Association of Gas Diffusing Capacity of the Lung for Carbon Monoxide with Cardiovascular Morbidity and Survival in a Disadvantaged Clinical Population

Abstract

Low diffusing capacity of the lung for carbon monoxide (DLCO) and spirometry values are associated with increased mortality risk. However, associations between mortality risk and cardiovascular disease with the transfer coefficient of the lung for carbon monoxide (KCO) and alveolar volume (VA) are unknown. This cohort study: (i) evaluated whether DLCO, KCO, and VA abnormalities are independently associated with cardiovascular morbidity and/or elevated mortality risk and, (ii) compared these associations with those using spirometry values. Gas-diffusing capacity and spirometry data of 1165 adults seen at specialist respiratory outreach clinics over an 8-year period (241 with cardiovascular disease; 108 deceased) were analysed using multivariable Cox and logistic regression. DLCO, KCO, and VA values below the lower limit of normal (< - 1.64 Z-scores) were associated with elevated cardiovascular disease prevalence [respective odds ratios of 1.83 (95% CI 1.31-2.55), 1.56 (95% CI 1.08-2.25), 2.20 (95% CI 1.60-3.01)] and increased all-cause mortality risk [respective hazard ratios of 2.99 (95% CI 1.83-4.90), 2.14 (95% CI 1.38-3.32), 2.75 (95% CI 1.18-2.58)], after adjustment for factors including age, personal smoking, and respiratory disease. Compared to similar levels of spirometry abnormality, DLCO, KCO, and VA were associated with similar or greater mortality risk, and similar cardiovascular disease prevalence. Analysis of only those patients with clinical normal spirometry values (n = 544) showed these associations persisted for DLCO. Low DLCO, KCO, and VA measurements are associated with cardiovascular disease prevalence. As risk factors of all-cause mortality, they are more sensitive than spirometry even among patients with no diagnosed respiratory disease.