Investigation of time profile of FEV1 across the onset of COPD: A retrospective cohort study using medical checkup data in Japan

Abstract

Abstract Background: Identification of the factors associated with a rapid decline in forced expiratory volume in 1 second (FEV1) at an early stage of chronic obstructive pulmonary disease (COPD) is of particular clinical importance because it may allow timely medical intervention to slow down progression of lung function decline in patients. This study aimed to compare the time profile of FEV1 after COPD diagnosis among rapid decliners, slow decliners, and sustainers and the patient characteristics in the year of COPD diagnosis.Methods: COPD patients were identified from data collected from the annual medical checkup records of Hitachi, Ltd. employees in Japan from April 1998 to March 2019. Patients were categorized by FEV1 for 5 years (years 1-5) in 3 groups (rapid decliner, slow decliner, and sustainer). Patients with a decrease of FEV1 ≥63 mL/year were considered rapid decliners; those with <63 and ≥31 mL/year, slow decliners; and those with <31 mL/year, sustainers. Patient characteristics in the year of COPD detection and the time profiles of FEV1 across the onset of COPD (from year ‑3 to 5) were investigated in those groups.Results: Of 1294 eligible participants, 241 (18.6%) were classified as rapid decliners. The annual rates of FEV1 decline were similar 3 years before and until COPD diagnosis (year -3 to 0) and were 0.05 mL in rapid decliners, 0.05 mL in slow decliners, and 0.07 mL in sustainers. After COPD diagnosis, these 3 categories started diverging in their lung function trajectory. The mean FEV1 in rapid decliners was 2.82 L in year 0 and 2.41 L in year 5. Rapid decliners had decreased body mass index, waist circumference, and body fat percentage at the time of COPD diagnosis compared with sustainers.Conclusions: FEV1 declined yearly before diagnosis in rapid decliners, slow decliners, and sustainers. The time profiles of FEV1 were different in the 3 groups after COPD diagnosis. Therefore, regular lung function tests are necessary to follow FEV1 decline after COPD onset in a timely manner.