Table 2.
LMM analysis of dACC neurometabolite levels (mean ± sd).
| Nonsmoking | Smoking | |||
|---|---|---|---|---|
| Time 1 | Time 2 | Time 1 | Time 2 | |
| N | 35 | 19 | 49 | 41 |
| gray matter (volume %) | 51.5 ± 5.9 | 53.8 ± 6.2 | 52.5 ± 4.9 | 52.1 ± 5.6 |
| white matter (volume %) | 35.9 ± 6.9 | 31.6 ± 5.2 | 34.5 ± 6.2 | 34.9 ± 7.4 |
| CSF (volume %) | 11.9 ± 4.0 | 13.5 ± 4.1 | 12.9 ± 5.4 | 13.0 ± 4.6 |
| NAA (IU) | 21.3 ± 2.1 | 20.5 ± 2.2 | 23.8 ± 2.8a | 23.4 ± 3.0a |
| CRLB (%SD) | 4.2 ± 0.8 | 4.4 ± 0.9 | 4.7 ± 0.7 | 4.6 ± 0.8 |
| Glu (IU) | 17.5 ± 1.8 | 17.0 ± 2.2 | 22.8 ± 3.7a | 22.5 ± 2.7a |
| CRLB (%SD) | 6.7 ± 2.6 | 6.1 ± 1.2 | 6.4 ± 1.8 | 6.4 ± 1.3 |
| Cr (IU) | 17.4 ± 1.4 | 16.8 ± 1.5 | 16.4 ± 1.7a | 16.1 ± 1.8a |
| CRLB (%SD) | 1.9 ± 0.5 | 2.0 ± 0.4 | 1.9 ± 0.4 | 2.0 ± 0.4 |
| Cho (IU) | 4.5 ± 0.7 | 4.3 ± 0.5 | 4.0 ± 0.7a | 3.9 ± 0.6a |
| CRLB (%SD) | 2.0 ± 0.5 | 2.0 ± 0.4 | 2.1 ± 0.5 | 2.1 ± 0.5 |
| mI (IU) | 11.8 ± 2.7 | 12.4 ± 1.7 | 12.6 ± 2.6 | 12.8 ± 2.0 |
| CRLB (%SD) | 7.3 ± 3.3 | 6.1 ± 2.1 | 6.8 ± 2.2 | 6.4 ± 1.8 |
| NAA/Cr | 1.22 ± 0.13 | 1.22 ± 0.13 | 1.46 ± 0.13a | 1.46 ± 0.10a |
| Glu/Cr | 1.01 ± 0.13 | 1.01 ± 0.15 | 1.39 ± 0.20a | 1.41 ± 0.14a |
| Cho/Cr | 0.26 ± 0.03 | 0.25 ± 0.02 | 0.25 ± 0.03b | 0.24 ± 0.03b |
| mI/Cr | 0.68 ± 0.14 | 0.74 ± 0.11 | 0.77 ± 0.15b | 0.80 ± 0.15bc |
For gray matter, white matter, or CSF there were no significant within-sample differences between Time 2 and Time 1 means or between-sample differences between Smoking and Nonsmoking means on repeated-measures linear mixed-model (LMM) accounting for sex and age. For all metabolite levels, there were no significant within-sample differences between Time 2 and Time 1 on LMM accounting for sex and age. Statistically significant values are in bold (p < 0.01 on LMM). ap < 0.001, bp < 0.005 main effect of Smoking vs. non-smoking covarying age. cp < 0.05 main effect of time.
dACC dorsal anterior cingulate cortex. Time 1 after overnight abstinence. Time 2 25–55 min after the first cigarette of the morning (or corresponding times for Nonsmoking sample). NAA N-acetyl compounds. Glu glutamate. Cr creatine + phosphocreatine. Cho choline-compounds. mI myo-inositol. IU Institutional Units. CRLB Cramér-Rao lower bounds. %SD percent standard deviation.