Impact of heart failure and other comorbidities on mortality in patients with chronic obstructive pulmonary disease: a register-based, prospective cohort study

BACKGROUND: Multimorbidity has already become common in primary care and will be a challenge in the future. Primary care in Sweden participates to a great extent in the care of patients with two severe, chronic conditions: chronic obstructive pulmonary disease (COPD) and heart failure. Both conditions are characterized by high mortality and often coexist. Age, sex, heart failure and other comorbidities are considered to be the major predictors of mortality in patients with COPD. We aimed to study the impact of heart failure, other comorbidities, age and sex on mortality in patients with COPD. METHODS: A register-based, prospective cohort study conducted in Blekinge County in Sweden with about 150,000 inhabitants. The study population was comprised of people aged ≥35 years. The data about diagnoses of COPD and heart failure came from the 2007 health care register, in which we found 984 individuals with a diagnosis of COPD. Date of death was collected from January 1st, 2008 –August 31st, 2015. The diagnosis-based Adjusted Clinical Groups (ACG) Case-Mix System 7.1 was used to describe comorbidity. Each individual was assigned one of six comorbidity levels called resource utilization bands (RUB) graded from 0 to 5. RESULTS: Estimated eight year mortality in patients with COPD and coexisting heart failure was seven times higher than in patients with COPD alone - odds ratio 7.06 (95% CI 3.88–12.84). Adjusting for age and male sex resulted in odds ratio 3.75 (95% CI 1.97–7.15). Further adjusting for other comorbidities resulted in odds ratio 3.26 (95% CI 1.70–6.25). The mortality was strongly associated with the highest comorbidity level – RUB 5 where the odds ratio was 5.19 (95% CI 2.59–10.38). CONCLUSION: Heart failure has an important impact on mortality in patients with COPD. The mortality in patients with COPD and coexisting heart failure was strongly associated with age, male sex and other comorbidities. Of those three predictors, only other comorbidities can be influenced. Heart failure and other comorbidities should be recognized early and properly treated in order to improve survival in patients with coexisting COPD and heart failure.