Table 2. Comparison of sMRI Morphometric Measures Between Tobacco Ever Users and Nonusersa.
| Whole brain measures | Study period | |||||||
|---|---|---|---|---|---|---|---|---|
| Wave 1 | Wave 2 | |||||||
| Nonuse, weighted mean (SE) (n = 10 117) | Tobacco ever use, weighted mean (SE) (n = 97) | Adjusted b (SE)b | P valuec | Nonuse, weighted mean (SE) (n = 6806) | Tobacco ever use, weighted mean (SE) (n = 53) | Adjusted b (SE)b | P valuec | |
| Total cortical surface area, mm2 | 188 723.0 (942.5) | 185 088.0 (2570.2) | −5014.8 (1739.8) | .004d | 189 511.0 (940.5) | 186 833.0 (3217.0) | −5377.5 (2376.9) | .02 |
| Mean cortical thickness, mm | 2.7 (0) | 2.7 (0) | 0 (0) | .48 | 2.7 (0) | 2.7 (0) | 0 (0) | .16 |
| Total cortical volume, mm3 | 594 869.0 (2423.9) | 582 577.0 (7694.5) | −174 621.0 (5857.7) | .003d | 586 304.0 (2669.8) | 573 498.0 (11 038.0) | −21 790.8 (7043.9) | .002d |
| Subcortical gray matter volume, mm3 | 59 777.0 (162.9) | 59 114.0 (600.6) | −786.8 (537.3) | .14 | 60 533.0 (207.1) | 60 441.0 (776.9) | −589.9 (695.8) | .40 |
| Cerebral white matter volume, mm3 | 418 363.0 (1790.6) | 412 615.0 (6132.0) | −8457.3 (4696.8) | .07 | 432 787.0 (1797.2) | 430 719.0 (9166.7) | −8115.7 (6661.9) | .22 |
| Intracranial volume, mm3 | 1 485 762.0 (12 664.0) | 1 458 959.0 (12 647.0) | −38 442.8 (12 057.7) | .009d | 1 515 063.0 (13 920.0) | 1 490 582.0 (15 605.0) | −42 938.1 (22 037.7) | .05 |
Abbreviation: sMRI, structural magnetic resonance imaging.
Multivariate regression analyses were performed where the dependent variables were whole-brain measures. Sampling weights were incorporated in the survey regression analytical procedures for statistical inference at the population level. The independent variable was early age initiation of tobacco use (ever use) measured at wave 1.
Adjusted by covariates, including age, sex, race and ethnicity, pubertal stage, substance ever use, parental monitoring, school environment, handedness, imaging device manufacturer, and study site. A sensitivity analysis was performed to further account for intracranial volume (eTable 4 in the Supplement). Regression coefficients measured the association of early-age tobacco initiation as changes in sMRI measures between tobacco ever users vs control (no use).
False discovery rate (FDR) testing correction was performed to prevent inflation of type I errors.
Indicates FDR less than 0.05.