Table 4.
Results from cognitive tests (raw scores) and the BRIEF (T scores): comparison of chronic fatigue group and CFS (CDC) subgroup versus healthy controls
| Cognitive measure | Mean values (SD) | Chronic fatigue group versus healthy controls | CFS (CDC) subgroup vs healthy controls | ||||||
|---|---|---|---|---|---|---|---|---|---|
| Chronic fatigue group N=120 | CFS (CDC) subgroup N=88 | Healthy controls N=39 | Difference (95% CI) | p Value | d* | Difference (95% CI) | p Value | d | |
| Processing speed | |||||||||
| CWIT condition 1+2 (s) | 30.9 (6.3) | 31.1 (6.5) | 27.5 (5.1) | 3.3 (1.1 to 5.5) | 0.003 | 0.58 | 3.5 (1.2 to 5.9) | 0.003 | 0.61 |
| Executive function | |||||||||
| Working memory (sum score) | 14.1 (3.4) | 13.7 (3.2) | 16.5 (3.8) | −2.4 (−3.7 to −1.1) | <0.001 | 0.67 | −2.7 (−4.1 to −1.5) | <0.001 | 0.8 |
| CWIT cognitive inhibition (s) | 59.7 (15.2) | 60.2 (15.9) | 53.5 (14.0) | 6.2 (0.8 to 11.7) | 0.025 | 0.43 | 6.6 (0.8 to 12.5) | 0.026 | 0.45 |
| CWIT cognitive inhibition (errors) | 2.0 (2.0) | 2.0 (2.1) | 1.6 (1.8) | 0.4 (−0.4 to 1.1) | 0.349 | 0.19 | 0.4 (−0.4 to 1.2) | 0.367 | 0.20 |
| CWIT cognitive flexibility (s) | 67.2 (15.2) | 66.1 (14.1) | 62.4 (13.8) | 4.8 (−0.8 to 10.4) | 0.092 | 0.42 | 3.7 (−1.6 to 9.1) | 0.167 | 0.27 |
| Verbal learning | |||||||||
| HVLT-R total recall (sum score) | 27.2 (4.1) | 27.3 (3.8) | 28.9 (3.7) | −1.7 (−3.2 to −0.3) | 0.022 | 0.44 | −1.6 (−3.1 to −0.2) | 0.026 | 0.44 |
| Verbal memory | |||||||||
| HVLT-R delayed recall (sum score) | 9.4 (2.1) | 9.5 (2.1) | 10.1 (1.7) | −0.6 (−1.4 to 0.1) | 0.119 | 0.33 | −0.6 (−1.4 to 0.2) | 0.119 | 0.31 |
| BRIEF† GEC | 55.1 (9.9) | 55.9 (10.1) | 43.8 (6.8) | 11.2 (8.2 to 14.3) | <0.001 | 1.34 | 12.1 (8.3 to 15.9) | <0.001 | 1.46 |
*d: Cohen's d, expressing effect size.
†BRIEF: Due to logistic problems, some BRIEF results were missing, giving a total of 32 completed responses for that inventory in the healthy controls group.
BRIEF, Behaviour Rating Inventory of Executive Function; CFS, Chronic Fatigue Syndrome; CDC, Centers for Disease Control and Prevention; CWIT, Color Word Interference Test; HVLT-R, Hopkins Verbal Learning Test-Revised; GEC, global executive composite.