RATIONALE: Cigarette smoke exposure is a risk factor for many lung diseases, and histologic studies suggest tobacco-related vasoconstriction and vessel loss plays a role in the development of emphysema. However, it remains unclear how tobacco affects the pulmonary vasculature in general populations with a typical range of tobacco exposure, and whether these changes are detectable by radiographic methods.
OBJECTIVE: To determine whether tobacco exposure in a generally healthy population manifests as lower pulmonary blood vessel volumes and vascular pruning on imaging.
METHODS: 2,410 Framingham Heart Study participants with demographic data and smoking history underwent volumetric whole-lung computed tomography (CT) from 2008-2011. Automated algorithms calculated the total volume of all intrapulmonary vessels (TBV), smaller peripheral vessels (BV5), and the relative fraction of small vessels (BV5/TBV). Tobacco exposure was assessed as smoking status, cumulative pack-years, and second-hand exposure. We constructed multivariable linear regression models to evaluate associations of cigarette exposure and pulmonary blood vessel volume measures, adjusting for demographic covariates including age, sex, height, weight, education, occupation, and median neighborhood income.
RESULTS: All metrics of tobacco exposure (including smoking status, pack-years, and second-hand exposure) were consistently associated with higher absolute pulmonary blood vessel volume, higher small vessel volume, and/or higher small vessel fraction. For example, ever-smokers had a 4.6mL higher TBV (95% CI: 2.9-6.3, p<0.0001), 2.1mL higher BV5 (95% CI: 1.3-2.9, p<0.0001), and 0.28 percentage-point higher BV5/TBV (95% CI: 0.03-0.52, p=0.03) compared to never-smokers. These associations remained significant after adjustment for percent-predicted FEV, cardiovascular comorbidities, and did not differ based on presence or absence of airflow obstruction.
CONCLUSIONS: Using CT imaging, we found that cigarette exposure was associated with higher pulmonary blood vessel volumes, especially in the smaller peripheral vessels. While histologically, tobacco-related vasculopathy is characterized by vessel narrowing and loss, our results suggest that radiographic vascular pruning may not be a surrogate of these pathologic changes.