Table 4.

Mediation models evaluating the effects of pigmented neuron density and tau burden on QSM through iron accumulation

	Ventromedial		Dorsomedial		Ventrolateral		Dorsolateral
	Estimate (CI)	P-value	Estimate (CI)	P-value	Estimate (CI)	P-value	Estimate (CI)	P-value
Predictor, pigmented neuron density
ACME (indirect effects via iron)	− 0.15 (− 0.30, − 0.03)	0.012	− 0.07 (− 0.19, 0.03)	0.18	− 0.13 (− 0.28, − 0.00)	0.046	− 0.14 (− 0.30, − 0.02)	0.026
Direct effects	0.14 (− 0.13, 0.41)	0.28	− 0.30 (− 0.53, − 0.06)	0.014	− 0.12 (− 0.35, 0.11)	0.25	− 0.13 (− 0.36, 0.11)	0.25
Total effect	− 0.01 (− 0.28, 0.27)	0.94	− 0.36 (− 0.61, − 0.11)	0.006	− 0.25 (− 0.50, − 0.00)	0.050	− 0.27 (− 0.52, − 0.01)	0.042
Proportion mediated via iron	0.44	0.93	0.17	0.18	0.51	0.080	0.52	0.056
Predictor, tau %AO
ACME (indirect effects via iron)	0.12 (0.001, 0.30)	0.046	0.16 (0.002, 0.37)	0.05	0.07 (− 0.13, 0.27)	0.53	0.07 (− 0.12, 0.28)	0.49
Direct effects	0.45 (0.10, 0.79)	0.018	0.15 (− 0.18, 0.47)	0.36	0.25 (− 0.05, 0.56)	0.1	0.15 (− 0.15, 0.46)	0.32
Total effect	0.57 (0.23, 0.92)	0.002	0.30 (− 0.04, 0.66)	0.098	0.32 (− 0.03, 0.68)	0.076	0.22 (− 0.13, 0.59)	0.23
Proportion mediated via iron	0.20	0.048	0.47	0.14	0.20	0.52	0.32	0.47

All variables were rank-transformed for analysis, with iron %AO as the mediator. Age and time from scan to death were included as covariates

Bold values indicate statistical significance at p < 0.05

ACME, average causal mediation effect; CI, confidence interval; %AO, percent area occupied; QSM, quantitative susceptibility mapping