BACKGROUND Impaired lung function is associated with a higher risk of developing lung cancer. However, lung function is a dynamic variable and must be evaluated longitudinally. This study reports on the relationship between accelerated lung function decline and development of lung cancer.

RESEARCH QUESTION Is accelerated lung function decline associated with the development of lung cancer?

STUDY DESIGN AND METHODS A longitudinal, observational study was performed by using epidemiologic data from two population-based studies comprising subjects assessed biannually from 2001 to 2019 in South Korea. Eligible subjects were between 40 and 69 years of age and were followed up by using spirometry. Spirometry measurements were made at each follow-up. Patients with a decline in FEV₁ > 60 mL per year were defined as rapid FEV₁ decliners. The relationship between lung cancer and rapid FEV₁ decline was evaluated by using adjusted Cox regression models with covariates, including age, sex, smoking history, FEV₁/FVC, and WBC count.

RESULTS Among the 8,549 eligible subjects, 1,287 (15.1%) had rapid FEV₁ decline, and 48 (0.6%) had newly developed lung cancer. The risk of lung cancer development was increased in the subjects aged ≥ 45 years and those with ≥ 30 pack-years of smoking, low baseline FEV₁/FVC, low forced expiratory flow between 25% and 75% of vital capacity, rapid FEV₁ decline, and increased WBC count. Rapid FEV₁ decline was an independent risk factor for lung cancer development (adjusted hazard ratio, 2.34; 95% CI, 1.28-4.28; P = .006). Time-dependent net reclassification improvement showed a benefit of FEV₁ decline rate in determining subjects at risk of lung cancer when added to conventional practice (categorical, 0.32 [95% CI, 0.00-0.64]; continuous, 0.83 [95% CI, 0.14-1.25]).

INTERPRETATION The FEV₁ decline rate may be a potential biomarker for lung cancer development. Further study is needed to identify whether patients with rapid FEV₁ decline warrant lung cancer assessment or screening.