Introduction
Projections on healthcare impact of chronic obstructive pulmonary disease (COPD) over the next 15 years indicate a rapidly escalating health and societal burden mainly due to population ageing and comorbidities.1 2 It is well-known that highly prevalent chronic conditions such as cardiovascular disorders, type 2 diabetes mellitus—metabolic syndrome and/or anxiety–depression often occur as comorbid conditions in patients with COPD.3
Whereas the current standards on COPD management4 acknowledge the adverse effects of comorbidities on COPD prognosis, they suggest that ‘presence of comorbidities should not alter COPD treatment, and comorbidities should be treated per usual standards regardless of the presence of COPD’. However, recent evidence prompts the need for novel approaches in the prevention and management of comorbidities in patients with COPD to effectively reduce the overall burden of the disease.5 6
Identification of such cost-effective strategies aiming at preventing and enhancing management of comorbid conditions in patients with COPD requires deeper knowledge on epidemiological patterns and shared biological pathways explaining co-occurrence of diseases.7 Recently, Gomez-Cabrero et al 8 reported the higher risk of developing certain comorbidities in patients with COPD, as compared with patients without COPD. The study used a data-driven analysis of Medicare registries from 13 million hospitalised patients over 65 years. The authors also proposed underlying biological mechanisms that may explain the identified comorbidities. Another direction of comorbidity research aims to uncover temporal disease co-occurrence patterns, showing great potential to explain the dynamics of disease co-occurrence and to highlight characteristic disease sequences potentially caused by underlying mechanisms and common risk factors. As an example, a recent study identified COPD as a central disease with rapid progression to many other conditions, stressing the importance of its early diagnosis.9
In order to gain deeper knowledge on epidemiological patterns explaining co-occurrence of diseases,7 the primary aim of the current study is to reinforce previous evidence on the higher risk of comorbidities in patients with COPD.8 To this end, we conducted a similar analysis to the recent work by Gomez-Cabrero et al 8 on an independent dataset retrieved from the Catalan Healthcare Surveillance System (CHSS) in Spain,10 which accounts for 1.4 million patients over 65 years with chronic conditions recruited across all healthcare tiers. The research also explored the temporal order of disease diagnosis of COPD and comorbidities at a population level which might help to further understand the dynamics of comorbidity clustering often seen in patients with COPD.3 11