Table 1.
Baseline characteristics of the study population according to urine SGU quartile status
| Characteristic | Quartile of urine SGU | P-trend | |||
|---|---|---|---|---|---|
|
| |||||
| < 1.4 (n = 5,261) | 1.4 to 1.8 (n = 6,355) | 1.8 to 2.2 (n = 6,988) | ≥2.2 (n = 9,738) | ||
| Age (yr) | 53.8 ± 15.5 | 55.1 ± 15.5a | 52.1 ± 15.4a,b | 44.9 ± 15.4a,b,c | < 0.001 |
| Sex, male (%) | 29.9 | 40.4a | 48.1a,b | 54.6a,b,c | < 0.001 |
| Current smoker (%) | 15.2 | 17.1a | 22.3a,b | 26.9a,b,c | < 0.001 |
| Frequent drinker (%) | 16.0 | 19.5a | 25.2a,b | 24.9a,b | < 0.001 |
| Regular walking (%) | 27.0 | 26.6 | 26.5 | 27.0 | 0.820 |
| Hypertension (%) | 38.0 | 40.6a | 34.4a,b | 26.1a,b,c | < 0.001 |
| Diabetes (%) | 12.6 | 13.3 | 10.3a,b | 9.9a,b | < 0.001 |
| Dyslipidemia (%) | 20.8 | 21.4 | 19.1a,b | 15.8a,b,c | < 0.001 |
| Cardiovascular disease (%) | 5.0 | 5.6 | 4.7b | 2.8a,b,c | < 0.001 |
| BMI (kg/m2) | 23.5 ± 3.2 | 23.8 ± 3.3a | 23.8 ± 3.4a | 23.9 ± 3.5a | 0.008 |
| Waist circumference (cm) | 80.8 ± 9.5 | 82.0 ± 9.7a | 82.1 ± 9.8a | 81.8 ± 10.3a | 0.025 |
| Systolic BP (mmHg) | 122.3 ± 18.9 | 123.0 ± 18.6 | 120.7 ± 16.8a,b | 117.1 ± 15.5a,b,c | < 0.001 |
| Diastolic BP (mmHg) | 76.2 ± 10.7 | 76.8 ± 10.7 | 76.8 ± 10.4 | 76.3 ± 10.3 | 0.608 |
| Pulse rate (counts/min) | 69.9 ± 9.2 | 69.9 ± 9.3 | 70.1 ± 9.3 | 70.4 ± 9.8 | 0.002 |
| Fasting glucose (mmol/L) | 5.44 ± 1.11 | 5.50 ± 1.12 | 5.46 ± 1.11 | 5.54 ± 1.60a,c | < 0.001 |
| Total cholesterol (mmol/L) | 4.90 ± 0.93 | 4.91 ± 0.94 | 4.93 ± 0.93 | 4.88 ± 0.93c | 0.488 |
| eGFR (mL/min/1.73 m2) | 92.9 ± 18.2 | 91.0 ± 17.9a | 93.7 ± 16.3b | 98.4 ± 15.9a,b,c | < 0.001 |
| ≥ 90 (%) | 60.3 | 55.0a | 61.3b | 70.9a,b,c | < 0.001 |
| 60–90 (%) | 34.7 | 39.5a | 35.7b | 27.8a,b,c | < 0.001 |
| 30–60 (%) | 4.4 | 5.2a | 2.9a,b | 1.3a,b,c | < 0.001 |
| < 30 (%) | 0.6 | 0.3a | 0.1a,b | 0.0a,b,c | < 0.001 |
| BUN (mmol/L) | 4.7 ± 1.8 | 5.1 ± 1.5a | 5.2 ± 1.5a,b | 5.5 ± 1.5a,b,c | < 0.001 |
| Serum creatinine (μmol/L) | 71.2 ± 30.5 | 73.4 ± 23.3a | 73.4 ± 16.4a | 74.5 ± 15.3a,b,c | < 0.001 |
| Urine SGU | 1.0 ± 0.2 | 1.5 ± 0.1a | 1.9 ± 0.1a,b | 2.5 ± 0.3a,b,c | < 0.001 |
| Urine sodium (mmol/L) | 81.1 ± 36.3 | 123.3 ± 42.6a | 140.0 ± 48.6a,b | 137.7 ± 51.9a,b | < 0.001 |
| Urine creatinine (mmol/L) | 5.1 ± 2.1 | 9.0 ± 2.9a | 13.0 ± 4.0a,b | 19.6 ± 6.9a,b,c | < 0.001 |
| Urine sodium to creatinine | 18.7 ± 11.9 | 15.7 ± 8.7a | 12.3 ± 7.3a,b | 8.3 ± 5.1a,b,c | < 0.001 |
| High water intake (%) | 34.4 | 29.6a | 27.6a | 27.9a,b | < 0.001 |
| Proteinuria (%) | 0.7 | 1.4a | 1.1a,b | 1.4a | 0.002 |
Data are presented as mean ± standard deviation for continuous variables and a percentage for categorical variables.
Conversion factor from conversional unit to SI unit was in × 0.0555 in glucose, × 0.0259 in cholesterol, × 0.357 in BUN, and × 88.4 in serum and urine creatinine, respectively.
BMI, body mass index; BP, blood pressure; BUN, blood urea nitrogen; eGFR, estimated glomerular filtration rate; SGU, specific gravity unit.
P value was analyzed by the linear-term of a one-way ANOVA for continuous variables and a linear-by-linear association for categorical variables.
are defined as P = 0.008 when compared to the < 1.4, 1.4 to 1.8, and 1.8 to 2.2 groups, respectively, with a Bonferroni post-hoc analysis of one-way ANOVA for continuous variables and a chi-squared test for categorical variables.