Trajectories were identified using LCGA (Muthén & Muthén, 2000; Nagin, 1999). Linear trajectory models specifying two through six classes were tested. Several recommended criteria were used to determine which model to retain (Nagin, 1999, 2005). Participants were then assigned to their trajectory group based on posterior probabilities for each class. Chi-square analyses were conducted to compare different trajectory groups on a number of discrete descriptive smoking characteristics and disease outcome variables. Where a significant result was found, post-hoc paired comparisons were conducted. Finally, a discrete time survival LCGA was conducted to evaluate whether progression in the probability of mortality (mortality hazard rate) varied across trajectory classes.
