Comorbidities in multiple myeloma and implications on survival: A population-based study.

High proportion of patients with multiple myeloma suffer from comorbidities which may alter clinical management. Therefore, our aims were to evaluate the prevalence of comorbidities and their impact on survival. We included patients diagnosed with multiple myeloma 1990-2013 in Sweden and all diagnoses from each patient from 1985. A total of 13 656 patients with multiple myeloma were included in the study, thereof 7404 (54%) had comorbidity at diagnosis. The risk of death was increased for those with one comorbidity at diagnosis compared to those without any comorbidity (hazard ratio = 1.19; 95% confidence interval:1.14-1.25); this risk was higher for those with two (1.38; 1.30-1.47) and three or more comorbidities (1.72; 1.62-1.83). Furthermore, the risk of death was increased in patients with prior history of cancer, arrhythmia, heart failure, diabetes mellitus, cerebrovascular disease, chronic lung disease, psychological disease, peptic ulcer, neurological disease, peripheral vascular disease, chronic kidney disease, dementia, and inflammatory bowel disease. This large study shows that over 50% of multiple myeloma patients have a comorbidity at diagnosis and survival decreased with increasing numbers of comorbidities. This emphasizes the importance of comorbidities when evaluating patients and deciding on treatment strategies for individuals with multiple myeloma.