Table 1.
Baseline Characteristic of the Study Participants with Chronic Kidney Disease (n=2142)
| Characteristics | Quintile Categories of Serum Folate, ng/mL | p-values | ||||
|---|---|---|---|---|---|---|
| Q1 (<8.7) | Q2 (8.7–11.4) | Q3 (11.5–14.6) | Q4 (14.7–19.1) | Q5 (≥19.2) | ||
| N | 422 | 431 | 428 | 427 | 434 | |
| Age (yr) | 45.42 (18.32) | 44.22 (18.03) | 48.54 (18.90) | 51.03 (19.48) | 59.73 (20.38) | <0.001 |
| BMI (Kg/m2) | 29.07 (6.59) | 28.86 (7.05) | 27.96 (5.93) | 27.40 (5.40) | 27.17 (5.45) | <0.001 |
| eGFR (mL/min/1.73 m2) | 46.87 (9.80) | 47.20 (9.73) | 44.94 (10.66) | 44.42 (10.66) | 42.51 (10.13) | <0.001 |
| Urinary albumin (ug/mL) | 9.00 (0.40–4870.00) | 8.40 (0.40–9910.00) | 8.40 (0.20–9820.00) | 7.60 (0.30–3580.00) | 8.40 (0.20–7570.00) | 0.064 |
| Urinary creatinine (g/L) | 1.28 (0.12–4.59) | 1.24 (0.09–5.34) | 1.15 (0.09–7.74) | 1.05 (0.07–5.48) | 0.86 (0.06–3.98) | <0.001 |
| Time to death or censorship from time of examination (months) | 56.12 (11.84) | 58.28 (9.40) | 57.76 (9.67) | 58.60 (8.79) | 56.24 (12.21) | <0.001 |
| Folate as dietary folate equivalents (mcg) | 410.00 (0.00–2781.00) | 423.00 (0.00–5715.00) | 454.00 (66.00–2388.00) | 477.00 (66.00–6635.00) | 494.00 (38.00–3126.00) | <0.001 |
| Food folate (mcg) | 157.50 (0.00–1557.00) | 178.00 (0.00–1209.00) | 184.00 (23.00–702.00) | 188.00 (16.00–1242.00) | 189.50 (12.00–1227.00) | <0.001 |
| Hemoglobin A1c (%) | 5.61 (1.01) | 5.65 (1.21) | 5.61 (1.11) | 5.58 (1.05) | 5.60 (1.06) | 0.895 |
| Serum Vitamin B12 (pg/mL) | 412.00 (100.00–9442.00) | 423.00 (94.00–52710.00) | 454.00 (80.00–16114.00) | 475.00 (94.00–2710.00) | 575.50 (100.00–3076.00) | <0.001 |
| Albumin (g/dL) | 4.13 (0.35) | 4.18 (0.33) | 4.24 (0.29) | 4.18 (0.33) | 4.14 (0.38) | <0.001 |
| Serum glucose (mg/dL) | 98.76 (37.64) | 98.10 (38.70) | 96.60 (33.37) | 95.75 (31.93) | 98.46 (34.23) | 0.680 |
| Phosphorus (mg/dL) | 3.73 (0.55) | 3.69 (0.53) | 3.72 (0.52) | 3.76 (0.57) | 3.82 (0.57) | 0.006 |
| Uric acid (mg/dL) | 5.17 (1.48) | 5.19 (1.54) | 5.20 (1.40) | 5.14 (1.47) | 5.33 (1.62) | 0.383 |
| TIBC, Frozen serum (ug/dL) | 371.44 (72.17) | 367.11 (63.66) | 374.23 (64.47) | 376.02 (65.96) | 368.16 (75.14) | 0.254 |
| Mortality | <0.001 | |||||
| Alive | 387 (91.71%) | 408 (94.66%) | 401 (93.69%) | 410 (96.02%) | 379 (87.33%) | |
| Death | 35 (8.29%) | 23 (5.34%) | 27 (6.31%) | 17 (3.98%) | 55 (12.67%) | |
| Sex | 0.004 | |||||
| Female | 250 (59.24%) | 259 (60.09%) | 260 (60.75%) | 282 (66.04%) | 303 (69.82%) | |
| Male | 172 (40.76%) | 172 (39.91%) | 168 (39.25%) | 145 (33.96%) | 131 (30.18%) | |
| Hypertension | <0.001 | |||||
| No | 285 (67.54%) | 320 (74.25%) | 302 (70.56%) | 308 (72.13%) | 232 (53.46%) | |
| Yes | 129 (30.57%) | 109 (25.29%) | 124 (28.97%) | 119 (27.87%) | 201 (46.31%) | |
| No records | 8 (1.90%) | 2 (0.46%) | 2 (0.47%) | 0 (0.00%) | 1 (0.23%) | |
| Physical activity | 0.005 | |||||
| Sit during the day | 138 (32.70%) | 123 (28.54%) | 118 (27.57%) | 92 (21.55%) | 110 (25.35%) | |
| Stand/Walk a lot | 111 (26.30%) | 117 (27.15%) | 107 (25.00%) | 87 (20.37%) | 113 (26.04%) | |
| Light load/Climb stairs often | 54 (12.80%) | 66 (15.31%) | 60 (14.02%) | 76 (17.80%) | 70 (16.13%) | |
| Heavy work/load | 97 (22.99%) | 103 (23.90%) | 112 (26.17%) | 144 (33.72%) | 119 (27.42%) | |
| No records | 22 (5.21%) | 22 (5.10%) | 31 (7.24%) | 28 (6.56%) | 22 (5.07%) | |
| Race | <0.001 | |||||
| Black | 114 (27.01%) | 108 (25.06%) | 73 (17.06%) | 61 (14.29%) | 40 (9.22%) | |
| Mexican American | 106 (25.12%) | 104 (24.13%) | 101 (23.60%) | 97 (22.72%) | 48 (11.06%) | |
| Other Hispanic | 12 (2.84%) | 23 (5.34%) | 22 (5.14%) | 21 (4.92%) | 14 (3.23%) | |
| Other ethnicity | 190 (45.02%) | 196 (45.48%) | 232 (54.21%) | 248 (58.08%) | 332 (76.50%) | |
| Chronic kidney disease | 0.002 | |||||
| Stage2 | 10 (2.37%) | 14 (3.25%) | 3 (0.70%) | 3 (0.70%) | 1 (0.23%) | |
| Stage3 | 386 (91.47%) | 397 (92.11%) | 392 (91.59%) | 389 (91.10%) | 398 (91.71%) | |
| Stage4 | 23 (5.45%) | 18 (4.18%) | 26 (6.07%) | 25 (5.85%) | 25 (5.76%) | |
| Stage5 | 3 (0.71%) | 2 (0.46%) | 7 (1.64%) | 10 (2.34%) | 10 (2.30%) | |
Notes: Values are presented as mean (standard deviation) or median (minimum-maximal) for continuous variables, and as number (percentage) for categorical variables.
Abbreviations: BMI, body mass index; eGFR, estimated glomerular filtration rate; TIBC, total iron binding capacity.