FIGURE 2.

Adjusted brain age gap (BAG) and its relationships with smoking status in the testing set. (a) The relationship between the adjusted predicted brain age $({\widehat{Y}}_{\text{adj}})$ and chronological age in different smoking statuses (SS) (R = coefficients of correlation; MAE = mean absolute error). (b) The distribution of adjusted BAG $\left(\mathrm{\Delta }{G}_{adj})\right.$ between different SS groups in separate chronological age categories, where P indicates the P-value corresponding to the comparison between nonsmokers (non-SMK) and smokers (SMK) in each category. (c) The effect size with the 95% confidence interval for testing the difference between non-SMK and SMK within each age category based on (b). (d) The number of participants in each age group corresponding to comparisons between non-SMK and SMK in (b)