Table 1.
Outcome of cognitive tasks and scales. Mean number of correct results, processing time and intra-individual percentual changes versus baseline (6 p.m.) after creatine or placebo. Changes in Karolinska Sleepiness Scale (KSS) and Fatigue scale before (bef.) and after (aft.) each session are shown below. WMT, Word memory test. Data are given ± SD.
| Task | No. of trials | Number of correct results (score) | ||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 6 p.m. | 0 a.m. | 2 a.m. | 4 a.m. | |||||||||||||
| Placebo | Creatine | Placebo | Creatine | Placebo | Creatine | Placebo | Creatine | |||||||||
| WMT | 22 | 18.1 ± 3 | 16.7 ± 4.2 | 17.0 ± 3.0 | 17.4 ± 2.8 | 16.4 ± 3.4 | 18.1 ± 2.9 | 16.6 ± 4.0 | 16 ± 4 | |||||||
| vs. 6 p.m. (%) | − 5.9% | 3.9% | − 9.1%+ | 8.2% | − 8.3%+ | − 3.9% | ||||||||||
| Digit span | 12 | 8.9 ± 2.6 | 8.9 ± 2.2 | 8.0 ± 2.6 | 7.4 ± 2.1 | 6.7 ± 2.5 | 9.0 ± 2.2 | 7.1 ± 2.3 | 7.2 ± 2.7 | |||||||
| vs. 6 p.m. (%) | − 10.4% | − 16.9% | − 24.8%+ | 1.6% | − 20.8%+ | − 18.5% | ||||||||||
| N-back | 13.8 (6–30) | 14.2/6.9 | 4.3/7.5 | 4.4/6.3 | 4/6.6 | 4.7/7.0 | 4.7/7.3 | 4.7/7.1 | 4.5/7.3 | |||||||
| vs. 6 p.m. (%) | 12 ± 28% | 9 ± 26% | 4 ± 24% | 14 ± 28% | 13 ± 25% | 10 ± 39% | ||||||||||
| Language | 21 | 16.6 ± 2 | 17.1 ± 1.7 | 17.3 ± 2.3 | 18.3 ± 1.9 | 17.6 ± 2.2 | 17.3 ± 1.7 | 17.3 ± 1.7 | 18.2 ± 1.8 | |||||||
| vs. 6 p.m. (%) | 4.0% | 7.8%+ | 6.0% | 2.0% | 4.0% | 7.1%+ | ||||||||||
| Logic | 17 | 14.5 ± 1 | 13.6 ± 2.5 | 14.4 ± 1.3 | 14.5 ± 1.7 | 14.9 ± 1.2 | 14.3 ± 1.5 | 13.7 ± 1.7 | 14.2 ± 1.2 | |||||||
| vs. 6 p.m. (%) | − 0.9% | 6.4% | 2.3% | 4.9% | − 5.5% | 4.4% | ||||||||||
| Numeric | 8 | 6.5 ± 1 | 6.7 ± 1.6 | 6.9 ± 1.1 | 7.4 ± 1.1 | 7.3 ± 1.2 | 7.7 ± 0.9 | 6.6 ± 1.7 | 7.1 ± 1.3 | |||||||
| vs. 6 p.m. (%) | 6.1% | 9.9% | 11.2% | 13.9%+ | 1.0% | 5.0% | ||||||||||
| Task | No. of trials | Processing time (t) | ||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 6 p.m. | 0 a.m. | 2 a.m. | 4 a.m. | |||||||||||||
| Placebo | Creatine | Placebo | Creatine | Placebo | Creatine | Placebo | Creatine | |||||||||
| WMT | 22 | 101 ± 37 s | 112 ± 42 s | 107 ± 26 s | 100 ± 25 s | 116 ± 36 s | 101 ± 27 s | 98 ± 22 s | 99 ± 42 s | |||||||
| vs. 6 p.m. (%) | 5.7% | − 10.3% | 15.1% | − 10.8% | − 2.6% | − 12.9% | ||||||||||
| Digit SPAN | 12 | 26.8 ± 10 s | 30.2 ± 8 s | 31.2 ± 13 s | 34.6 ± 20 s | 27.3 ± 7 s | 28.4 ± 10 s | 30.2 ± 10 s | 27.0 ± 15 s | |||||||
| vs. 6 p.m. (%) | 16.5% | 14.3% | 2.0% | − 6.0% | 12.7% | − 10.6% | ||||||||||
| Language | 21 | 137 ± 35s | 165 ± 32 s | 161 ± 33 s | 139 ± 33 s | 162 ± 35 s | 150 ± 31 s | 159 ± 34 s | 152 ± 31 s | |||||||
| vs. 6 p.m. (%) | 17.5%+ | − 15.6%+ | 18.7%+ | − 8.7% | 16.0%+ | − 7.5% | ||||||||||
| Logic | 17 | 214 ± 63 s | 227 ± 60s | 219 ± 54 s | 198 ± 52 s | 214 ± 54 s | 193 ± 46 s | 214 ± 52 s | 196 ± 45 | |||||||
| vs. 6 p.m. (%) | 2.4% | − 13%+ | 0.2% | − 15%+ | 0.2% | − 14%+ | ||||||||||
| Numeric | 8 | 127 ± 37 s | 147 ± 27 s | 126 ± 34 s | 111 ± 25 s | 131 ± 28 s | 121 ± 23 s | 139 ± 38 s | 128 ± 33 s | |||||||
| vs. 6 p.m. (%) | − 0.4% | − 24% ** | 3.4% | − 18% + | 9.6% | − 13%+ | ||||||||||
| Karolinska Sleepiness Scale (KSS)a | ||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 6 p.m. | 0 a.m. | 2 a.m. | 4 a.m. | |||||||||||||
| Placebo | Creatine | Placebo | Creatine | Placebo | Creatine | Placebo | Creatine | |||||||||
| bef. | aft. | bef. | aft. | bef. | aft. | bef. | aft. | bef. | aft. | bef. | aft. | bef. | aft. | bef. | aft. | |
| Score | 2.7 | 2.7 | 3.1 | 3.1 | 6.1 | 5.9 | 5.8 | 5.8 | 6.8 | 6.8 | 7.1 | 6.9 | 7.4 | 7.4 | 7.8 | 7.5 |
| aft vs. bef | 0 | 0.07 | − 0.2 | 0 | 0 | 0.28 | − 0.1 | 0.33* | ||||||||
| vs. 6 p.m. (%) | 122%*** | 92%*** | 150%*** | 128%*** | 172%*** | 145%*** | ||||||||||
| Inverted Samn & Perelli Fatigue score (FAT)b | ||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 6 p.m. | 11 p.m. | 2 a.m. | 4 a.m. | |||||||||||||
| Placebo | Creatine | Placebo | Creatine | Placebo | Creatine | Placebo | Creatine | |||||||||
| bef. | aft. | bef. | aft. | bef. | aft. | bef. | aft. | bef. | aft. | bef. | aft. | bef. | aft. | bef. | aft. | |
| Score | 6.4 | 6.6 | 6.5 | 6.6 | 10.7 | 10.5 | 10.9 | 10.7 | 13.8 | 14.1 | 13.2 | 12.4 | 15.7 | 15.6 | 14.9 | 14.2 |
| aft vs. bef | 0.1 | 0.1 | − 0.2 | − 0.1 | 0.4 | − 0.8 | − 0.1 | − 0.6 | ||||||||
| vs. 6 p.m. (%) | 63%** | 65%** | 115%*** | 96%** | 141%*** | 122%** | ||||||||||
aCorrect/total trials; bscales acquired before and after passing the battery of 7 tests *p = values of p ≤ 0.005, **p = values of p ≤ 0.0005, *** p = values of p ≤ 0.00005,+p = values of 0.0063 ≤ p ≤ 0.05, that did not survive Bonferroni correction.