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