LAUSR

To investigate if comorbidity predicts mortality and functional impairment in middle-aged individuals with cancer (50–64 years) as compared to older individuals. A prospective cohort study. Outcomes were mortality and functional impairment at 5 years follow-up. Comorbidity was assessed using adjusted Charlson comorbidity index and polypharmacy (≥ 5 drugs) as surrogate for comorbidity. Multivariate Cox-proportional hazards and binary logit models were used to assess the risk of 5-year mortality and functional impairment respectively. We included 477 middle-aged (50–64 years) and 563 older (65 + years) individuals with cancer. The prevalence of comorbidity (at least one disease in addition to cancer) was 29% for middle-aged and 45% for older individuals, with polypharmacy observed in 15% and 31% respectively. Presence of ≥ 3 comorbidities was associated with nearly three times as high a risk of mortality in middle-aged individuals (HR 2.97, 95% CI: 1.43–6.16). In older individuals, the HR was 1.7 (95% CI 1.1–2.8). Polypharmacy was associated with a higher risk of mortality in middle-aged (HR 2.35, 95% CI 1.32–4.16) but not in older individuals (HR 1.2, 95% CI 0.9–1.8). Polypharmacy was associated with the four time the risk of functional impairment in middle-aged (OR 4.0, 95% CI 1.59–10.06) and older individuals (OR 4.4, 95% CI 1.6–11.7). This study of middle-aged and older adults with cancer shows that comorbid disease is common in younger and older individuals with cancer and are associated with inferior outcomes. Assessment and management of comorbidity should be a priority for cancer care across all age groups.