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

Purpose: Low diffusing capacity of the lung for carbon monoxide (D_LCO) 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 (K_CO) and alveolar volume (V_A) are unknown. This cohort study: (i) evaluated whether D_LCO, K_CO, and V_A abnormalities are independently associated with cardiovascular morbidity and/or elevated mortality risk and, (ii) compared these associations with those using spirometry values. Methods: 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. Results: D_LCO, K_CO, and V_A 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, D_LCO, K_CO, and V_A 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 D_LCO. Conclusion: Low D_LCO, K_CO, and V_A 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.