium (mmol/L) | 2.41 ± 0.06 | 2.41 ± 0.07 | 2.41 ± 0.06 | 2.42 ± 0.07 | 2.42 ± 0.06 | <0.001 |
| Serum phosphorus (mmol/L) | 1.42 ± 0.18 | 1.40 ± 0.17 | 1.42 ± 0.18 | 1.44 ± 0.19 | 1.44 ± 0.18 | <0.001 |
| Cholesterol (mmol/L) | 4.24 ± 0.64 | 4.21 ± 0.69 | 4.24 ± 0.64 | 4.24 ± 0.61 | 4.27 ± 0.60 | 0.188 |
| Total protein (g/L) | 7.20 ± 0.33 | 7.19 ± 0.34 | 7.20 ± 0.35 | 7.19 ± 0.33 | 7.21 ± 0.30 | 0.508 |
| Serum uric acid (mmol/L) | 301.80 ± 58.97 | 291.10 ± 60.81 | 303.55 ± 59.76 | 304.96 ± 55.87 | 310.74 ± 56.69 | <0.001 |
| BMI (kg/m2) | 22.49 ± 5.68 | 23.61 ± 5.91 | 22.95 ± 5.81 | 22.15 ± 5.53 | 21.27 ± 5.19 | <0.001 |
| Total femur BMD (g/cm2) | 0.90 ± 0.19 | 0.92 ± 0.18 | 0.92 ± 0.19 | 0.89 ± 0.19 | 0.87 ± 0.19 | <0.001 |
| Femur neck (g/cm2) |
0.84 ± 0.17 | 0.86 ± 0.16 | 0.85 ± 0.18 | 0.82 ± 0.17 | 0.81 ± 0.17 | <0.001 |
| Total spine BMD (g/cm2) | 0.85 ± 0.20 | 0.90 ± 0.19 | 0.86 ± 0.20 | 0.83 ± 0.20 | 0.79 ± 0.20 | <0.001 |
| Blood lead (μg/dL) | 1.04 ± 0.87 | – | – | – | – | – |
Mean ± SD for continuous variables: the P value was calculated by the weighted linear regression model. (%) for categorical variables. The P value was calculated by the weighted chi-square test. BLL Blood lead levels. BMD bone mineral density. PIR poverty income ratio. BMI body mass index.