Table 1. Baseline Characteristics.
| Characteristics | Participants by iron dosage, No (%) (N = 71 677) | P value | ||
|---|---|---|---|---|
| Daily (n = 26 982) | Multiple doses per day (n = 43 552) | Alternate day dose (n = 1143) | ||
| Cohort with normal kidney function (N = 47 201)a | ||||
| Participants | 17 071 (63.3) | 29 433 (67.6) | 697 (61.0) | NA |
| Sex | ||||
| Male | 14 322 (83.9) | 24 935 (84.7) | 601 (86.2) | .03 |
| Female | 2749 (16.1) | 4498 (15.3) | 96 (13.8) | |
| Age >60 y | 12 511 (73.3) | 20 678 (70.3) | 548 (78.6) | <.001 |
| Body mass index >25b | 12 437 (72.9) | 22 240 (75.6) | 514 (73.7) | <.001 |
| CCI score >3 | 4846 (28.4) | 7433 (25.3) | 260 (37.3) | <.001 |
| ACE-I or ARB | 7467 (43.7) | 13 027 (44.3) | 296 (42.5) | .39 |
| PPI | 5432 (31.8) | 9851 (33.5) | 222 (31.9) | .001 |
| Anticoagulant | 4017 (23.5) | 5754 (19.5) | 182 (26.1) | <.001 |
| Antiplatelet | 4092 (24.0) | 6265 (21.3) | 184 (26.4) | <.001 |
| Iron formulation: ferrous sulfate | 14 156 (82.9) | 24 888 (84.6) | 605 (86.8) | <.001 |
| Diabetes | 7996 (46.8) | 13 244 (45.0) | 334 (47.9) | <.001 |
| COPD | 5209 (30.5) | 8219 (27.9) | 218 (31.3) | <.001 |
| Heart failure | 4692 (27.5) | 8005 (27.2) | 160 (23.0) | .03 |
| Sleep apnea | 3277 (19.2) | 4521 (15.4) | 211 (30.3) | <.001 |
| Current or former smoker | 8902 (52.1) | 15 101 (51.3) | 396 (56.8) | .005 |
| Cohort with CKD (N = 24 476)a | ||||
| Participants | 9911 (36.7) | 14 119 (32.4) | 446 (39.0) | NA |
| Sex | ||||
| Male | 9445 (95.3) | 13 473 (95.4) | 426 (95.5) | .89 |
| Female | 466 (4.7) | 646 (4.6) | 20 (4.5) | |
| Age >60 y | 9234 (93.1) | 12 887 (91.3) | 417 (93.5) | <.001 |
| Body mass index >25b | 7305 (73.8) | 10 810 (76.6) | 331 (74.2) | <.001 |
| CCI score >3 | 5996 (60.5) | 8107 (57.4) | 296 (66.4) | <.001 |
| CKD Stage | ||||
| 3A and 3B | 8433 (85.1) | 12 060 (85.4) | 361 (80.9) | .03 |
| 4 | 1478 (14.9) | 2059 (14.6) | 85 (19.1) | |
| ACE-I or ARB | 5171 (52.2) | 7689 (54.5) | 227 (50.9) | .001 |
| PPI | 2871 (29.0) | 4166 (29.5) | 127 (28.5) | .62 |
| Anticoagulant | 3219 (32.5) | 4202 (29.8) | 149 (33.4) | <.001 |
| Antiplatelet | 3116 (31.4) | 3937 (27.9) | 152 (34.1) | <.001 |
| Iron formulation: ferrous sulfate | 8189 (82.6) | 11 747 (83.2) | 398 (89.2) | .001 |
| Diabetes | 5968 (60.2) | 8553 (60.6) | 273 (61.2) | .81 |
| COPD | 3443 (34.7) | 4681 (33.2) | 138 (30.9) | .02 |
| Heart failure | 4665 (47.1) | 6759 (47.9) | 198 (44.4) | .20 |
| Sleep apnea | 2002 (20.2) | 2532 (17.9) | 131 (29.4) | <.001 |
| Current or former smoker | 4824 (48.7) | 7010 (49.6) | 253 (56.7) | .002 |
Abbreviations: ACE-I, angiotensin converting enzyme inhibitors; ARB, angiotensin receptor blockers; CCI, Charlson Comorbidity Index; CKD, chronic kidney disease; COPD, chronic obstructive pulmonary disease; NA, not applicable; PPI, proton-pump inhibitors.
a
Percentages in the participants rows are based on totals in each iron dosage group. All other percentages are based on the totals in the participants rows for the 2 cohorts.
b
Body mass index was calculated as weight in kilograms divided by height in meters squared and contained missing values (21 for the cohort with normal kidney function and 11 for the cohort with CKD). Only complete cases were considered.