Disentangling Positive Affect Heterogeneity in a Digital Physical Activity Intervention for Young Adult Cancer Survivors: A Group‐Based Multi‐Trajectory Modeling Approach

ABSTRACT Background As research on behavioral interventions for young adult cancer survivors (YACS) progresses, understanding heterogeneity in positive affect experienced with health behaviors is essential to enhancing intervention effectiveness and improving survivorship outcomes. Methods Group‐based multi‐trajectory modeling was conducted on data from the 6‐month intervention phase of the IMproving Physical Activity after Cancer Treatment (IMPACT) study to uncover trajectories of positive affect related to physical activity (PA) (PA enjoyment, mood after PA) among intervention participants (n = 140). Differences in baseline predictors were assessed using ANOVA and χ 2, and moderate‐to‐vigorous physical activity (MVPA) measures were analyzed using multi‐level linear mixed models. Results Three trajectories were identified: Low‐Affect (n = 57), Mid‐Affect (n = 58), and High‐Affect (n = 22). Participants in Mid‐Affect and High‐Affect reported higher levels of being partnered and incomes > 60, 000, while those in Low‐Affect reported worse baseline psychosocial and health‐related quality of life factors (p 0. 05). Conclusions These findings highlight variation in positive affect trajectories, their baseline predictors, and how they relate to MVPA goal adherence. Interventions that foster positive affect related to PA and offer support based on positive affect trajectory may improve MVPA and survivorship outcomes for YACS. Clinical Trial Registration ClinicalTrials. gov ID: NCT03569605, https: //clinicaltrials. gov/study/NCT03569605.