Abstract Introduction Previous literature links Agent Orange exposure and idiopathic pulmonary fibrosis (IPF) in Veterans, but findings could be impacted by recall bias. We evaluated Veterans diagnosed with pulmonary fibrosis including those with true IPF, those with other ILD, and those without actual disease to assess the association of exposures with ILD. Methods We performed a secondary analysis of a published Veteran cohort who received ICD-9 diagnosis of pulmonary fibrosis between 1 January 2008 and Oct 2015. We stratified cases into IPF, other forms of fibrotic ILD, or no ILD. We excluded 59 cases of asbestosis, an established exposure-related ILD. We evaluated whether cases had a flag for military or occupational exposures, stratified into Agent Orange exposure or any other exposure. We compared exposure rates by ILD type using standardized mean differences (SMD) and chi-squared testing. We used cox modeling to assess the association of exposure with survival, stratified by ILD type (IPF versus other ILD). Results We identified N = 3,234 Veterans with pulmonary fibrosis diagnoses (excluding asbestosis); after chart review, Veterans were stratified into 1,880 with IPF, 475 with another ILD, and 879 without any ILD. Relative to Veterans without ILD, Veterans with IPF were more likely to be older, male, and White; conversely, Veterans with other ILD were more likely to be younger, female, and non-White. Table 1 shows rates of exposure by ILD type. For Agent Orange, exposure rates were similar between those with IPF (15.2%), other fibrotic ILD (14.3%), and no ILD (16.4%, SMD = 0.024, p = 0.549). For all others, occupational exposure was moderately but significantly higher in those with IPF (4.5%) compared with those with other fibrotic ILD (0.6%) and no ILD (0.5%, SMD = 0.248, p 0.001). In survival analysis, Agent Orange exposure was associated with improved survival in those with IPF (HR = 0.57-0.85, p 0.01) but not for other ILD (HR = 0.84-1.95, p = 0.25). Occupational exposure was not associated with survival in those with IPF (HR 0.53-1.11, P = 0.159) and could not be assessed in those with other ILD. Conclusions Occupational exposure has a complex association with ILD. Agent Orange was not associated with incidence of IPF or ILD but was associate with survival in IPF. Other occupational exposures were associated with IPF diagnosis but not survival, possibly due to low power. Further work is needed to better understand the complex relationship between Veteran exposures and pulmonary fibrosis. This abstract is funded by: Boehringer Ingelheim
Guidot et al. (Fri,) studied this question.