Higher mortality rates found in smokers with CAC

Smokers with coronary artery calcification face higher mortality rates than smokers without coronary artery calcification, but its absence does not necessarily decrease the risk for death in smokers until smoking has been ceased, researchers said in an article recently published in the Journal of the American College of Cardiology: Cardiovascular Imaging. The study cohort was composed of 44,042 participants without symptoms and who were referred for noncontrast cardiac CT.

The mean age of the participants was 54 years; 54% were men and 6,020 (13.7%) were smokers at enrollment. The participants were followed for a mean of 5.6 years, and the primary endpoint was all-cause mortality. Data on cardiac-specific mortality are not available. There were 901 all-cause deaths, with increased mortality among smokers vs. nonsmokers (4.3% vs. 1.7%; P<.0001). Smoking was found to be a risk factor for mortality across increasing strata of coronary artery calcification (CAC) scores (1 to 100, 101 to 400, and >400).

Mortality was consistently higher in smokers compared with nonsmokers at each stratum of elevated CAC score. A multivariable analysis within these strata produced HRs of 3.8 (95% CI, 2.8-5.2), 3.5 (95% CI, 2.6-4.9) and 2.7 (95% CI, 2.1-3.5), respectively, for smokers vs. nonsmokers. Researchers also found that smokers without CAC had mortality rates similar to nonsmokers with mild-to-moderate atherosclerosis. HR for smokers without CAC was 3.6 (95% CI, 2.3-5.7) compared with nonsmokers without CAC.

 “Smoking is an important mortality risk factor across the entire spectrum of subclinical atherosclerosis, including those with CAC=0. The absence of CAC in smokers should not be regarded as a ‘negative risk factor’ until smoking cessation occurs. Despite this, coronary artery calcification remains an excellent way of risk stratifying both nonsmokers and smokers. Whether CAC quantification can motivate smoking cessation efforts deserves future study. Our data reinforce the notion that all smokers, including those without subclinical coronary atherosclerosis but especially those with increased CAC, should be strongly encouraged to quit,” the researchers said.