title: Does comorbidity interact with prostate cancer to increase mortality? A Danish cohort study of 45 326 prostate cancer patients diagnosed during 1995-2011.
abstract: BACKGROUND
  Many prostate cancer patients die of other causes, but it remains unknown whether comorbidity interacts synergistically with prostate cancer to increase the mortality rate beyond that explained by the individual risks of comorbidity and prostate cancer.
  
  
  METHODS
  A nationwide cohort study of 45 326 Danish prostate cancer patients diagnosed during 1995-2011, each matched to approximately five men from the general population on age and individual comorbidities in the Charlson Comorbidity Index (CCI). We calculated five-year mortality rates and interaction contrasts as a measure of the excess mortality rate explained by synergy between prostate cancer and comorbidity.
  
  
  RESULTS
  Five-year mortality was 46.8% in prostate cancer patients and 25.8% in matched men from the general population. For prostate cancer patients with a CCI score of 2-3, the mortality rate was 250 per 1000 person-years [95% confidence interval (CI): 236, 263], and interaction between comorbidity and prostate cancer accounted for 20% of the total mortality rate (50 deaths per 1000 person-years, 95% CI 35, 65) in the first year following cancer diagnosis. The interaction was mainly present for patients with metastatic disease and those not treated with prostatectomy.
  
  
  CONCLUSIONS
  Up to 20% of all deaths among men who had both prostate cancer and comorbidities could be explained by the comorbidity-prostate cancer interaction. The mortality attributable to comorbidity itself and the mortality attributable to the interaction may be reduced by successful treatment of the comorbidity.
authors.affiliation: a Department of Clinical Epidemiology , Aarhus University Hospital , Aarhus , Denmark ;
authors.forename: Anne Gulbech
authors.initials: AG
authors.lastname: Ording
authors.affiliation: a Department of Clinical Epidemiology , Aarhus University Hospital , Aarhus , Denmark ;
authors.forename: Erzsébet
authors.initials: E
authors.lastname: Horváth-Puhó
authors.affiliation: a Department of Clinical Epidemiology , Aarhus University Hospital , Aarhus , Denmark ;|b Department of Epidemiology , Rollins School of Public Health, Emory University , Atlanta , Georgia , USA ;
authors.forename: Timothy L
authors.initials: TL
authors.lastname: Lash
authors.affiliation: a Department of Clinical Epidemiology , Aarhus University Hospital , Aarhus , Denmark ;
authors.forename: Vera
authors.initials: V
authors.lastname: Ehrenstein
authors.affiliation: c Department of Urology , Aarhus University Hospital , Aarhus , Denmark ;
authors.forename: Michael
authors.initials: M
authors.lastname: Borre
authors.affiliation: d Institute of Pathology, Aalborg University Hospital , Aalborg , Denmark.
authors.forename: Mogens
authors.initials: M
authors.lastname: Vyberg
authors.affiliation: a Department of Clinical Epidemiology , Aarhus University Hospital , Aarhus , Denmark ;
authors.forename: Henrik Toft
authors.initials: HT
authors.lastname: Sørensen
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015331:Cohort Studies; D015897:Comorbidity; D003718:Denmark / Q000453:epidemiology; D006801:Humans; D015994:Incidence; D008297:Male; D011471:Prostatic Neoplasms / Q000401:mortality*; D018570:Risk Assessment; D016019:Survival Analysis