Pleural abnormalities in the Framingham Heart Study: Prevalence and CT image features

Background: The prevalence of pleural abnormalities in the general population is an epidemiologically important index of asbestos exposure, which has not been investigated since a radiography-based study in 1980. Methods: We examined 2633 chest CT scans (mean 59.2 years, 50% female) from the Framingham Heart Study (FHS) for the presence and image characteristics of pleural plaques and diffuse pleural thickening. Demographics and pulmonary function were stratified by the presence of pleural abnormalities in association with interstitial lung abnormalities. Results: Pleural abnormalities were present in 1.5% (95% CI 1.1% to 2.1%). Pleural lesions were most commonly bilateral (90.0%), multiple (77.5%), calcified (97.5%) and commonly involved posterior (lower: 92.5%, middle: 87.5%), anterior (upper: 77.5%, middle: 77.5%) and diaphragmatic areas (72.5%). Participants with pleural abnormalities were significantly older (75.7 years, p < 0.0001), male (92.5%, p < 0.0001), former or current smokers (80.0%, p < 0.001) with higher packyears (33.3, p < 0.0001). No significant reduction was noted in pulmonary function measures (p=0.07-0.94) when adjusted for the associated covariates, likely due to small number of cases with pleural abnormalities. Information about prior history of asbestos exposure and occupation was not available. Conclusions: Pleural plaques and diffuse pleural thickening are present on CT in 1.5% of the FHS cohort. The current prevalence of the pleural abnormalities is smaller than that reported in the previous populationbased study using chest radiography, likely representing lower asbestos exposure in recent decades. The posterior portion of the pleura is most frequently involved but the anterior portion is also commonly involved.