Impact of chronic obstructive pulmonary disease on mortality: A large national cohort study

Abstract

Background and objective The global burden of chronic obstructive pulmonary disease (COPD) is increasing and COPD patients are at higher risk for all-cause mortality. We aimed to evaluate the impact of COPD on specific-cause mortality using national data.

Methods This was nationwide retrospective cohort study of 340, 767 adults aged 40-84 years who lacked COPD diagnosis at baseline between 1 January 2003 and 31 December 2013. Incident COPD was defined by reference to COPD claim codes and prescription of COPD medication at least twice annually. Cox proportional hazard ratio (HR) for each cause of death in the COPD group was compared to that of the non-COPD group, with other causes of death accounted as the competing risk.

Results All-cause mortality was higher in the COPD (2,978 per 100, 000 person-years) than the non-COPD group (629 per 100, 000 person-years) and adjusted HR was 1.41 (95% CI = 1.32, 1.50). The association was particularly strong for chronic lower airway disease (adjusted sub-HR = 9.67; 95% CI = 7.21, 12.96) and lung cancer (adjusted sub-HR = 3.16; 95% CI = 2.68, 3.71), and the association was stronger in those aged <60 years.

Conclusion In this large national cohort, COPD patients were at a statistically significant higher risk for all-cause mortality than those without COPD. They were more likely to die from chronic lower airway disease, lung cancer and pneumonia than subjects without COPD. The impact of COPD on specific mortalities was stronger in younger subjects.