Table 1.
Baseline characteristics of the study population according to quartiles of interleukin-6 levels
| IL-6, pg/ml | Quartile 1 N = 970 ≤ 1.2 |
Quartile 2 N = 968 > 1.2 and ≤ 1.9 |
Quartile 3 N = 969 > 1.9 and ≤ 3.2 |
Quartile 4 N = 968 > 3.2 |
|---|---|---|---|---|
| Demographics | ||||
| Age, years | 54.5 ± 11.7 | 57.7 ± 11.0 | 59.4 ± 10.3 | 59.0 ± 10.3 |
| Female, N (%) | 405 (41.8) | 448 (46.3) | 437 (45.1) | 446 (46.1) |
| Black, N (%) | 326 (33.6) | 377 (39.0) | 449 (46.3) | 467 (48.2) |
| Hispanic, N (%) | 70 (7.2) | 127 (13.1) | 143 (14.8) | 155 (16.0) |
| Cardiovascular risk factors | ||||
| Hypertension, N (%) | 729 (75.2) | 843 (87.1) | 873 (90.1) | 890 (91.9) |
| Diabetes, N (%) | 305 (31.4) | 463 (47.8) | 555 (57.3) | 556 (57.4) |
| Coronary artery disease, N (%) | 119 (12.3) | 204 (21.1) | 244 (25.2) | 285 (29.4) |
| Congestive heart failure, N (%) | 38 (3.9) | 75 (7.8) | 109 (11.3) | 154 (15.9) |
| Stroke, N (%) | 62 (6.4) | 97 (10.0) | 108 (11.2) | 118 (12.2) |
| Peripheral vascular disease, N (%) | 20 (2.1) | 66 (6.8) | 75 (7.7) | 97 (10.0) |
| Current smoking, N (%) | 94 (9.7) | 128 (13.2) | 116 (12.0) | 170 (17.6) |
| Body mass index, kg/m2 | 28.9 ± 5.7 | 31.7 ± 7.0 | 33.5 ± 7.9 | 34.3 ± 9.1 |
| Systolic blood pressure, mm Hg | 122.1 ± 18.9 | 128.9 ± 21.5 | 131.5 ± 23.5 | 131.9 ± 23.3 |
| Medication use | ||||
| Aspirin, N (%) | 363 (37.6) | 395 (41.2) | 470 (48.9) | 422 (43.8) |
| B -blockers, N (%) | 325 (33.7) | 462 (48.2) | 546 (56.8) | 564 (58.6) |
| Statins, N (%) | 459 (47.6) | 548 (57.2) | 583 (60.7) | 534 (55.5) |
| ACE inhibitors or ARBs, N (%) | 604 (62.6) | 702 (73.3) | 686 (71.4) | 656 (68.1) |
| Phosphate binders, N (%) | 65 (6.7) | 69 (7.2) | 67 (7.0) | 69 (7.2) |
| Active vitamin D, N (%) | 22 (2.3) | 22 (2.3) | 34 (3.5) | 46 (4.8) |
| Nutritional Vitamin D, N (%) | 130 (13.5) | 92 (9.6) | 84 (8.7) | 91 (9.5) |
| Steroids, N (%) | 94 (9.7) | 87 (9.1) | 83 (8.6) | 122 (12.7) |
| CKD Specific Risk Factors | ||||
| Creatinine, mg/dl | 1.6 ± 0.6 | 1.8 ± 0.6 | 1.9 ± 0.6 | 2.0 ± 0.7 |
| eGFR, ml/min/1.73m2 | 51.0 ± 15.9 | 44.4 ± 14.0 | 41.9 ± 13.5 | 39.9 ± 14.2 |
| Urinary ACR, mg/g | 17.0 (5.3 – 176.2) | 48.5 (8.0 – 427.7) | 73.1 (11.8 – 649.0) | 117.4 (17.9 – 810.5) |
| Hemoglobin, g/dl | 13.2 ± 1.7 | 12.7 ±1.7 | 12.4 ± 1.8 | 12.1 ± 1.8 |
| Albumin, g/dl | 4.1 ± 0.4 | 4.0 ± 0.5 | 3.9 ± 0.5 | 3.8 ± 0.5 |
| LDL, mg/dl | 106.3 ± 33.5 | 104.1 ±35.8 | 101.6 ± 36.7 | 98.3 ± 34.9 |
| Mineral Metabolites | ||||
| Calcium, mg/dl | 9.3 ± 0.5 | 9.2 ± 0.5 | 9.1 ± 0.5 | 9.1 ± 0.5 |
| Phosphate, mg/dl | 3.6 ± 0.6 | 3.7 ± 0.7 | 3.8 ± 0.7 | 3.8 ± 0.7 |
| Parathyroid hormone, pg/ml | 41.3 (29.0 – 63.0) | 52.9 (34.0 – 82.0) | 58.0 (38.5 –102.4) | 71.0 (43.0 – 115.6) |
| FGF23, RU/ml | 103.0 (73.6 – 150.5) | 141.3 (94.2 – 210.2) | 160.9 (109.7 – 243.5) | 217.3 (127.3 – 364.0) |
| Inflammatory markers | ||||
| IL-6, pg/ml | 0.8 (0.6 – 1.0) | 1.5 (1.3 – 1.7) | 2.4 (2.1 – 2.7) | 4.8 (3.7 – 7.2) |
| HS-CRP, mg/l | 1.2 (0.6 – 2.4) | 2.0 (1.0 – 4.1) | 3.4 (1.4 – 7.2) | 6.7 (2.8 – 13.1) |
| TNF-α, pg/ml | 1.7 (1.2 – 2.4) | 2.2 (1.5 – 3.1) | 2.4 (1.7 – 3.4) | 2.8 (2.0 – 4.0) |
| Fibrinogen, g/l | 3.4 (3.0 – 4.0) | 3.9 (3.4 – 4.5) | 4.3 (3.6 – 5.0) | 4.7 (4.0 – 5.6) |
Values expressed as mean ± SD or median (interquartile range).
ACE, angiotensin-converting enzyme; ARB, angiotensin II receptor blocker; eGFR, estimated glomerular filtration rate; ACR, albumin to creatinine ratio; LDL, low-density lipoprotein; FGF23, fibroblast growth factor 23; IL-6, interleukin-6; CRP, high sensitive C-reactive protein; TNF-α, tumor necrosis factor alpha.