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Table 1 Canonical loadings for the fatigue (criterion) and quality of life (predictor) in the Parkinson group

From: The dimensionality of fatigue in Parkinson’s disease

Variables

Mean (SD)

Range

Loadings

Predictor variables (quality of life)

 1. PD Quality of Life Questionnaire Summary Index, PDQ-39SI

27 (20)

4–65

0.82

 2. Non-Motor Symptoms Questionnaire, NMS-Q

12 (6)

1–21

0.73

 3. Hospital Anxiety and Depression Scale, HADS

12 (7)

3–24

0.71

 4. Non-Motor Symptoms Scale, NMSS

66 (44)

5–190

0.67

 5. Unified Parkinson’s Disease Rating Scale Total, UPDRS

43 (14)

20–73

0.66

 6. Duration of disease (years)

8 (5)

1–22

0.46

 7. Epworth Sleepiness Scale, ESS

8 (4)

1–15

0.40

 8. Age at diagnosis (years)

63 (9)

45–79

0.38

 9. Body mass index, BMI

27 (7)

17–54

− 0.18

 10. Life orientation test, LOT-R

17 (5)

5–24

− 0.40

 11. Montreal Cognitive Assessment, MoCA

26 (4)

15–30

− 0.52

 12. PD sleep Scale

100 (26)

42–144

− 0.53

 13. EPIC Physical Activity Questionnaire, ePAQ

72 (68)

8–318

− 0.43

Criterion variables (Fatigue)

 1. Fatigue Severity Scale, FSS

38 (15)

11–60

0.86

 2. Functional Assessment of Chronic Illness Therapy Fatigue Scale, FACIT-F

32 (12)

14–50

− 0.83

 3. Parkinson Fatigue Scale, PFS

50 (17)

17–77

0.80

 4. Visual Analog Fatigue Scale, VAFS

6 (2)

2–10

− 0.69

  1. All quality of life variables except body mass index reliably predicted perception of fatigue in Parkinson’s disease. The PDQ-39SI produced the strongest prediction