Table 1 Multiple linear regression with fatigue (Functional Assessment of Chronic Illness Therapy—Fatigue (FACIT-F) score) as the dependent variable*
Significant independent variables†B (95% CI)βp Value
Model 1‡
    Anxiety (HADS)0.939 (0.407 to 1.471)0.3210.001
    Depression (HADS)0.908 (0.258 to 1.558)0.2670.007
    Motivation (item 4, UPDRS I)5.165 (1.779 to 8.552)0.2580.003
    Parkinsonism (UPDRS III total score)0.178 (0.031 to 0.325)0.1940.018Adjusted R2, final model: 0.482
    Pain (NHP-Pain)0.076 (0.005 to 0.146)0.1750.035
Model 2§
    Anxiety (HADS)0.783 (0.375 to 1.191)0.297<0.001
    Axial/postural/gait impairment (UPDRS III)0.811 (0.434 to 1.188)0.302<0.001
    Depression (HADS)0.837 (0.287 to 1.387)0.2530.003Adjusted R2, final model: 0.498
    Motivation (item 4, UPDRS I)4.277 (1.505 to 7.049)0.2200.003
  • *FACIT-F scores were reversed so that low scores indicate less fatigue. Significant predictors were identified by means of forward stepwise multiple regression (entry/removal criteria, p<0.05/p>0.10). Data were then reanalysed with only significant predictors entered as independent variables in a forced entry model.

  • †Listed by their relative predictive value (β).

  • ‡Independent variables: age (years), time since Parkinson disease diagnosis (years), daily pramipexole dose (mg), UPDRS III total score, MMSE score, ESS score, HADS depression score, HADS anxiety score, NHP-Pain score, PSQI global score, symptomatic orthostasis (item 42, UPDRS IV; 0 = no, 1 = yes), thought disorder (item 2, UPDRS I, dichotomised; 0 = no signs of thought disorder, 1 = signs of thought disorder (scores 1–4)), motivation (item 4, UPDRS I, dichotomised; 0 = normal motivation, 1 = impaired motivation (scores 1–4)).

  • §Independent variables as in model 1 but with axial/postural/gait impairment, resting tremor, action tremor, limb bradykinesia and rigidity scores entered instead of the total UPDRS motor score (see Methods).

  • β, standardised regression coefficient; B, regression coefficient; FACIT-F, Functional Assessment of Chronic Illness Therapy—Fatigue scale; HADS, Hospital Anxiety and Depression Scale; UPDRS, Unified Parkinson’s Disease Rating Scale; NHP, Nottingham Health Profile.