OBJECTIVE: The aim of this study was to investigate whether smokers with incidental findings of interstitial lung abnormalities have an increased mortality during long-term follow-up, and review the contributing causes of death.

METHODS: Baseline CT scans of 1990 participants from the Danish Lung Cancer Screening Trial were qualitatively assessed for predefined interstitial lung abnormalities of any severity. Inclusion criteria for this lung cancer screening trial included current or former smoking, > 20 pack-years, and age 50-70 years. Patients were followed up for up to 12 years.

RESULTS: We found interstitial lung abnormalities in 332 participants (16.7%). Interstitial lung abnormalities were associated with increased all-cause mortality in the full cohort (HR: 2.0, 95% CI: 1.4-2.7, P < 0.001) and in lung cancer-free participants (HR: 1.6, 95% CI: 1.1-2.4, P = 0.007). The findings were associated with death from lung cancer (HR: 3.2, 95% CI: 1.7-6.2, P < 0.001) and non-pulmonary malignancies (HR: 2.1, 95% CI: 1.1-4.0, P = 0.02). Participants with fibrotic and non-fibrotic interstitial lung abnormalities had similar survival.

CONCLUSION: Interstitial lung abnormalities were common in this lung cancer screening population of relatively healthy smokers and were associated with mortality regardless of the interstitial morphological phenotype. The increased mortality was partly due to an association with lung cancer and non-pulmonary malignancies.