The Association of Lung Clearance Index with COPD and FEV1 Reduction in ‘Men Born in 1914’

Lung Clearance Index (LCI) provides an overall measurement of ventilation inhomogeneity. This population-based study examines whether LCI predicts pulmonary obstruction and incidence of chronic obstructive pulmonary disease (COPD) events over a long-term follow-up. Multiple breath nitrogen washout and spirometry were performed in 674 men from the cohort “Men born in 1914” at age 55 years. Subjects were classified into quartiles (Q) of LCI and according to LCI above and below upper limit of normal (ULN). Incidence of COPD events (COPD hospitalisations or COPD-related deaths) were monitored over the remaining life span of the men, by linkage with national hospital registers. In addition, development of pulmonary obstruction (i.e., FEV¹/vital capacity below lower limit of normal (LLN)) was studied in 387 men who were re-examined with spirometry at 68 years of age. Over 44 years of follow-up, there were 85 incident COPD events. Hazards ratios (HRs) for COPD across quartiles of LCI were: Q1 1.00 (reference), Q2 1.30 (95% confidence interval: 0.61–2.74), Q3 1.97 (0.97–3.98) and Q4 3.99 (2.06–7.71) (p value for trend <0.001). This relationship remained significant after adjustments for confounding factors, including smoking and FEV¹ (HR, Q4 vs Q1: 2.34 (1.17–4.69); p value for trend: 0.006). Reduction of FEV¹ between 55 and 68 years of age and incidence of pulmonary obstruction was highest in those with high LCI. High LCI is associated with future development of pulmonary obstruction and incidence of COPD hospitalisations in men from the general population.