Impact of exercise maintenance on mortality in interstitial lung disease: a population-based retrospective cohort study

Background: Previous studies have proposed exercise capacity as a mortality predictor in individuals with interstitial lung disease (ILD). However, limited information is available regarding whether maintaining exercise is associated with improved survival in individuals with ILD. Objectives: We aimed to evaluate the association between exercise maintenance and mortality in individuals with ILD using a longitudinal, large population-based database. Design: This retrospective cohort study used the Korean National Health Insurance claims-based database. Methods: We analyzed a total of 3850 individuals with ILD who underwent two consecutive health screening examinations. The study exposure was the change in exercise habits between the two examinations, with individuals classified as exercisers (exercise maintainers and exercise non-maintainers) or non-exercisers. The primary outcome was mortality. We adjusted for age, sex, body mass index (BMI), smoking status, alcohol status, economic status, residential area, and comorbidities. Results: During a median follow-up of 7.2 (interquartile range, 5.6–9.2) years, the incidence rate of death for exercisers was lower than that of non-exercisers (341.28 per 10,000 person-years (PY) vs 401.81 per 10,000 PY). Multivariable Cox regression analysis showed that the risk of mortality was substantially lower in exercisers compared to non-exercisers (adjusted hazard ratio (aHR): 0.82, 95% confidence interval (CI): 0.72–0.94). The risk of reduction for death was correlated with exercise adherence, with the lowest risk among exercise maintainers (aHR: 0.78 (0.66–0.92)) followed by exercise non-maintainers (aHR: 0.85 (0.73–0.99)), compared to non-exercisers. In subgroup analyses, BMI and economic status had a significant interaction in the association between exercise and mortality. The risk of death was lower in individuals with a lower BMI and higher economic status compared to their counterparts. Conclusion: Among individuals with ILD, the risk of death was inversely correlated with the level of exercise adherence, cautiously suggesting the importance of exercise maintenance in individuals with ILD.