Grant Williams

Background Multimorbidity is associated with premature mortality and excess health care costs. The burden of multimorbidity is highest among patients with cancer, yet trends and determinants of multimorbidity over time are poorly understood. Methods Via Medicare claims linked to Cancer Prevention Study II data, group‐based trajectory modeling was used to compare National Cancer Institute comorbidity index score trends for cancer survivors and older adults without a cancer history. Among cancer survivors, multinomial logistic regression analyses evaluated associations between demographics, health behaviors, and comorbidity trajectories. Results In 82,754 participants (mean age, 71.6 years [SD, 5.1 years]; 56.9% female), cancer survivors ( n = 11,265) were more likely than older adults without a cancer history to experience the riskiest comorbidity trajectories: (1) steady, high comorbidity scores ( remain high ; odds ratio [OR], 1.36; 95% CI, 1.29–1.45), and (2) high scores that increased over time ( start high and increase ; OR, 1.51; 95% CI, 1.38–1.65). Cancer survivors who were physically active postdiagnosis were less likely to fall into these two trajectories (OR, 0.73; 95% CI, 0.64–0.84, remain high ; OR, 0.42; 95% CI, 0.33–0.53, start high and increase ) compared to inactive survivors. Cancer survivors with obesity were more likely to have a trajectory that started high and increased (OR, 2.83; 95% CI, 2.32–3.45 vs. normal weight), although being physically active offset some obesity‐related risk. Cancer survivors who smoked postdiagnosis were also six times more likely to have trajectories that started high and increased (OR, 6.86; 95% CI, 4.41–10.66 vs. never smokers). Conclusions Older cancer survivors are more likely to have multiple comorbidities accumulated at a faster pace than older adults without a history of cancer. Weight management, physical activity, and smoking avoidance postdiagnosis may attenuate that trend.