Comorbidity among patients with colon cancer in New Zealand.

Aims: To identify patient factors that are associated with a higher risk of comorbidity, and to assess the impact of comorbidity on risk of in-hospital death, length of stay and 5-year all-cause survival among a large cohort of patients with colon cancer in New Zealand.

Methods: Comorbidity data were collected from patients who were diagnosed with colon cancer and admitted to public hospitals during 1996-2003. The comorbidity measures included all conditions listed in the Charlson Comorbidity Index, as well as a predetermined list of additional conditions. We examined predictors of higher comorbidity scores. We also measured the impact of comorbidity on in-hospital death, length of stay and 5-year all-cause survival using logistic, linear and Cox proportional hazard regression models to adjust for confounding by sex, age, ethnicity, extent of disease and area level deprivation.

Results: There were 11,524 patients included in the study. 7.5% of females and 10.3% of men had Charlson scores of three or more. Higher comorbidity scores were associated with increasing age, and were more common among males, Māori and Pacific people, those with unknown extent of disease and those living in the most deprived quintile of New Zealand. Those with Charlson scores ≥ 3 had a higher risk of in-hospital death (OR=4.8; 95% CI 3.5-6.6), longer lengths of hospital stay (0.14 days 95% CI 0.08-0.2) and lower 5-year survival HR=2.0; 95%CI=1.8-2.3) compared with those with a score of 0.

Conclusion: This study confirms that comorbidity is common among colon cancer patients in New Zealand, and has an adverse and independent effect on outcomes related to mortality and length of hospital stay.