Table 4.

Results from the simultaneous models, after variable selection by elastic net

Outcome type	Predictor	Association with brain outcomes
		Grey matter volume			Normal-appearing white matter volume			White matter hyperintensity volume			General fractional anisotropy			General mean diffusivity
		β	SE	p	β	SE	p	β	SE	p	β	SE	p	β	SE	p
Brain baseline level	Sex (male)	0.609	0.026	<0.001†	0.576	0.033	<0.001†							0.078	0.047	0.098
	Physical fitness	0.042	0.056	0.457	0.019	0.066	0.768	0.144	0.066	0.029 †	0.180	0.069	0.009 †	0.181	0.074	0.015 †
	Allostatic load	−0.174	0.044	<0.001 †	−0.101	0.048	0.035				−0.095	0.053	0.072
	Health conditions	−0.059	0.035	0.094	−0.029	0.040	0.466				−0.100	0.042	0.017 †
	SES	0.054	0.055	0.330	0.173	0.059	0.004†				0.047	0.068	0.489
	Prior intelligence	0.164	0.037	<0.001 †	0.116	0.047	0.013 †				0.094	0.052	0.069
	Education				0.002	0.046	0.966				− 0.138	0.050	0.006 †
	Alcohol consump				− 0.065	0.041	0.117
	APOE e4 genotype	0.059	0.032	0.066	0.074	0.037	0.043
	Polygenic SCZ risk	0.022	0.032	0.505	0.068	0.037	0.067
Brain change	Sex (male)	−0.199	0.049	<0.001 †	0.090	0.052	0.084
	Physical fitness				0.259	0.096	0.007 †	−0.065	0.077	0.396				0.346	0.103	0.001 †
	Allostatic load	0.103	0.059	0.083	0.107	0.063	0.091
	Health conditions				−0.009	0.055	0.870							−0.114	0.059	0.055
	SES				0.132	0.072	0.068
	Education							0.032	0.037	0.389
	Smoking
	Alcohol consump							−0.108	0.038	0.004†
	APOE e4 genotype				−0.152	0.050	0.002 †	−0.080	0.035	0.023
	Polygenic SCZ risk				−0.099	0.052	0.055	−0.039	0.037	0.290				−0.120	0.059	0.041

Blank cells indicate variables that were not selected for the relevant brain outcome. Bold values are statistically significant. All brain outcomes scored such that positive associations indicate links to healthier ageing, and negative associations indicate links to unhealthy ageing

Variables not selected for inclusion in the models for any brain outcome were smoking (for brain baseline levels) and intelligence (for brain changes). p-values shown uncorrected; those values that survived per-outcome False Discovery Rate correction are indicated with a ^† symbol

SCZ schizophrenia; SES socioeconomic status; β standardized beta