Figure 4
Associations between the number of years since last smoked and local cortical thickness (n=259). Areas in orange–yellow shades represent statistically significant associations at a false discovery rate (FDR)=0.05. Color bar represents FDR q-values. For a description of what three-dimensional (3D) perspective each specific brain image represents, see Figure 2 legend. (a) Association between the number of years since last smoked and cortical thickness controlling for pack-years, gender and exact age at scanning. A scatterplot of the association between pack-years and mean cortical thickness within significant areas of recovery is also provided (thickness values in mm). (b) For visualization purposes, a bar graph depicting centered mean cortical thickness within areas of recovery in a sub-sample of early quitters (⩾28 years since quitting), late quitters (<28 years since quitting) and current smokers precisely matched for pack-years. The mean pack-years for each of the three groups is 24.4 pack-years. The mean reported number of cigarettes smoked per day was 8.9 for current smokers against 16.1 for late quitters and 31.7 cigarettes for early quitters. The complete subsample of those that never smoked was used in order to get the best possible estimate of mean thickness for that group, as it was not constrained by the requirements of matching for pack-years.
