Table 3.

Rank regression analysis for substantia nigra susceptibility as the outcome

	QSM
	Ventromedial		Dorsomedial		Ventrolateral		Dorsolateral
	Estimate (SE)	P-value	Estimate (SE)	P-value	Estimate (SE)	P-value	Estimate (SE)	P-value
Model 1
Iron %AO	1.057 (0.268)	< 0.001	0.425 (0.127)	0.002	0.548 (0.122)	< 0.001	0.543 (0.124)	< 0.001
Pigmented neuron density	0.598 (0.227)	0.011	− 0.297 (0.122)	0.019	− 0.121 (0.117)	0.3	− 0.126 (0.119)	0.3
Interaction: Iron × pigmented neuron	− 1.018 (0.007)	0.017
Model 2
Iron %AO	0.433 (0.136)	0.002	0.483 (0.132)	< 0.001	0.579 (0.119)	< 0.001	0.593 (0.122)	< 0.001
Non-pigmented neuron density	0.051 (0.128)	0.69	0.096 (0.129)	0.46	0.016 (0.118)	0.89	− 0.074 (0.116)	0.53
Model 3
Tau %AO	0.448 (0.177)	0.015	0.147 (0.168)	0.39	0.254 (0.158)	0.12	0.149 (0.157)	0.35
Iron %AO	0.348 (0.151)	0.026	0.502 (0.143)	0.001	0.563 (0.128)	< 0.001	0.601 (0.130)	< 0.001

These variables are analyzed on the ranks. The results for the final two predictor models with adjustments for rank age and rank time from scan to death. If an interaction was not significant, it was removed, and the results of the two main effects are shown

Bold values indicate statistical significance at p < 0.05

%AO, percent area occupied; QSM, quantitative susceptibility mapping; SE, standard error