Multimorbidity, comorbidity, frailty, and venous thromboembolism.

Multimorbidity, i.e., the presence of two or more long-term health conditions, is challenging for healthcare systems worldwide. A related term is comorbidity. This denotes any condition that has existed or may occur during the clinical course of a patient who has the index disease under study. Moreover, frailty is also inter-related with multimorbidity but represents a distinct clinical concept. Few studies have explored how multimorbidity and frailty are related to venous thromboembolism (VTE), though many studies have looked at how different comorbidities, especially cancer, affect the outcome of VTE. Recently, a graded association between multimorbidity and VTE has been described. Several multimorbidity disease clusters, such as cardiometabolic and psychiatric disorders, have been associated with VTE. The comorbidity burden, i.e., Charlson Comorbidity Index (CCI), has also been related to short-term mortality after VTE. VTE patients without comorbidities, i.e., CCI = 0, have less than 1% three months mortality. Frailty and CCI have been associated with postoperative risk of VTE. In this review, drivers of multimorbidity and VTE risk, disease networks, and disease trajectories will also be discussed. Further studies including multimorbidity and frailty as predictors for VTE in situations of risk could be of clinical importance. Moreover, it will also be important to determine which diseases should be included in a multimorbidity risk score for VTE.