Table 1 Demographics of the study population based on sex, age, fatigue severity scale scores, clinical assessments, blood tests and SF-36 test. HC, participants recruited as healthy controls; ME/CFSmm, participants recruited as mild/moderate ME/CFS patients; ME/CFSsa, participants recruited as severely affected ME/CFS patients. Body mass index (BMI); erythrocyte sedimentation rate (ESR); creatine phosphokinase (CPK); C-reactive protein (CRP). *p values were obtained as follows: χ² tests for categorical variables, Kruskal–Wallis test for non-normally distributed continuous variables and ANOVA test for normally distributed continuous variables. Normal distribution was checked by D’Agostino & Pearson test. Note that the median and interquantile for CRP were obtained from fitting a linear regression based on a truncated Lognormal distribution to the respective data.

Sex

Male

17

59

8

29

6

20

Female

12

41

20

71

24

80

 < 0.01

Age (years)

43

32–48

44

34–48

44

32–54

0.66

Fatigue severity scale scores

1.89

1.44–2.44

6.56

5.95–6.78

6.62

6.25–6.86

 < 0.0001

Clinical Assessments

Pulse oximetry (%)

99

98–99

98

97–98

99

98–99

0.03

Systolic pressure (mmHg)

126

111–131

124

110–136

120

108–129

0.48

Diastolic pressure (mmHg)

74

72–83

81

73–92

80

71–85

0.06

Height (cm)

171

168–175

168

162–178

165

159–177

0.31

Weight (kg)

80

66–86

74

63–86

63

54–81

0.06

BMI (kg/m²)

24

22–30

26

23–28

22

20–27

0.21

Waist circumference (cm)

90

78–102

91

87–100

79

72–90

0.01

Body fat

20

15–28

31

25–38

31

22–36

0.02

Body muscle

56

46–64

47

42–56

43

38–53

0.001

Body metabolic rate

1737

1469–1953

1509

1383–1685

1415

1197–1576

0.004

Pain analog scale

0.2

0.0–1.1

2.5

1.6–3.5

4.4

2.0–6.5

 < 0.0001

Fatigue analog scale

0.8

0.0–1.7

5.2

3.6–6.9

7.1

6.0–8.2

 < 0.0001

Blood tests

Hemoglobin (g/L)

144

131–151

140

130–144

141

131–148

0.64

White blood cells (10⁹/L)

5.75

4.73–6.60

6.56

5.75–7.90

5.96

5.28–7.37

0.15

Platelets (10⁹/L)

227

203–280

274

231–336

264

221–297

0.03

Red blood cells (10¹²/L)

4.83

4.50–5.02

4.67

4.34–4.94

4.64

4.39–4.89

0.62

Hematocrit

0.430

0.400–0.454

0.427

0.388–0.449

0.422

0.395–0.439

0.89

Neutrophils (10⁹/L)

3.21

2.54–4.08

3.97

2.92

5.28

3.00–4.59

0.18

Lymphocytes (10⁹/L)

1.85

1.65–2.10

1.70

1.60–2.29

1.93

1.55–2.32

0.84

Monocytes (10⁹/L)

0.45

0.36–0.51

0.51

0.41–0.60

0.43

0.40–0.54

0.21

Eosinophils (10⁹/L)

0.12

0.08–0.17

0.13

0.07–0.22

0.14

0.08–0.19

0.93

Basophils (10⁹/L)

0.04

0.03–0.04

0.05

0.03–0.06

0.05

0.03–0.06

0.04

ESR (mm/h)

2.00

2–5

5

2–12

5

2–8

0.01

Creatinine (μmol/L)

86

75–93

75

68–79

69

59–76

0.01

CPK (U/L)

108

83–220

79

62–101

64

50–76

 < 0.0001

CRP (CRP)

1.00

0.40–2.49

1.13

0.46–2.81

0.55

0.22–1.36

0.31

SF-36 test

Physical functioning

57.5

57.1–57.5

32.7

28.8–37.5

21.2

19.3–25.0

 < 0.0001

Role physical

57.2

54.4–57.2

28.0

22.4–33.6

21.2

21.2–25.7

 < 0.0001

Bodily Pain

55.6

51.5–62.0

42.2

34.2–44.7

34.2

26.5–42.2

 < 0.0001

General health

60.3

57.4–63.1

30.8

26.1–33.2

28.5

23.7–30.8

 < 0.0001

Vitality

52.6

48.9–58.5

28.8

25.9–33.3

25.9

22.9–31.8

 < 0.0001

Social functioning

57.3

57.3–57.3

27.2

19.7–32.3

17.2

17.2–22-3

 < 0.0001

Role emotional

56.2

56.2–56.2

45.7

35.3–52.7

56.2

38.8–56.2

 < 0.001

Mental health

54.8

48.3–58.7

40.4

36.5–48.3

48.3

40.4–53.5

 < 0.001

Physical component summary

58.4

55–7-59.8

29.4

26.5–33.9

19.9

16.8–23.1

 < 0.0001

Mental health component summary

54.2

47.8–57.1

41.8

34.4–45.0

45.9

43.6–50.4

 < 0.0001