. Author manuscript; available in PMC: 2019 Oct 7.

Published in final edited form as: J Neuroimaging. 2019 Jun 7;29(5):624–629. doi: 10.1111/jon.12642

Table 2.

Annual change of metabolite ratios on flex point models in converters with MAPT mutations.

	NAA/Cr	mI/Cr	NAA/mI
	Estimates (95% CI)	Estimates (95% CI)	Estimates (95% CI)
Intercept	1.66 (1.60, 1.72)^***	0.49 (0.46, 0.53)^***	3.37 (3.14, 3.62)^***
Overall slope	−0.0003 (−0.01, 0.01)	−0.007 (−0.01, −0.002)^*	0.04 (0.003, 0.08)^*
Slope modifier after the flex point	−0.02 (−0.04, 0.006)	0.02 (0.006, 0.03)^*	−0.10 (−0.18, −0.02)^*
Flex point dummy variable	−0.03 (−0.08, 0.03)	0.04 (0.01, 0.07)^**	−0.30 (−0.50, −0.10)^**

This flex point was estimated in the models using a dummy variable to shift the estimated line with the second slope up or down, thereby moving the flex point left or right. The specific coding in our models estimated a slope over the entire time, and then a modifier to the slope after the flex point. The mixed models used random intercepts to account for within-subject repeated measures correlations nested in within-family correlations.

p<0.05;

^**

p<0.01;

^***

p<0.001;

CI = confidence interval; Abbreviations: NAA = N-acetylaspartate; Cr = creatine; mI = myo-inositol.