Subclinical atherosclerosis, airflow obstruction and emphysema: the MESA Lung Study

Abstract

Airflow obstruction is an independent risk factor for cardiovascular events in the general population. The affected vascular bed and contribution of emphysema to cardiovascular risk are unclear. We examined whether an obstructive pattern of spirometry and quantitatively defined emphysema were associated with subclinical atherosclerosis in the carotid, peripheral and coronary circulations. The Multi-Ethnic Study of Atherosclerosis recruited participants aged 45-84 yrs without clinical cardiovascular disease. Spirometry, carotid intima-media thickness (IMT), ankle-brachial index (ABI) and coronary artery calcium (CAC) were measured using standard protocols. Percentage of emphysema-like lung was measured in the lung windows of cardiac computed tomography scans among 3,642 participants. Multiple linear regression was used to adjust for cardiac risk factors, including C-reactive protein. Decrements in forced expiratory volume in 1 s (FEV(1)) and FEV(1)/forced vital capacity ratio were associated with greater internal carotid IMT, particularly among smokers (p=0.03 and p<0.001, respectively) whereas percentage emphysema was associated with reduced ABI regardless of smoking history (p=0.004). CAC was associated with neither lung function (prevalence ratio for the presence of CAC in severe airflow obstruction 0.99, 95% CI 0.91-1.07) nor percentage emphysema. An obstructive pattern of spirometry and emphysema were associated distinctly and independently with subclinical atherosclerosis in the carotid arteries and peripheral circulation, respectively, and were not independently related to CAC.

Figure 1

Multivariate relationships of upper-lobe emphysema to measures of subclinical atherosclerosis in the carotid, peripheral and coronary vascular beds. Multivariate relationships of upper-lobe emphysema to the intima-media thickness of the internal carotid artery (P=0.003), ankle-brachial index (P=0.004), prevalence of coronary artery calcium (P=0.29). Multivariate models adjusted for age, gender, race/ethnicity, smoking status, pack-years, urine cotinine, educational attainment, diabetes mellitus, fasting plasma glucose, height, body mass index, alcohol use, hypertension, systolic and diastolic blood pressure, C-reactive protein, LDL, HDL, statin medication, alcohol use, scanner type and mAs. The relationship of upper-lobe emphysema to the intima-media thickness of the internal carotid artery was non-linear (P=0.002), although those ankle-brachial index and prevalence of coronary artery calcium were not (P=0.12, P=0.45, respectively). Thick lines = smoothed regression lines, which allows for non-linear relationships; thin lines = 95% confidence intervals.