Table 3.

Potential predictors of neurometabolites estimated with separate mixed linear regression models for five different exposure settings. Statistically significant results are marked in bold.

	GABA [i.u.]		Glu [i.u.]		Glx [i.u.]		tCr [i.u.]		Cho [i.u.]		NAA [i.u.]		Total [iu.]	NAA	mI [i.u.]
	exp(β)	P value	exp(β)	P value	exp(β)	P value	exp(β)	P value	exp(β)	P value	exp(β)	P value	exp(β)	P value	exp(β)	P value
Model 1
Intercept	1.746		5.580		8.452		6.405		1.965		6.786		7.357		3.845
Active welders vs. controls	1.017	0.60	1.039	0.13	1.030	0.34	0.967	0.02	0.993	0.78	1.005	0.80	1.028	0.09	1.003	0.92
Former welders vs. controls	1.020	0.64	1.011	0.74	1.023	0.59	0.976	0.19	0.970	0.32	0.989	0.65	1.008	0.71	0.968	0.37
Parkinson patients vs. controls	1.020	0.53	0.996	0.88	1.021	0.51	0.969	0.03	1.023	0.36	0.983	0.38	0.986	0.39	1.017	0.55
Haemochromatosis patients vs. controls	1.025	0.62	0.936	0.09	0.989	0.83	0.940	0.005	0.969	0.38	0.963	0.18	0.975	0.31	0.994	0.88
Former vs. never smokers	0.984	0.56	1.034	0.13	1.057	0.04	1.019	0.14	1.031	0.15	1.005	0.74	1.020	0.17	1.062	0.02
Current vs. never smokers	0.967	0.27	0.977	0.33	0.988	0.69	1.000	1.00	0.993	0.74	0.972	0.11	0.978	0.15	1.004	0.88
CDT > 2.6% vs. ≤ 2.6%	0.990	0.84	0.958	0.29	0.914	0.08	0.971	0.20	0.957	0.26	0.942	0.05	0.948	0.04	1.063	0.19
Age [per 10 years]	1.012	0.47	0.980	0.11	0.957	0.007	0.987	0.06	0.990	0.42	0.989	0.24	0.990	0.21	1.009	0.51
Cerebrospinal fluid [%]	0.989	<0.001	0.993	<0.001	0.996	0.10	0.993	<0.001	0.996	0.01	0.990	<0.001	0.990	<0.001	0.993	<0.001
Striatum vs. thalamus	0.958	0.03	1.146	<0.001	1.261	<0.001	1.080	<0.001	1.011	0.35	0.909	<0.001	0.856	<0.001	0.914	<0.001
Model 2a
Mn in blood [log μg/L]	0.964	0.34	1.054	0.11	1.031	0.45	1.009	0.65	0.998	0.95	1.033	0.16	1.039	0.07	0.953	0.19
Serum ferritin [log μg/L]	1.005	0.68	1.001	0.91	0.996	0.78	0.992	0.18	1.001	0.95	0.980	0.005	0.991	0.17	1.010	0.39
Serum iron [log μg/dL]	1.015	0.61	1.009	0.70	1.045	0.14	1.000	0.98	0.997	0.90	1.045	0.009	1.035	0.02	0.994	0.83
Model 3a
R1, globus pallidus [log 1/ms]	0.829	0.11	0.850	0.08	0.845	0.14	0.867	0.005	0.835	0.04	0.887	0.07	0.920	0.16	0.957	0.66
R2*, globus pallidus [log 1/ms]	0.919	0.16	1.083	0.11	1.137	0.04	1.020	0.46	1.027	0.55	0.989	0.75	0.975	0.41	0.892	0.03
Model 4a
Respirable Mn [log μg/m3]	1.006	0.63	1.002	0.84	0.998	0.86	1.002	0.61	1.001	0.89	0.995	0.45	0.998	0.79	1.007	0.56
Model 5a
Respirable iron [log μg/m3]	1.006	0.52	0.997	0.68	0.990	0.35	1.000	0.98	0.997	0.65	0.993	0.17	0.995	0.25	1.008	0.36

Model 1: At-risk occupation or disease; Model 2: Systemic exposure; Model 3: Brain exposure; Model 4: Airborne exposure to Mn in active welders; Model 5: Airborne exposure to iron in active welders; GABA: γ-aminobutyric acid; Glu: glutamate; Glx: Glu and glutamine; tCr: total creatine; Cho: choline-containing compounds; NAA: N-acetylaspartate; mI: myo-inositol; Mn: manganese; CDT : Carbohydrate-deficient transferrin;

^aThese models are adjusted by age [10 years], smoking status (never, former, current), CDT (≤ 2.6%, > 2.6%), brain region (striatum, thalamus), cerebrospinal fluid [%], and hemisphere (left, right).