Why are patients with chronic obstructive pulmonary disease at increased risk of cardiovascular diseases? The potential role of systemic inflammation in chronic obstructive pulmonary disease

Abstract

Background: Chronic obstructive pulmonary disease (COPD) increases the risk of cardiovascular disease 2- to 3-fold. The factors responsible for this association remain largely unknown.

Methods and results: We analyzed data from participants, > or =50 years of age, of the Third National Health and Nutrition Examination Survey (n=6629) to determine whether C-reactive protein (CRP) and other systemic inflammatory markers are present in participants with chronic airflow obstruction and are associated with cardiac injury. Participants with severe airflow obstruction had circulating leukocyte, platelet, and fibrinogen levels that were 460/ microL (95% confidence interval [CI], 30 to 890/ microL), 39 510/ microL (95% CI, 21 730 to 57 290/ microL), and 41.63 mg/dL (95% CI, 19.87 to 63.39 mg/dL) higher, respectively, than in those without airflow obstruction. They were also 2.18 times (95% CI, 1.46 to 3.27) more likely to have an elevated circulating CRP level. Moderate airflow obstruction was associated with smaller but still significant increases in these levels. Moderate and severe airflow obstruction was associated with increased occurrence of ischemic changes on electrocardiograms of participants. In the presence of both highly elevated CRP and moderate or severe airflow obstruction, the Cardiac Infarction Injury Score was 2.68 and 5.88 U higher, respectively, than in those without airflow obstruction and with low CRP, which suggests an additive effect of CRP and COPD on the risk of cardiac injury.

Conclusion: Low-grade systemic inflammation was present in participants with moderate to severe airflow obstruction and was associated with increased risk of cardiac injury. This may in part explain the high rates of cardiovascular complications in COPD.