Risk factors for interstitial lung disease: a 9-year Nationwide population-based study

Background: Understanding the risk factors that are associated with the development of interstitial lung disease might have an important role in understanding the pathogenetic mechanism of interstitial lung disease as well as prevention. We aimed to determine independent risk factors of interstitial lung disease development. Methods: This was a retrospective cohort study with nationwide population-based 9-year longitudinal data. We selected subjects who were aged >40 years at cohort entry and with a self-reported history of cigarette smoking. Cases were selected based on International Classification of Diseases codes. A cohort of 312,519 subjects were followed until December 2013. We used Cox regression analysis to calculate the hazard ratios (HRs) for interstitial lung disease development. Results: Interstitial lung disease developed in 1972 of the 312,519 subjects during the 9-year period. Smoking (HR: 1.2; 95% confidence interval [CI]: 1.1-1.4), hepatitis C (HR: 1.6; 95% CI: 1.1-2.3), history of tuberculosis (HR: 1.5; 95% CI: 1.1-1.9), history of pneumonia (HR: 1.6; 95% CI: 1.3-2.0), and chronic obstructive pulmonary disease (HR: 1.8; 95% CI: 1.6-2.1), men (HR: 1.9; 95% CI: 1.7-2.1) were significantly associated with the development of interstitial lung disease. The risk of interstitial lung disease development increases with age, and the risk was 6.9 times higher (95% CI: 5.9-8.0) in those aged over 70 than in their forties. Conclusions: Smoking, hepatitis C, history of tuberculosis, history of pneumonia, chronic obstructive pulmonary disease, male sex, and older age were significantly associated with interstitial lung disease development.