Age-Associated Reduction of Asymmetry in Human Central Auditory Function: A 1H-Magnetic Resonance Spectroscopy Study

Table 1

Comparison of central auditory function between the young and older groups before and after pure tone stimulation.

Variable	Young (𝑁=10)	Older (𝑁=8)	𝑃 value
Left-NAA/Cr
Before	2.95 (2.75, 2.97)	1.90 (1.90, 1.96)	<0.001*
After	3.02 (2.96, 3.05)	1.80 (1.64, 1.98)	<0.001*
Adjusted difference^a	reference	−1.189 (−1.730, −0.648)	<0.001*
Right-NAA/Cr
Before	2.78 (2.75, 2.92)	1.88 (1.83, 1.94)	<0.001*
After	2.87 (2.85, 2.92)^†	1.98 (1.89, 2.01)	<0.001*
Adjusted difference^a	reference	−1.109 (−1.518, −0.699)	<0.001*
Left-Glx/Cr
Before	0.12 (0.11, 0.13)	0.11 (0.10, 0.12)	0.657
After	0.06 (0.05, 0.07)	0.10 (0.09, 0.11)	<0.001*
Adjusted difference^a	reference	0.040 (0.030, 0.051)	<0.001*
Right-Glx/Cr
Before	0.09 (0.08, 0.10)	0.11 (0.11, 0.12)	0.037*
After	0.11 (0.10, 0.35)^†	0.12 (0.12, 0.14)^†	0.168
Adjusted difference^a	reference	−0.047 (−0.141, 0.048)	0.311
Left-GABA/Cr
Before	0.12 (0.11, 0.14)	0.07 (0.06, 0.33)	0.083
After	0.14 (0.13, 0.16)	0.08 (0.07, 0.08)	0.007*
Adjusted difference^a	reference	−0.067 (−0.171, 0.037)	0.187
Right-GABA/Cr
Before	0.10 (0.09, 0.11)†	0.07 (0.06, 0.08)	0.001*
After	0.07 (0.06, 0.07)^†	0.05 (0.05, 0.06)^†	0.023*
Adjusted difference^a	reference	−0.010 (−0.023, 0.003)	0.126

Data are presented as median (interquartile range, the range between the 25th and 75th percentile) and were compared between groups by Mann-Whitney 𝑈 test. Data were compared within groups between left and right by Wilcoxon signed rank test used.
Abbreviations: Cr: creatine-containing compounds; GABA: γ-amino butyric acid; Glx: glutamine/glutamate; NAA: N-acetyl-aspartate.
^aCompared with the young group, the adjusted difference of older group is presented as difference and 95% CI. After Adjusting for before-stimulation variables, after-stimulation variables were compared between groups by analysis of covariance.
*Indicates a significant between-group difference (𝑃<0.05).
^†Indicates a significant within-group difference between left and right (𝑃<0.05).