Etiologies and Characteristics of Interstitial Lung Disease in an Active-Duty Military Population

Abstract

Background: Interstitial lung diseases (ILD) are a unique group of lung disease that carries significant morbidity and mortality with increased incidence and prevalence with age. The heterogeneity and evolution of diagnosis has made defining true incidence and characteristics of disease difficult. This study aims to describe the etiology and characteristic in a young healthy military population with various deployment exposures.

Methods: A retrospective chart review was conducted using the electronic medical record for active duty service members with a diagnosis of ILD. Basic demographic data, diagnosis, pulmonary function testing, chest imaging, and pathologic results were reviewed. The groups were then subdivided for further analysis based on exposure and deployment history. Further subgroup analysis was performed on the major idiopathic interstitial pneumonias (IIP) and connective tissue disease-related ILD (CTD-ILD) within this cohort.

Results: Initial review of medical records identified 323 individuals with a diagnosis of ILD of which only 158 were analyzed. The cohort was 70.9% male with a mean age of 38.9 y. Chest imaging was performed in 158 (100%) patients while PFTs were done in 147 (93%) patients. Average FVC 3.52 L (77% predicted), FEV₁ 2.75 L (75% predicted), FEV₁/FVC 79%, TLC 6.32 L (78% predicted), and D_LCO 18.8 mL/Hg/min (63% predicted). Tissue diagnosis was made in 39.2 % of patients. BAL was performed in 20.9% of patients. Notably, 82 (51.9%) individuals were under the age of 40 while the remaining 76 (48.1%) over 40 years old. 32.3% had a diagnosis characterized as a major IIP, 29.7% with CTD-ILD, and 38% alternative diagnosis. There was a notably higher proportion of females in CTD-ILD subgroup when compared to major IIPs (44.7% vs 21.6%).

Conclusions: In this study we describe the etiology and characteristics of active duty military members diagnosed with ILD during military service. Despite a young population a variety of causes were found for underlying ILD. A higher proportion of females were noted to have CTD-ILD when compared to other subgroups. PFT data reviewed showed more subtle changes suggestive of early ILD. ILD is typically diagnosed later in life and early detection may help decrease long-term morbidity and mortality. Further investigation should be performed to evaluate any relationship of ILD to deployment or other exposures during military service.