Table 3.

Comparison of predictive performance in brain age prediction by the number of PCA components retained on the internal test set.

Explained variance	Data	sMRI		FA		sMRI+FA
		MAE	r	MAE	r	MAE	r
20%	Train	3.632	0.956	5.687	0.894	2.859	0.972
	Test	3.733	0.952	5.971	0.879	3.282	0.957
40%	Train	2.673	0.977	3.090	0.969	2.146	0.984
	Test	3.242	0.964	3.920	0.947	2.778	0.970
60%	Train	2.050	0.986	2.425	0.980	1.695	0.990
	Test	2.985	0.969	3.570	0.939	2.675	0.974
80%	Train	1.469	0.992	1.564	0.991	1.178	0.995
	Test	2.887	0.971	3.417	0.950	2.755	0.972
90%	Train	1.059	0.996	1.101	0.995	0.837	0.997
	Test	2.839	0.971	3.337	0.952	2.738	0.972

The best results are marked in bold.