Yoojin Nam, Hye Ree Cho, Eunji Kim, Nak Gyeong Ko, Pa Hong, Hyun Kyu Cho
Among ever-smokers, incidental emphysema on screening chest CT is associated with mortality after adjustment for pack-years, although residual smoking-intensity confounding cannot be excluded. Once smoking history is known, the report adds almost nothing to discrimination and should not be used alone to stratify prognosis; whether it should prompt evaluation for undiagnosed COPD we did not address. In the full screening population the association did not reach significance, but with 284 deaths, half the number needed for 80% power, that result is inconclusive rather than negative.
BACKGROUND: Incidental emphysema on health-screening chest CT is common, yet its prognostic significance in asymptomatic populations is poorly characterized.
RESEARCH QUESTION: Is incidental emphysema on health screening chest CT independently associated with all-cause mortality?
STUDY DESIGN AND METHODS: This retrospective cohort comprised 41,291 adults undergoing chest CT during routine Korean health checkups (2002-2019). Emphysema was a binary variable from structured radiology reports, and the primary outcome was all-cause mortality via national death-registry linkage. The primary analysis was a complete-case Cox model adjusted for age, sex, BMI, and smoking status; sensitivity analyses used multiple imputation, ever-smoker restriction, scanner-era adjustment, a time-varying exposure, and competing-risks models.
RESULTS: Emphysema was present in 3,774 participants (9.1%), rising from 2.6% in never-smokers to 14.6% in current smokers; over a median of 8.5 years, 284 deaths occurred. Emphysema was associated with all-cause mortality in the designated complete-case analysis (HR, 1.54; 95% CI, 1.05-2.25), among ever-smokers after pack-years adjustment (1.63; 1.09-2.43), and when exposure was updated at repeat imaging (1.69; 1.18-2.41). Full-cohort pack-years imputation was non-significant (1.36; 0.97-1.91), diluted by never-smokers, among whom no participant with emphysema died. An exploratory cancer signal (HR, 2.25) was concentrated in lung cancer (13 events). Adding emphysema to a smoking-inclusive model improved discrimination by ≤0.004.
INTERPRETATION: Among ever-smokers, incidental emphysema on screening chest CT is associated with mortality after adjustment for pack-years, although residual smoking-intensity confounding cannot be excluded. Once smoking history is known, the report adds almost nothing to discrimination and should not be used alone to stratify prognosis; whether it should prompt evaluation for undiagnosed COPD we did not address. In the full screening population the association did not reach significance, but with 284 deaths, half the number needed for 80% power, that result is inconclusive rather than negative.
CLINICAL TRIAL REGISTRATION: Not applicable (observational retrospective cohort study).