Table. Group Differences in FA Slopes Between Age- and Sex-Matched No-to-Low and Heavy Drinkers and Age-Alcohol Interaction in the 2 Matched Cohorts.

Region name	Alcohol outcome (group difference)						Age-alcohol interaction (GLM), P value (n = 156)
	Matched all (N = 156)		Matched young (n = 78)		Matched old (n = 78)
	P value	Cohen d (95% CI)	P value	Cohen d (95% CI)	P value	Cohen d (95% CI)
Commissural tracts	.003a	0.47 (0.0004 to 0.0021)	<.001a	0.76 (0.0009 to 0.0031)	.60	0.16 (−0.0008 to 0.0016)	.008b
Genu	.01a	0.40 (0.0004 to 0.0027)	<.001a	0.75 (0.0013 to 0.0047)	.77	−0.07 (−0.0018 to 0.0013)	.009b
Body	.001a	0.51 (0.0004 to 0.0017)	.001a	0.73 (0.0006 to 0.0022)	.15	0.35 (−0.0003 to 0.0017)	.006b
Tapetum	.79	−0.04 (−0.0010 to 0.0008)	.74	0.07 (−0.0010 to 0.0014)	.39	−0.21 (−0.0020 to 0.0007)	.17
Splenium	.25	0.18 (−0.0005 to 0.0018)	.20	0.27 (−0.0006 to 0.0028)	.74	0.08 (−0.0016 to 0.0023)	.65
Corticospinal tracts	.02a	0.37 (0.0002 to 0.0018)	.007a	0.60 (0.0004 to 0.0026)	.54	0.15 (−0.0008 to 0.0016)	.01b
Fasciculi	.04a	0.33 (0.0001 to 0.0018)	.006a	0.61 (0.0005 to 0.0029)	.96	0.01 (−0.0011 to 0.0012)	.01b
Brainstem tracts	.15	0.23 (−0.0003 to 0.0021)	.06	0.44 (0 to 0.0032)	.97	−0.006 (−0.0020 to 0.0019)	.07
Limbic tracts	.06	0.31 (0 to 0.0019)	.12	0.34 (−0.0002 to 0.0024)	.22	0.29 (−0.0005 to 0.0022)	.32

Abbreviations: FA, fractional anisotropy; GLM, general linear model.

^aTwo-tailed 2-sample t test P < .05 (heavy drinkers having more negative slopes than no-to-low drinkers).

^bTwo-tailed age-drinking-group interaction P < .05 (heavy drinkers having more negative slopes than no-to-low drinkers at a younger age).