Table 5

Stepwise linear regression analysis of the MDS-UPDRS part II

	Standardised regression coefficient	SE	p Value
HY stage	0.143	0.556	0.0011
Number of sleep-related symptoms	0.226	0.293	<0.0001
Disease duration	0.193	0.073	<0.0001
MDS-UPDRS part III	0.264	0.028	<0.0001
TD/PIGD ratio	−0.208	0.162	<0.0001
Depression	0.117	0.920	0.0012
MDS-UPDRS part IV	0.109	0.108	0.0085

Final model, adjusted R²=0.539.
Dependent variables; age, sex, HY stage, disease duration, MMSE, MDS-UPDRS III, IV, number of sleep-related symptoms (0–3; EDS, PD-SP and pRBD), depression and TD/PIGD ratio.
HY, Hoehn and Yahr stage; MDS-UPDRS, Movement Disorder Society revision of the Unified Parkinson’s Disease Rating Scale; TD, tremor dominant; PIGD, postural instability and gait disturbance.