Table 1.
Participant Characteristics by Quartiles of Serum Bicarbonate Levels by Sex
| Men | Women | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Characteristic | < 24 | 24-25 | 25.1-26.9 | ≥ 27 | P | < 24 | 24-25 | 25.1-26.9 | ≥ 27 | P |
| No. of participants | 1120 | 1175 | 1500 | 1298 | 1453 | 1180 | 1211 | 787 | ||
| Age (y) | 44 (0.5) | 45 (0.5) | 44 (0.4) | 45 (0.6) | 0.06 | 41 (0.5) | 45 (0.6) | 48 (0.6) | 54 (0.8) | <0.001 |
| Race/Ethnicity | 0.07 | 0.02 | ||||||||
| Non-Hispanic White | 72% (2.6%) | 73% (2.6%) | 71% (2.3%) | 72% (1.9%) | 70% (2.2%) | 71% (2.5%) | 72% (2.3%) | 73% (2.1%) | ||
| Mexican American | 10.4% (1.8%) | 9.2% (1.2%) | 8.7% (1.0%) | 5.5% (0.7%) | 9.2% (1.6%) | 6.9% (1.0%) | 5.9% (0.7%) | 3.4% (0.5%) | ||
| Non-Hispanic Black | 8.0% (1.2%) | 8.0% (1.1%) | 10.1% (1.0%) | 11.3% (1.1%) | 10.2% (1.5%) | 11.2% (1.3%) | 12.2% (1.4%) | 12.6% (1.6%) | ||
| Body-mass index (kg/m2) | 29.4 (0.2) | 28.2 (0.2) | 27.8 (0.2) | 26.7 (0.2) | <0.001 | 29.1 (0.3) | 27.6 (0.3) | 27.8 (0.2) | 27.0 (0.3) | <0.001 |
| Poverty* | 11.7% (1.0%) | 10.5% (1.0%) | 11.0% (0.8%) | 9.0% (1.1%) | 0.1 | 17.5% (1.2%) | 14.5% (1.5%) | 13.8% (1.2%) | 11.1% (1.2%) | <0.001 |
| <High school diploma | 21.4% (1.7%) | 18.7% (1.2%) | 19.5% (1.4%) | 17.1% (1.3%) | 0.05 | 18.9% (1.1%) | 17.1% (1.2%) | 19.2% (1.4%) | 19.4% (1.6%) | 0.6 |
| Activity Level | 0.5 | 0.09 | ||||||||
| 0 MET-min/wk | 12.9% (1.4%) | 12.4% (1.0%) | 13.8% (1.3%) | 12.0% (1.2%) | 18.1% (1.1%) | 15.6% (1.2%) | 18.8% (1.5%) | 18.9% (1.5%) | ||
| <500 MET-min/wk | 21.2% (1.7%) | 20.0% (1.7%) | 17.9% (1.1%) | 18.2% (1.3%) | 22.7% (1.5%) | 21.9% (1.2%) | 19.1% (1.5%) | 24.4% (1.6%) | ||
| 500-2000 MET-min/wk | 36.1% (2.0%) | 34.2% (1.2%) | 36.9% (1.5%) | 35.3% (1.5%) | 34.4% (1.6%) | 35.2% (1.6%) | 38.7% (1.7%) | 32.5% (1.9%) | ||
| >2000 MET-min/wk | 29.8% (2.0%) | 33.4% (1.8%) | 31.5% (2.1%) | 34.5% (1.5%) | 24.9% (1.3%) | 27.3% (1.8%) | 23.4% (1.4%) | 24.2% (2.2%) | ||
| Smoking | <0.001 | <0.001 | ||||||||
| Never | 40.3% (2.6%) | 39.7% (2.0%) | 44.6% (1.7%) | 48.9% (1.9%) | 54.8% (2.5%) | 58.8% (1.6%) | 62.5% (1.6%) | 61.6% (1.6%) | ||
| Former | 26.8% (1.4%) | 28.5% (1.5%) | 28.7% (1.6%) | 29.6% (1.4%) | 18.7% (1.7%) | 20.7% (1.4%) | 20.0% (1.3%) | 23.3% (2.0%) | ||
| Current | 32.8% (2.5%) | 31.8% (1.5%) | 26.6% (1.4%) | 21.6% (1.6%) | 26.6% (1.6%) | 20.6% (1.6%) | 17.5% (1.1%) | 15.1% (1.6%) | ||
| Estimated NEAP (mEq/d) | 63.1 (0.9) | 62.8 (1.0) | 59.7 (0.9) | 57.1 (0.7) | <0.001 | 59.3 (0.8) | 57.6 (1.0) | 51.5 (0.7) | 48.5 (1.1) | <0.001 |
| Fasting length ≤2 h | 2.9 (0.5) | 2.4 (0.5) | 3.3 (0.5) | 2.9 (0.6) | 0.6 | 2.2 (0.5) | 2.3 (0.5) | 3.1 (0.5) | 4.3 (0.9) | 0.02 |
| Diuretic use | 7.1% (0.8%) | 6.2% (0.8%) | 6.4% (0.8%) | 10.6% (1.2%) | 0.02 | 5.5% (0.7%) | 9.3% (1.2%) | 13.2% (1.3%) | 25.3% (1.9%) | <0.001 |
| Calcium carbonate use | 5.1% (0.9%) | 3.2% (0.7%) | 5.4% (0.7%) | 4.3% (1.1%) | 0.9 | 2.4% (0.5%) | 3.3% (0.8%) | 4.3% (0.7%) | 5.3% (1.3%) | 0.02 |
| Hypertension | 43.1% (1.8%) | 36.5% (1.7%) | 35.3% (1.7%) | 36.5% (1.9%) | 0.01 | 33.3% (1.3%) | 35.7% (1.6%) | 41.4% (2.0%) | 53.5% (2.1%) | <0.001 |
| Diabetes Mellitus | 11.2% (1.1%) | 8.9% (1.1%) | 7.8% (0.8%) | 6.4% (0.7%) | <0.001 | 7.6% (0.7%) | 5.7% (0.6%) | 7.9% (0.7%) | 11.5% (1.2%) | 0.01 |
| Cardiovascular disease | 9.8% (1.0%) | 8.0% (1.1%) | 8.6% (0.9%) | 6.8% (0.7%) | 0.03 | 5.2% (0.5%) | 6.0% (0.8%) | 6.9% (0.9%) | 8.5% (0.9%) | 0.001 |
| eGFR (mL/min/1.73 m2) | 94.1 (0.8) | 93.9 (0.7) | 94.3 (0.7) | 92.8 (0.6) | 0.2 | 98.8 (0.7) | 95.9 (0.8) | 93.6 (0.8) | 88.6 (1.1) | <0.001 |
| Urine ACR > 30 mg/g | 10.4% (0.8%) | 8.6% (0.8%) | 6.9% (0.7%) | 6.7% (0.8%) | 0.001 | 9.0% (0.7%) | 8.9% (0.9%) | 9.0% (1.0%) | 10.1% (1.1%) | 0.6 |
| Serum albumin (g/dL) | 4.41 (0.01) | 4.43 (0.02) | 4.45 (0.01) | 4.50 (0.02) | <0.001 | 4.24 (0.01) | 4.25 (0.01) | 4.27 (0.01) | 4.26 (0.02) | 0.2 |
| Serum calcium (mg/dL) | 9.48 (0.02) | 9.56 (0.02) | 9.53 (0.02) | 9.56 (0.02) | 0.06 | 9.39 (0.02) | 9.47 (0.02) | 9.44 (0.02) | 9.52 (0.03) | <0.001 |
| Serum phosphate (mg/dL) | 3.63 (0.03) | 3.67 (0.02) | 3.57 (0.02) | 3.59 (0.02) | 0.08 | 3.68 (0.02) | 3.76 (0.02) | 3.69 (0.02) | 3.78 (0.02) | 0.03 |
| C-reactive protein ≥1.0 mg/dL | 6.3% (1.0%) | 5.1% (0.7%) | 5.4% (0.6%) | 4.8% (0.6%) | 0.2 | 14.8% (1.2%) 8 | 10.4% (1.0%) | 11.7% (1.5%) | 12.4% (1.5%) | 0.2 |
| Lumbar BMD (g/cm2) | 1.05 (0.006) | 1.04 (0.007) | 1.05 (0.005) | 1.06 (0.006) | 0.1 | 1.05 (0.004) | 1.05 (0.006) | 1.05 (0.004) | 1.03 (0.007) | 0.03 |
| Total BMD (g/cm2) | 1.19 (0.005) | 1.19 (0.005) | 1.19 (0.004) | 1.19 (0.004) | 0.9 | 1.10 (0.003) | 1.10 (0.004) | 1.09 (0.003) | 1.08 (0.006) | <0.001 |
Note: Unless otherwise indicated, values for categorical variables are given as percentage (standard error); values for continuous variables, as mean ± standard error. Serum bicarbonate is expressed as mEq/L. Conversion factor for serum calcium in mg/dL to mmol/L, ×0.2495.
Abbreviations: MET, metabolic equivalent; NEAP, net endogenous acid production; eGFR, estimated glomerular filtration rate; ACR, albumin-creatinine ratio; BMD, bone mineral density.