Is inflammatory chronic obstructive pulmonary disease a coronary heart disease risk equivalent? A longitudinal analysis of the third National Health and Nutrition Examination Survey (NHANES III), 1988–1994

BACKGROUND: Evidence suggests that there is an association between chronic obstructive pulmonary disease (COPD) and coronary heart disease (CHD). An important etiological link between COPD and CHD may be an underlying systemic inflammatory process. Given that COPD patients are at greater risk of cardiovascular mortality, understanding the burden of CHD on COPD patients could permit future risk attenuation. METHODS: Longitudinal cohort analyses of the Third National Health and Nutrition Examination Survey from 1988–1994 were performed. 3,681 individuals ≥40 years of age with good quality spirometry data were included. Participants were divided into 5 groups: 1) no COPD, no CHD; 2) COPD without inflammation, no CHD; 3) COPD with inflammation, no CHD; 4) CHD only, and 5) CHD + COPD. A novel “inflammatory” COPD designation included those with COPD and clinical evidence of inflammation (i.e., CRP ≥95.24 nmol/L). RESULTS: The risk for CHD mortality was significant only for the CHD group (HR 5.56, 95% CI 3.24-9.55) and the COPD + CHD group (HR 5.02, 95% CI 2.83-8.90). Similarly, the risk for cardiovascular disease (CVD) mortality was significant only for the CHD group (HR 4.25, 95% CI 2.70-6.69) and the CHD + COPD group (HR 4.12, 95% CI 2.60-6.54) after adjusting for nonmodifiable CHD risk factors (age, gender, race/ethnicity, family history of CHD). After adjusting for modifiable CHD risk factors (diabetes, BMI, physical activity, systolic blood pressure, cholesterol, and smoking), hazard ratios of the two groups remained similar but attenuated. For total mortality, the risk was significant for the four groups: the non-inflammatory COPD group; the COPD with inflammation group, the CHD group, and the COPD + CHD group. CONCLUSIONS: Our study did not confirm that inflammatory COPD may be a CHD risk equivalent. However, due to the small size of the “inflammatory” COPD group, further prospective replication and validation is needed. Moreover, given that COPD results from inflammation, the systemic inflammation associated with COPD may have worsened comorbid conditions and may have lead to the increased total mortality found in the COPD with inflammation and COPD + CHD groups which requires further investigation.