Per cent emphysema is associated with respiratory and lung cancer mortality in the general population: a cohort study.

Background: Emphysema on CT is a risk factor for all-cause mortality in persons with and without airflow obstruction; however, causes of death associated with emphysema remain uncertain, particularly in the general population.

Aims: To test associations between quantitatively assessed emphysema on CT and cause of death in persons with and without a substantial smoking history.

Methods: The Multi-Ethnic Study of Atherosclerosis recruited 6814 participants, aged 45-84 years and without clinical cardiovascular disease, in 2000-2002. Per cent emphysema was defined on cardiac CT as per cent of lung voxels less than -950 Hounsfield units; emphysema on CT was defined as per cent emphysema above the upper limit of normal. Cause of death was classified by administrative codes. Proportional-hazards models were adjusted for age, race/ethnicity, gender, body mass index, smoking status, pack-years, coronary artery calcium, site and education. Additional adjustment for lung function was made in a subset with spirometry from 2004 to 2006.

Results: There were 1091 deaths over 12 years median follow-up. Emphysema on CT was strongly associated with increased mortality due to respiratory diseases (adjusted HR 2.94, 95% CI 1.68 to 5.15), particularly chronic lower respiratory diseases (adjusted HR 9.54, 95% CI 4.70 to 19.35), and lung cancer (adjusted HR 1.84, 95% CI 1.09 to 3.12), but not cardiovascular disease. Associations persisted among participants with fewer than 10 pack-years and those without physician-diagnosed respiratory disease, and were similar after adjustment for airflow measures and in persons without airflow limitation.

Conclusions: Quantitatively assessed emphysema on CT is associated with greater respiratory disease and lung cancer mortality, even among persons without traditional risk factors.