To our knowledge, 2 studies have investigated the association between multimorbidity and dementia risk.10,11 Both found that multimorbidity was associated with an increased risk of dementia, while one found that neuropsychiatric, cardiovascular, and sensory impairment or cancer clusters, but not a respiratory, metabolic, and musculoskeletal cluster, were associated with an increased risk.11 The same study found no evidence that apolipoprotein (APOE) ε4, the strongest genetic risk factor for dementia,12 modified these associations.11 Here, APOE is linked to cancer.