Characteristics for Quality of Life during the Clinical Course of Interstitial Lung Disease

Abstract

Objective: Temporary improvement in health status after available therapy or medication has been reported for interstitial lung disease. However, interstitial lung disease is progressive, and there is no study on the change in quality of life over time. Therefore, we examined the time course of the Chronic obstructive pulmonary disease Assessment Test (CAT) score in relation with pulmonary function and exercise capacity.Methods: Out of 162 subjects with interstitial lung disease, 56 subjects evaluated more than twice by the CAT were assigned retrospectively to the study and divided into two groups according to the duration from disease onset. The percent of predicted forced vital capacity and diffusion capacity of the lung for carbon monoxide, and 6-min walk distance were also collected from the hospital records for analysis.Results: The CAT score improved in 21 subjects with less than five years of disease (15 to 7, p=0.004), but declined in 35 subjects with five or more years (12 to 17, p=0.002). The intervals of evaluation were not different between the groups (21 and 20 months on average, p=0.80). Forced vital capacity and diffusion capacity of the lung for carbon monoxide at baseline were more impaired in the subjects with longer disease history (p=0.001 and p=0.006, respectively). The CAT score and diffusion capacity of the lung for carbon monoxide or 6-min walk distance were correlated in each group at the baseline. Pulmonary function declined on repeated evaluation even in subjects with less than five years of disease history.Conclusion: Quality of life might be improved within five years of disease regardless of deterioration in pulmonary function; however, the improvement would become difficult afterward due to progressive change in pulmonary function or exercise capacity in interstitial lung disease.