title: Does comorbidity interact with colorectal cancer to increase mortality? A nationwide population-based cohort study.
abstract: BACKGROUND
  It is unknown whether comorbidity interacts with colorectal cancer (CRC) to increase the rate of mortality beyond that explained by the independent effects of CRC and comorbid conditions.
  
  
  METHODS
  We conducted a cohort study (1995-2010) of all Danish CRC patients (n=56963), and five times as many persons from the general population (n=271670) matched by age, gender, and specific comorbidities. To analyse comorbidity, we used the Charlson Comorbidity Index (CCI) scores. We estimated standardised mortality rates per 1000 person-years, and calculated interaction contrasts as a measure of the excess mortality rate not explained by the independent effects of CRC or comorbidities.
  
  
  RESULTS
  Among CRC patients with a CCI score=1, the 0-1 year mortality rate was 415 out of 1000 person-years (95% confidence interval (CI): 401, 430) and the interaction accounted for 9.3% of this rate (interaction contrast=39 out of 1000 person-years, 95% CI: 22, 55). For patients with a CCI score of 4 or more, the interaction accounted for 34% of the mortality (interaction contrast=262 out of 1000 person-years, 95% CI: 215, 310). The interaction between CRC and comorbidities had limited influence on mortality beyond 1 year after diagnosis.
  
  
  CONCLUSIONS
  Successful treatment of the comorbidity is pivotal and may reduce the mortality attributable to comorbidity itself, and also the mortality attributable to the interaction.
authors.affiliation: Department of Clinical Epidemiology, Aarhus University Hospital, Olof Palmes Alle 43-45, 8200 Aarhus N, Denmark.
authors.forename: R
authors.initials: R
authors.lastname: Erichsen
authors.forename: E
authors.initials: E
authors.lastname: Horváth-Puhó
authors.forename: L H
authors.initials: LH
authors.lastname: Iversen
authors.forename: T L
authors.initials: TL
authors.lastname: Lash
authors.forename: H T
authors.initials: HT
authors.lastname: Sørensen
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015331:Cohort Studies; D015179:Colorectal Neoplasms / Q000453:epidemiology* / Q000401:mortality*; D015897:Comorbidity; D003718:Denmark; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D012042:Registries; D015996:Survival Rate
references.citation: Inflamm Bowel Dis. 2013 Mar-Apr;19(4):800-5
references.pmid: 23435402
references.citation: J Gerontol A Biol Sci Med Sci. 2010 Mar;65(3):322-9
references.pmid: 20018824
references.citation: BMC Cancer. 2009 Apr 20;9:116
references.pmid: 19379520
references.citation: J Gastrointest Surg. 2004 Dec;8(8):1061-7
references.pmid: 15585394
references.citation: Dis Colon Rectum. 2009 Jan;52(1):71-8
references.pmid: 19273959
references.citation: J Am Geriatr Soc. 2006 Dec;54(12):1898-904
references.pmid: 17198496
references.citation: Scand J Public Health. 2011 Jul;39(7 Suppl):42-5
references.pmid: 21775350
references.citation: Ann Oncol. 2011 Jan;22(1):118-126
references.pmid: 20603436
references.citation: J Clin Oncol. 2004 Aug 1;22(15):3099-103
references.pmid: 15284260
references.citation: Br J Cancer. 2008 Jan 15;98(1):60-70
references.pmid: 18059401
references.citation: World J Surg. 2007 Jan;31(1):192-9
references.pmid: 17180570
references.citation: Scand J Public Health. 2011 Jul;39(7 Suppl):22-5
references.pmid: 21775345
references.citation: Ann Surg. 2011 Nov;254(5):738-43; discussion 743-4
references.pmid: 21997816
references.citation: Cancer. 1998 Jun 1;82(11):2123-34
references.pmid: 9610691
references.citation: Br J Surg. 2005 May;92(5):615-23
references.pmid: 15779071
references.citation: Dan Med Bull. 1999 Jun;46(3):263-8
references.pmid: 10421985
references.citation: Dan Med Bull. 1997 Nov;44(5):535-9
references.pmid: 9408738
references.citation: Eur J Cancer. 2007 Oct;43(15):2179-93
references.pmid: 17681780
references.citation: Br J Gen Pract. 2006 Nov;56(532):863-8
references.pmid: 17132354
references.citation: BMC Med Res Methodol. 2011 May 28;11:83
references.pmid: 21619668
references.citation: Br J Cancer. 2012 Mar 27;106(7):1353-60
references.pmid: 22353805
references.citation: Int J Colorectal Dis. 2009 Sep;24(9):1097-109
references.pmid: 19495779
references.citation: Int J Cancer. 2010 Dec 15;127(12):2893-917
references.pmid: 21351269
references.citation: Eur J Cancer. 2000 Jan;36(1):95-9
references.pmid: 10741301
references.citation: Crit Rev Oncol Hematol. 2005 Sep;55(3):231-40
references.pmid: 15979890
references.citation: Langenbecks Arch Surg. 2002 Jun;387(2):72-6
references.pmid: 12111258
references.citation: Ann Intern Med. 2006 Nov 7;145(9):646-53
references.pmid: 17088577
references.citation: N Z Med J. 2011 Jul 08;124(1338):76-88
references.pmid: 21946965
references.citation: Science. 2000 Mar 31;287(5462):2398-9
references.pmid: 10766613