Self-reported physician-diagnosed chronic obstructive pulmonary disease and spirometry patterns in Vietnam Era US Army Chemical Corps veterans: A retrospective cohort study

Abstract

Background: Research on chronic obstructive pulmonary disease (COPD) and herbicide exposure in Vietnam War veterans is limited.

Methods: Survey data were collected from 3193 US Army Chemical Corps veterans on herbicide exposure and self-reported physician-diagnosed COPD. Three spirometric patterns were used to define airflow obstruction (AFO): (i) FEV₁ /FVC < 70% ("fixed ratio"); (ii) FEV₁ /FVC < lower limit of normal ("LLN"); and (iii) (FEV₁ /FVC < LLN and FVC ≥ LLN and FEV₁ <LLN) or (FEV₁ /FVC<LLN and FEV₁ ≥ LLN) ("specific obstruction"). Associations between herbicide exposure and self-reported COPD and spirometric-AFO were determined using regression.

Results: COPD prevalence varied (self-reports: 20.1%; spirometry: 29.8%, 12.9%, 8.4% by fixed ratio, LLN, and specific obstruction definitions, respectively). Spirometric parameters did not differ by exposure. Self-reported COPD and herbicide exposure were significantly associated (adjusted odds ratio [aOR] = 1.82, 95% confidence intervaI: 1.48,2.24). No association was found between spirometric-AFO and herbicide exposure.

Conclusions: A significant association was found between herbicide exposure and self-reported physician-diagnosed COPD but not when COPD diagnosis was based on spirometry.

Keywords: COPD; Vietnam war; herbicides; spirometry.