Table 1.
Baseline characteristics.
| Characteristics | Iron group (N = 203) | Placebo group (N = 202) |
|---|---|---|
| Female—no. (%) | 94 (46.3) | 93 (46.0) |
| Age—year | 42.1 ± 12.2 | 42.2 ± 12.3 |
| Blood donations in the past 2 years | 5.0 ± 1.9 | 5.3 ± 1.8 |
| Fatigue levela | 4.4 ± 2 | 4.6 ± 2 |
| Fatigue level ≥ 4—no. (%) | 116 (57.1) | 116 (57.4) |
| Multidimensional fatigue symptom inventoryb—total | 16.5 ± 15 | 16.1 ± 15 |
| MFSI—general | 10.7 ± 4 | 10.5 ± 4 |
| MFSI—physical | 8.3 ± 3 | 8.2 ± 3 |
| MFSI—emotional | 9.4 ± 3 | 9.0 ± 3 |
| MFSI—mental | 9.4 ± 3 | 9.4 ± 3 |
| MFSI—vigour | 21.5 ± 4 | 21.2 ± 4 |
| EQ-5Dc index | 9.2 ± 1 | 9.3 ± 1 |
| EQ-5D visual analog scale | 8.3 ± 1 | 8.4 ± 1 |
| 27-item symptom checklistd (SCL27) | 1.3 ± 0 | 1.3 ± 0 |
| Jenkins Sleep Scalee | 9.6 ± 3 | 9.0 ± 3 |
| Serum ferritin concentration at screening—µg/L | 28.0 ± 12.2 | 28.2 ± 11.8 |
| Serum ferritin concentration at baseline—µg/L | 18.5 ± 9.8 | 18.7 ± 10.4 |
| Ferritin < 25 µg/L at baseline—no. (%) | 165 (81.3) | 154 (76.6) |
| Ferritin < 15 µg/L at baseline—no. (%) | 89 (43.8) | 87 (43.3) |
| Hemoglobin concentration—g/L | 133.8 ± 14.6 | 134.0 ± 12.6 |
| Hemoglobin in males—g/L | 142.5 ± 10.2 | 140.5 ± 10.4 |
| Hemoglobin in females—g/L | 123.6 ± 12.1 | 126.4 ± 10.5 |
Plus–minus values are means ± SD. There were no significant differences in baseline characteristics between the two randomly assigned groups. Percentages may not total 100 because of rounding
aSelf-rated fatigue during the past 7 days on a numeric rating scale ranging from 1 (no fatigue at all) to 10 (extreme fatigue).
b30-item Multidimensional Fatigue Symptom Inventory-Short-Form (MFSI) measures general, physical, emotional, and mental fatigue, and vigour in the previous seven days. Each subscale comprises six items rated on a 5-point Likert scale from 0 (not at all) to 4 (extremely), yielding a total score between 0 and 24 for each subscale Total fatigue score is calculated by subtracting the vigour subscale score from the sum score of the other four subscales.
cEQ-5D is a generic instrument used to measure current health status related to mobility, self-care, usual activities, pain/discomfort and anxiety/depression. Each dimension is rated on three levels of perceived problems (with corresponding score): no problems (2), some or moderate problems (1), extreme problems (0), yielding a total standardized score between 0 and 10. Higher scores indicate better health status. The EQ-5D VAS allowed participants to rate their own health, ranging from 0 (worst imaginable health state) to 10 (best imaginable health state).
d27-item Symptom Checklist (SCL27) assesses general psychological distress based on depressive, anxiety, mistrust and vegetative symptoms in the previous week. Each item is rated on a 5-point Likert scale from 0 (not at all) to 4 (extremely). Total distress scores are expressed as the mean value of the 27 items.
e4-item Jenkins Sleep Questionnaire (JSQ) rates subjective sleep quality in the previous month, referring to trouble falling asleep, trouble staying asleep (waking up far too soon and inability to fall back to sleep), waking up several times per night, and waking up feeling tired and worn out after the usual amount of sleep. Response options (with corresponding score): not at all (0), 1–3 days (1), 4–7 days (2), 8–14 days (3), 15–21 days (4) and 22–31 days (5). Yields a total score between 0 to 20, with higher scores indicating poorer sleep quality.