Demographic and clinical characteristics of the study participants
| Characteristics | Mean values | Group comparisons (p value) | |||
|---|---|---|---|---|---|
| Chronic fatigue group N=120 | CFS (CDC) subgroup N=88 | Healthy controls N=39 | Chronic fatigue group versus healthy controls | CFS (CDC) subgroup versus healthy controls | |
| Gender | |||||
| Female (%) | 86 (72) | 64 (72) | 28 (72) | 0.98 | 0.91 |
| Age | |||||
| Mean (SD) | 15.4 (1.6) | 15.3 (1.6) | 15.2 (1.6) | 0.57 | 0.79 |
| Age range, years | 12–18 | 12–18 | 12–18 | ||
| BMI | |||||
| Mean (SD, Z score) | 21.5 (4.2, 0.4) | 21.2 (4.2, 0.3) | 20.3 (2.9) | 0.04 | 0.14 |
| CDC criteria fulfilled (%) | 88 (73) | NA | |||
| NICE criteria fulfilled (%) | 107 (89) | NA | |||
| MFQ | |||||
| Mean (SD) | 17.2 (10.1) | 18.7 (10.4) | 6.6 (7.8) | <0.001 | <0.001 |
| Disease duration months (range) | 21.4 (4–104) | 21.1 (6–104) | NA | NA | NA |
| CFQ | |||||
| Mean (SD) | 19.2 (6.2) | 19.9 (6.0) | 8.9 (4.5) | <0.001 | <0.001 |
| School absence | |||||
| Mean % (SD) | 65 (30) | 66 (30) | 2 (7) | <0.001 | <0.001 |
| STAI-T | |||||
| Mean (SD) | 42.8 (9.0) | 44.0 (9.1) | 32.1 (7.25) | <0.001 | <0.001 |
| KSQ | |||||
| Mean (SD) | 3.4 (0.97) | 3.3 (0.9) | 4.9 (0.86) | <0.001 | <0.001 |
CFS (CDC) subgroup: Participant subgroup that meets the CDC criteria for chronic fatigue syndrome; School absence: the percentage of days out of school during the last month (20 days/month is 100%).
BMI, body mass index; CDC, Centers for Disease Control and Prevention; CFS, chronic fatigue syndrome; CFQ, Chalder Fatigue Questionnaire; KSQ, Karolinska Sleep Questionnaire; MFQ, Mood and Feelings Questionnaire; NICE, National Institute for Health and Care Excellence; STAI-T, Spielberger State-Trait Inventory.