Abstract

The aim of this study was to establish which cut-off point for the forced expiratory volume in 1 s (FEV1)/forced vital capacity (FVC) ratio (i.e. fixed 0.70 or lower limit of normal (LLN) cut-off point) best predicts accelerated lung function decline and exacerbations in middle-aged smokers.

We performed secondary analyses on the Lung Health Study dataset. 4045 smokers aged 35–60 years with mild-to-moderate obstructive pulmonary disease were subdivided into categories based on presence or absence of obstruction according to both FEV1/FVC cut-off points. Post-bronchodilator FEV1 decline served as the primary outcome to compare subjects between the categories.

583 (14.4%) subjects were nonobstructed and 3230 (79.8%) subjects were obstructed according to both FEV1/FVC cut-off points. 173 (4.3%) subjects were obstructed according to the fixed cut-off point, but not according to the LLN cut-off point (‘‘discordant’’ subjects). Mean¡SE post-bronchodilator FEV1 decline was 41.8¡2.0 mL?year-1 in nonobstructed subjects, 43.8¡3.8 mL?year-1 in discordant subjects and
53.5¡0.9 mL?year-1 in obstructed subjects (p,0.001).

Our study showed that FEV1 decline in subjects deemed obstructed according to a fixed criterion (FEV1/FVC ,0.70), but non-obstructed by a sex- and age-specific criterion (LLN) closely resembles FEV1 decline in subjects designated as non-obstructed by both criteria. Sex and age should be taken into account when assessing airflow obstruction in middle-aged smokers.
European Respiratory Journal 2014 43: 54-63; DOI: 10.1183/09031936.00158212

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