Mortality Rates in Smokers and Nonsmokers in the Presence or Absence of Coronary Artery Calcification

Abstract

Objectives To further study the interplay between smoking status, Coronary Artery Calcium (CAC) and all-cause mortality. Background Prior studies have not directly compared the relative prognostic impact of CAC in smokers versus non-smokers. In particular, while zero CAC is a known favorable prognostic-marker, whether smokers without CAC have as good a prognosis as non-smokers without CAC is unknown. Given computed tomography (CT) screening for lung cancer appears effective in smokers, the relative prognostic implications of visualizing any CAC versus no CAC on such screening also deserve study. Methods Our study cohort consisted of 44,042 asymptomatic individuals referred for non-contrast cardiac CT (age 54±11 years, 54% males). Subjects were followed for a mean of 5.6 years. The primary endpoint was all-cause mortality. Results Approximately 14% (n=6020) of subjects were active smokers at enrollment. There were 901 deaths (2.05%) overall, with increased mortality in smokers vs. non-smokers (4.3% vs. 1.7%, p<0.0001). Smoking remained a risk factor for mortality across increasing strata of CAC scores (1-100, 101-400, and >400). In multivariable analysis within these strata, we found mortality hazard ratios (HRs) of 3.8 (95% CI, 2.8-5.2), 3.5 (2.6-4.9), and 2.7 (2.1-3.5), respectively, in smokers compared to nonsmokers. At each stratum of elevated CAC score, mortality in smokers was consistently higher than mortality in non-smokers from the CAC stratum above. However, among the 19,898 individuals with CAC=0, the mortality HR for smokers without CAC was 3.6 (95% CI, 2.3-5.7), compared to non-smokers without CAC. Conclusion Smoking is a risk factor for death across the entire spectrum of subclinical coronary atherosclerosis. Smokers with any coronary calcification are at significantly increased future mortality risk than smokers without CAC. However, the absence of CAC may not be as useful a “negative risk factor” in active smokers; as this group has mortality rates similar to non-smokers with mild to moderate atherosclerosis.

Prognostic utility of coronary artery calcium scoring in active smokers: A 15-year follow-up study

“…Our findings are consistent with prior studies of shorter duration demonstrating increased mortality in smokers with CAC. 2,3 Furthermore, in contrast to the general population for which the absence of CAC (CAC=0) is associated with an excellent prognosis, 5 in our study smokers with a CAC=0 remained at an elevated risk of death. As such, for smokers a CAC=0 should not be considered a “negative risk factor.” 3 …”

“…1 Prior research has demonstrated a higher rate of five to ten year estimated all-cause mortality in smokers with CAC as compared to smokers without CAC. 2,3 However, previous studies have produced limited insight regarding the long-term efficacy of CAC for risk stratification in smokers. This study therefore sought to examine the association between smoking, CAC, and all-cause mortality over a 15-year period.…”

“…CAC measurement was performed by electron beam computed tomography (EBCT) at three different centers in the United States using standard methods as previously described. 3 Each calcified lesion was scored using the method developed by Agatston et al 4 All individuals provided informed consent for a pre-test interview, CAC testing, and follow-up. The study received approval from the appropriate Human Investigations Committee and conforms to the 1975 Declaration of Helsinki.…”

Predictive Factors of the Presence and Number of Noncalcified Coronary Plaque in Japanese Patients with Zero Coronary Artery Calcium Score Using 64-Slice Multi-Detector Computed Tomography

“…Although in the present study, these predictors were the same as those of the presence of NCP, another predictor, a current smoking habit was one of the independent predictors of ≥ 2 NCPs. A recent study has demonstrated that smokers with zero CACS have higher relative mortality than nonsmokers with zero CACS [31]. Our results suggest that smoking might lead to coronary plaque progression, resulting in an increased risk of mortality in the patients with zero CACS.…”

Lifestyle Factors and Coronary Artery Calcification

“…Cigarette smoking is also associated with endothelial dysfunction by elevating platelet aggregability, fibrinogen levels, endothelial permeability and plasma viscosity and by lowering HDL cholesterol [38]. Approximately 50-62% of smokers have CAC scores of >0 [39,40]. The CARDIA study and the Heinz Nixdorf Recall study have shown that current smoking was positively associated with CAC [41,42].…”