Table 1.
Characteristics according to 24-h urinary sodium-to-potassium ratio in the Normative Aging Study (n = 318).
| Characteristics | Total Population (n = 318) | Tertiles of 24-h Urinary Na/K Ratio | |||
|---|---|---|---|---|---|
| Low: <2.2 (n = 106) | Medium: 2.2–3.0 (n = 106) | High: >3.0 (n = 106) | |||
| Mean ± SD | Mean ± SD | Mean ± SD | Mean ± SD | p-value 1 | |
| Age, years | 66.6 ± 7.0 | 66.9 ± 7.3 | 67.1 ± 6.7 | 65.8 ± 7.0 | 0.33 |
| BMI, kg/m2 | 27.7 ± 3.9 | 26.6 ± 3.5 | 28.2 ± 4.2 | 28.2 ± 3.8 | 0.003 |
| Urinary lead 2 (μg/day) | 4.9 (1.8) | 4.6 (1.8) | 5.0 (2.0) | 4.9 (1.7) | 0.60 |
| Patella lead 2 (μg/g) | 30.6 (1.8) | 27.8 (1.8) | 33.9 (1.7) | 30.4 (1.8) | 0.04 |
| Tibia lead 2 (μg/g) | 19.8 (1.9) | 18.6 (1.8) | 21.7 (1.8) | 19.4 (2.0) | 0.18 |
| Blood lead 2 (μg/dL) | 5.5 (2.0) | 5.0 (2.1) | 5.7 (1.9) | 6.0 (1.8) | 0.10 |
| Urinary sodium (mmol/day) | 133 ± 61.2 | 99.5 ± 40.3 | 143 ± 56.6 | 158 ± 68.0 | <0.0001 |
| Urinary potassium (mmol/day) | 53.0 ± 23.1 | 61.3 ± 24.5 | 55.7 ± 22.1 | 42.2 ± 17.9 | <0.0001 |
| Urinary Na/K ratio | 2.7 ± 1.1 | 1.7 ± 0.4 | 2.6 ± 0.2 | 3.8 ± 0.8 | <0.0001 |
| Serum creatinine (mg/dL) | 1.2 ± 0.2 | 1.2 ± 0.2 | 1.2 ± 0.1 | 1.2 ± 0.2 | 0.10 |
| Urinary creatinine (mg/dL) | 84.9 ± 44.2 | 76.8 ± 41.8 | 84.6 ± 42.4 | 93.3 ± 47.1 | 0.03 |
| Creatinine clearance rate (mL/min) | 71.1 ± 32.5 | 68.5 ± 33.9 | 70.1 ± 29.7 | 74.6 ± 33.8 | 0.37 |
| Urinary N-telopeptide (nM BCE/mM creatinine) | 54.9 ± 47.4 | 55.9 ± 38.8 | 56.9 ± 65.4 | 51.9 ± 30.8 | 0.73 |
| Dietary calcium intake (mg/day) | 826 ± 451 | 961 ± 482 | 770 ± 488 | 747 ± 342 | 0.0007 |
| Dietary vitamin C intake (mg/day) | 166 ± 101 | 195 ± 127 | 157 ± 95 | 144 ± 65 | 0.0007 |
| Total energy intake (kCal/day) | 2027 ± 896 | 2147 ± 840 | 1932 ± 1055 | 2003 ± 762 | 0.21 |
| Smoking status 3 | <0.0001 | ||||
| Never smoker | 93 (29.2%) | 32 (30.2%) | 31 (29.3%) | 30 (28.3%) | |
| Former smoker | 194 (61.0%) | 66 (62.3%) | 63 (59.4%) | 65 (61.3%) | |
| Current smoker | 31 (9.8%) | 8 (7.6%) | 12 (11.3%) | 11 (10.4%) | |
1p-values from ANOVA for all continuous variables (urinary lead, patella lead, tibia lead, and blood lead were log-transformed). p-value from the Fisher-exact test for smoking status. 2 Geometric mean (geometric standard deviation) were calculated for urinary lead, patella lead, tibia lead, and blood lead concentrations. 3 N (%) was shown for smoking status.